

Transcript of video below:
Hi there, my name is Paul, and this is Exposure Therapy. In this video, I’ll teach you about one of the most fundamental concepts in photography — the photographic stop. The stop is ubiquitous — it’s everywhere — and understanding it will make you an efficient photographer. However, to learn why the stop is so vital, we need to establish a foundation of knowledge about the basics of exposure and reciprocity law. These will be our first topics, so let’s begin!
Exposure is the total amount of light used by your camera’s image sensor to make a photo. It has a direct influence on the brightness of your pictures. The total exposure, that is, the “volume” of light received by the sensor is determined by two factors: the intensity of light passing through the lens and the time duration of that exposure. The following equation shows this relationship:
Exposure = Intensity × Time
The aperture controls the intensity of light. It’s a variable-sized circular opening found inside most lenses. Meanwhile, the shutter controls duration, being the accumulation of light over a period of time. On your camera, the aperture and shutter are the only settings for controlling the total amount of light reaching the sensor.
A third element, called ISO, is an electronic function that simulates changes to exposure but without adding or subtracting light. In other words, adjusting the ISO changes the brightness of your picture without changing the exposure. Together, the aperture, shutter, and ISO control what I call the Effective Exposure, that is, the brightness of your picture. It’s expressed with the following equation:
Effective Exposure = Intensity × Time × ISO
These equations reveal a common bond between the exposure controls. Reciprocity represents the relationship both intensity and duration have on the resulting exposure. That’s because many combinations of intensity and duration can produce photos with identical exposures. Even more combos of intensity, duration, and ISO can make photos with the same effective exposures.
To get a better sense of reciprocity, let’s take a moment to consider pure math. Consider the number 100. It’s the product of 50×2. But it can also be the product of 25×4, 20×5, 10×10, or 2×5×10. There are many different equations that equal 100.
The same principle applies to light and photography. Several combinations of aperture and shutter speed can produce the same total exposure. For example, you can achieve the same total exposure using an aperture value of ƒ/16 and shutter speed of 1/250 second, or ƒ/11 and 1/500 second, or even ƒ/5.6 and 1/2000 seconds; all three permutations produce equivalent exposures.
Students attending my beginner courses get this concept quickly but question its usefulness—what’s the point of making these adjustments if the exposure remains unchanged? The point is artistic.
Although the primary purpose of the aperture and shutter is to regulate exposure and picture brightness, they have secondary characteristics that can change the artistic appearance of your photograph, giving it a distinct character.
If you’re happy with your exposure in terms of brightness but not in terms of the depth of field—say you want more dramatic focus separation—you can increase the size of the aperture. This change increases the light intensity passing through your lens, raising the exposure and making your picture brighter than originally intended. To compensate, you’d simply select a faster shutter duration; this change decreases the exposure by an amount equal to the change you made to the aperture.
It seems easy, right? You’ve made a change that added one quantity of light, and then subtracted an equal amount of light to balance the exposure.
However, there’s a complication: different units of measure express your exposure settings. F‑numbers express the aperture, time units express the shutter speed, and ISO is a unit itself. So how do we reconcile changes between f‑numbers, duration, and ISOs?
We do it with the photographic stop, which unifies everything.
In photography, a stop is a unit that describes the change or difference between exposure values. Adding one stop doubles your exposure, but subtracting one stop halves your exposure. Therefore, a stop multiplies or divides your exposure by two depending on whether you’re adding or subtracting light. (And remember, multiplying by half is the same as dividing by two.)
You can add or subtract multiple stops. For example, adding two stops doubles your exposure and doubles it again, which creates an exposure four times brighter than the original (because 2 × 2 = 4). Conversely, subtracting three stops halves your exposure, then halves it again, and halves it a third time, which creates an exposure that’s one-eighth as bright as the original (because ½ × ½ × ½ = ⅛).
The photographic stop reconciles how changes to the aperture, shutter speed, and ISO affect the balance of exposure and picture brightness. Virtually every camera shows the degree of change applied to each setting using stops or fractions of stops.
You can check this on your camera right now. Grab your camera, select Shutter Priority mode, and rotate the command dial to adjust the shutter speed. By default, most cameras will make a one-third stop change to the value for every detent (or click) of the wheel’s rotation. So, for example, if you start at 1/500 seconds and rotate the dial by three clicks towards the faster direction, you’ll arrive at 1/1000 seconds. These two values differ by one stop—minus one stop if moving from 1/500 to 1/1000 because that change halves the light, and adding one stop if moving from 1/1000 to 1/500 because that change doubles the light.
Now try it with f‑numbers. Set your camera to Aperture Priority mode and count the clicks between ƒ/8 and ƒ/16. It’s six clicks on most cameras, representing a change of two stops because each click of the wheel applies a one-third stop change. Whether the shift is plus or minus two stops depends entirely on whether you’re adding light by moving towards lower f‑numbers or subtracting light by moving towards higher f‑numbers.
In practice, these changes won’t impact your exposure because both priority modes are automatically exposed. The camera balances your inputs by automatically applying an inverse transformation to the setting it controls. However, your camera can sometimes misread the scene and produce poor auto exposures. You can fix these errors with exposure compensation, which lets you raise or lower the standard exposure set by the camera. A numeric scale expresses changes in exposure compensation, and the change to exposure between each adjacent number is one stop. Most cameras allow you to adjust exposure compensation from ±2 to ±5 stops in one-third stop increments. Note that some camera makers refer to the numbers expressing exposure compensation as “EV.” EV stands for Exposure Value, and in this sense, they’re synonymous with stops.
Understanding the concept of photographic stops is essential when setting exposures manually and lets you quickly determine the ideal balance of the aperture, shutter speed, and ISO.
Let’s pretend we’re outside on a sunny afternoon and want to capture a portrait. We can quickly obtain good exposure by using the Sunny 16 rule of thumb. It states we can get an accurate exposure in direct sunlight by setting our aperture to ƒ/16 and selecting a shutter speed that inversely matches the ISO value. Therefore, ISO 100 would correspond to a shutter speed of 1/100 second, and ISO 400 would match with a shutter speed of 1/400 second, and so on.
Let’s take this rule of thumb and apply it to that daylight portrait. Our starting exposure values are ƒ/16, 1/200 second, and ISO 200. However, portraits generally benefit from a shallow depth of field because it creates a visual separation between the subject and their background, and an aperture of ƒ/16 isn’t ideal for this goal. Let’s choose ƒ/5.6 instead because it accomplishes the effect and is achievable by most lenses. It takes nine clicks of the control dial to move the aperture from ƒ/16 to ƒ/5.6, and this translates to a three-stop increase in light intensity. If we were to take a picture now, our exposure would be three stops (that is, eight times) too bright. Since our change to the aperture adds light, we must subtract an equal amount of light from the remaining values to balance our exposure. To remove three stops of light from the shutter, we must turn the shutter control dial nine clicks towards the faster direction, which results in a shutter speed of 1/1600 second. Thus, we replaced our starting exposure values of ƒ/16, 1/200 second, and ISO 200 with ƒ/5.6, 1/1600 second, and ISO 200. This change adds three stops on the aperture and subtracts three stops from the shutter speed, which makes the net difference zero. It imposes a dramatic visual change without altering the effective exposure.
Now let’s see what happens when we add ISO to the mix. Reset the camera to the original rule of thumb settings: ƒ/16, 1/200 second, and ISO 200. We’ll again choose ƒ/5.6 for the shallower depth of field. However, we’ll now split the balance between the shutter and ISO. We’ll subtract one stop from the ISO by moving from 200 to 100. This makes our picture one stop darker. To remove the remaining two stops of light from the shutter, we’ll turn the shutter control dial six clicks towards the faster direction, resulting in a shutter speed of 1/800 second. Thus, we’ve replaced our starting exposure values with ƒ/5.6, 1/800 second, and ISO 100. This change adds three stops of light on the aperture, subtracts two stops of light from the shutter speed, and removes one stop of brightness from the ISO, creating a net difference of zero stops.
The underlying notion of stops—the act of multiplying or dividing by two—is ubiquitous throughout all facets of photography beyond adjusting exposure compensation and balancing manual mode. For example, stops express the output power of built-in and external flash units. The output on my ProPhoto D1 is adjustable in full stops or one-tenth stop increments. Stops also indicate how much light is lost to colour, polarizing, and neutral density lens filters and light modifying gels. Camera makers use stops to specify the effectiveness of optical and in-body image stabilization systems. And once the camera and lights are off and you’re in the digital darkroom, editing applications like Adobe Lightroom and Capture One Pro use stops to represent the scale of their exposure adjustment sliders.
This shows that stops are inescapable. Reinforcing your understanding and internalizing that knowledge through practice will help you become an efficient photographer. And all it takes is knowing how to multiply or divide by two.
I hope you enjoyed this video and found it helpful. If you have requests for future topics, let me know in the comments, and I’ll consider them for future videos. In the meantime, you can learn more about photography or join my group photography courses in Toronto by visiting ExposureTherapy.ca. See you next time.
The following article is a transcript of the video above.
Hi there, my name is Paul, and this is Exposure Therapy. In this video, I’ll explain why your photos of the moon are often overexposed and how you can fix them.
I teach group photography workshops, and occasionally, students will ask some variation of the following question:
I tried taking a picture of the full moon last week, but it turned out too bright and featureless. How do I take photos of the Moon, so it looks similar to how my eyes see it?
My typical (and slightly cheeky) response is to point out that it’s sunny on the moon. Then I wait for a beat or two to let it sink in.
Is it sinking in for you?
Let’s begin with the basics. The moon and the sun are the most prominent celestial bodies in the sky. An important distinction between the two is the nature of their light. The sun radiates its light—it glows. It’s similar to the flames of a fire, neon signs, and the tungsten filaments of lightbulbs. By contrast, moonlight is sunlight that has bounced off its surface to end up on Earth, both in our eyes and our cameras.
Conventionally, the most reliable way to get the “correct” exposure of subjects that don’t glow is by using an incident light meter, such as this Sekonic that I’ve had for 15 years. These devices measure the amount of light falling on your subject. I walk up to my subject, point the white dome towards the camera, take a light reading, and the meter shows the correct exposure settings for the scene.
However, there’s an obvious flaw with this method: with its average orbital distance of about 385,000 km, one does not simply walk up to the moon.
So what do we do? We remember that it’s sunny on the moon. But let me qualify that statement.
Except for lunar eclipses, sunlight illuminates half of the moon’s surface at any given moment. However, there’s a daily change to the apparent shape of the sunlit portion of the moon as seen from Earth. These differences in appearance, known as lunar phases, occur because as the moon orbits the earth, we see varying amounts of its sunlit half.
The moon is not visible during the new moon phase when it’s roughly between the earth and the sun. The new moon is invisible because it’s in the same part of the sky as the sun, and its “near side” — the hemisphere that always faces the earth, regardless of phase — is in complete shadow.
As the moon continues its orbit, progressively more of its near side turns towards sunlight. First, it becomes a waxing crescent moon, then a first-quarter moon, followed by a waxing gibbous moon, culminating in a full moon.
During a full moon, Earth is roughly between the moon and sun. The full moon is completely visible because it’s opposite the sun in the sky, and the hemisphere of its near side is in full sunlight.
The lunar phases continue in reverse beyond the full moon as its near side gradually turns away from the sun. These phases are waning gibbous moon, last quarter moon, waning crescent moon, and then a new moon. The period from new moon to new moon marks an entire lunar month, which takes 29.53 days to complete, and is equivalent to a single day/night cycle on the moon.
We’ve established it’s sunny on the moon and that we see varying amounts of the sunlit hemisphere throughout a lunar phase cycle. But we still have the problem of not getting close enough to the moon to get an exposure reading. The solution, as earthbound photographers have figured out long ago, is taking an incident reading from somewhere that’s within reach and has light identical to their subject’s position.
It’s sunny on the moon, but it’s also sunny here on Earth. To take pictures, it’s entirely reasonable to assume that afternoon sunlight on Earth is identical in intensity to sunlight on the full moon. Therefore, exposure settings appropriate for direct afternoon sunlight on Earth will produce correct exposures of the full moon at night.
Anyone who’s tried taking photos of the moon at night using their camera’s automatic settings has probably found the results disappointing. Most automatic photos of the moon at night are irreparably overexposed, and there are two reasons why. First, the moon is hundreds of times brighter than the surrounding night sky. And second, although this brightness gives it visual prominence, its scale within most photographic compositions is relatively tiny at typical focal lengths. Together, these factors cause the camera to assume it’s taking a photo of something quite dark, and it compensates by letting in far more light than your intended subject requires, which washes out the moon.
The best way to get “correct” exposures of the moon at night is by taking complete control of your camera using manual mode. But what qualifies as a “correct” exposure?
Even when it’s not overexposed, many photos of the nighttime moon render it brighter than its true lightness. In astronomy, “albedo” describes the average surface reflectance of planets, moons, and asteroids. Albedo measures the fraction of incident light the surface reflects in all directions. The moon has an albedo of 0.12, which means it reflects just 12% of the Sun’s light. This translates to an average surface lightness described as slightly brighter than old asphalt. In comparison, Earth’s albedo averages to about 0.30. The photos taken by the crews of NASA’s Apollo landings show just how dark the lunar surface appears in comparison to the astronauts’ white spacesuits in direct sunlight.
The purpose of the Apollo photos was to create an accurate visual document of the lunar surface, its features, and of the astronauts and their equipment.
Since earthbound photographers don’t have such mission-critical constraints, we’re free to take creative license in our depictions of the moon. Some photographers choose accurate depictions. Others prefer representations that are brighter than true while ensuring surface details aren’t washed out. And a third group doesn’t care because their primary subject is something else, such as the moonlit landscape. Hence, every mention of “correct” exposures features scare quotes. I believe that within the art of photography, every exposure is correct so long as a result is intentional. An exposure is only wrong when the effect is undesirable.
The moon’s phase affects how bright it appears on Earth. The illuminated portion of the moon looks brightest during the full moon and darkest during the crescent moon. As our angle of view relative to the sun decreases, the moon’s highly crated and irregular surface forms a greater amount of shadows as seen by observers from Earth. This lowers the surface reflectance of the sunlit portion visible to us.
Additionally, the full moon appears brighter due to a phenomenon called opposition surge. It occurs when a rough surface appears brighter when the light source is directly behind the observer. The Apollo missions provide human-scale examples of this effect in their photos from the surface. The surge in brightness is quite subtle due to its gradation and the impact of colour constancy. The difference in brightness becomes rather stark when making a side-by-side comparison of two non-adjacent patches of lunar soil. In some photos, the effect is also noticeable on a small scale in the reflections of astronauts’ helmets. In this famous example, the opposition surge brightens the area around Buzz Aldrin’s shadow, as seen in his helmet’s reflection. And here, we see it in the reflection of David R. Scott’s shadow from Apollo 15. On a macro scale, the entire visible surface of the moon experiences an opposition surge of brightness during the full moon phase.
Regardless of the lunar phase, the moon’s brightness and colour are also affected by its altitude, which describes the apparent height of a celestial object above the horizon. It’s expressed in degrees, with the horizon at 0° and the zenith (directly overhead) at 90°.
The moon appears brighter at progressively higher altitudes. The sun exhibits the same characteristics: sunlight is harshest at solar noon and faintest at sunset. In both cases, the atmospheric scattering of light causes the effect.
Light scattering occurs when photons bounce off particles in their paths, such as atoms and molecules. Particles that are smaller than the wavelength of visible light are more effective at scattering the short-wavelength photons of blue light than the long-wavelength photons of red light.
Light scattering occurs at all altitudes. When the moon or sun is near the horizon — either rising or setting — the light reaching your eyes passes through a thick layer of the atmosphere, which scatters a far more significant amount of blue light than red. Since a large portion of their light is scattered away from a straight-line path to your eyes when they’re near the horizon, they appear redder. At higher altitudes, the moon’s light passes through a comparatively thin layer of the atmosphere, scattering just enough blue light to give the Moon its characteristic yellowish colour, distinct from the stark grey surface depicted in the Apollo photos.
As an interesting side note, if you’re an early bird, you’ve probably noticed that sunrises are less red than sunsets. That’s because there’s a greater propensity for stronger winds during the daytime, which helps lift dust particles into the atmosphere and scatters even more blue light. The same effect doesn’t necessarily apply to the setting and rising of the moon. I’ve personally witnessed many reddish moonrises; however, they’ve all occurred close to sunset, while dust permeated the local atmosphere.
All of this relates to taking photos of the moon. Exposure settings derived from mid-afternoon daylight are generally correct for pictures of a full-ish moon at an altitude of 45° or greater (that is, more than halfway up between the horizon and zenith). However, these settings will likely be incorrect for photos of the moon while it’s near the horizon since Earth’s atmosphere attenuates much of its brightness.
Have you ever gazed upon a crescent moon and realized that you could see details in its shaded portion?
Much as with the moon, some sunlight that strikes Earth’s surface and clouds reflects into space. This reflected light is called earthlight. The subtle illumination of the Moon’s dark side by earthlight is called earthshine. The distinction between these two terms can be confusing at first, but it’s all quite simple if illustrated with a diagram. Light from the sun is sunlight. Sunlight reflected by the earth is earthlight. Earthlight reflected off the moon’s dark side is earthshine. [Use a variant of this diagram: https://upload.wikimedia.org/wikipedia/commons/3/3f/Earthshine_diagram.png]
Earthshine is most prominently visible during the moon’s crescent phase. An observer standing on the moon’s near-side would see a very bright “gibbous Earth” against the black sky. At this point, you should come to the gradual realization that the moon experiences Earth in phases, and these phases are complementary. Thus, a new moon on Earth coincides with a full earth seen from the Moon, and so on. Earthshine peaks during the new moon but remains invisible because of the moon’s proximity to the sun in the daytime sky.
Taking photos of earthshine using your camera’s automatic mode should give decent results because earthshine is closer in brightness to the typical night or twilight sky. However, a single exposure can’t capture detail in both because the difference in brightness between earthshine and the sunlit portion of the moon is too significant. Against a dark sky, your camera will overexpose the crescent.
The point of this video is to explain the futility of a single solution. That’s because the moon’s brightness varies with its phases and altitude. Moreover, the accuracy of your exposure to the moon’s true lightness is also an artistic decision. The solution requires internalizing a fundamental principle: it’s sunny on the moon.
However, for those of you inclined to prescriptive recommendations, start with exposures appropriate for the full moon high in the sky and incrementally work your way down to dimmer moons.
Select manual shooting mode, and choose appropriate exposure settings for a subject in direct afternoon sunlight on earth. At ISO 200, this means selecting ƒ/5.6 and 1/2000s, or ƒ/8 and 1/1000s, or ƒ/11 and 1/500; all of these different settings produce the same exposure. When the moon is lower in the sky or during a minor phase, increase your exposure by selecting a lower f‑number or slower shutter speed, or both. Experience and practice using your camera make the process faster and easier. However, it would help if you started from the principle that it’s sunny on the moon.
I hope you found this video interesting and helpful. I enjoy talking my students through these types of questions instead of stating the correct settings without explaining why they’re right. If you have requests for topics, let me know in the comments, and I’ll consider them for future videos. In the meantime, you can learn more about photography or join my group workshops in Toronto by visiting ExposureTherapy.ca. See you next time.
This article combines the scripts from the two videos above into a single resource that shows you what to check when buying a used DSLR or mirrorless camera on Facebook Marketplace or Craigslist.
Buying a used DSLR or mirrorless camera is a great way to expand your kit on a budget, and the best value is typically found on Facebook Marketplace, Craigslist, and similar sites. However, a downside of buying a used camera directly from the owner is that you’re giving up the peace of mind offered by store refunds and manufacturer warranties in exchange for a lower price.
Since these deals involve cameras that are “final sale” and “as-is” — meaning, there’s no recourse if you find fault in them later — it’s essential to confirm the camera’s condition. Here’s the ultimate checklist of what to look for when buying a used DSLR or mirrorless camera in person.
Cameras can have quirks or manufacturing defects that are common to specific models. Do a web search to see if the model you’re interested in suffers from common issues and check for them during the inspection.
The software powering your camera is called firmware. Like all software, firmware can have bugs. Camera makers sometimes release firmware updates that fix bugs and add or expand software-based features. Firmware bugs can easily be confused for physical faults or defects, and so can the previous owners’ customizations. It’d be a shame to pass up an otherwise excellent camera because a bug fix wasn’t installed or a non-standard button assignment that wasn’t reset. You can avoid these pitfalls by asking the seller to update the firmware and reset the camera to defaults before you meet.
If the seller claims they’re in a rush and have somewhere else to be, there’s a good chance they’re hiding something and hoping that a cursory inspection will miss it. Always take as much time as necessary to conduct your assessment or terminate the deal. Don’t succumb to pressure; you don’t owe the seller any favours.
Open the battery compartment and remove the battery. On most modern cameras, the battery is spring-ejected upon release. A damaged or defective lithium battery can sometimes swell to a point where the spring cannot push it far enough to pull out. This is a sign the battery will need replacing.
Once the battery is removed, use your phone’s LED to inspect the electronic contacts inside the battery compartment for signs of corrosion or oxidation. I’d consider any damage a dealbreaker because it can cause shorts, power loss, and so forth.
Place the battery into the camera, ensure that it fits well and secures into place, close the compartment door, and turn the camera’s power on.
With the aid of your phone’s LED, check the slots for dust and damage. This is a critical check on cameras that use Compact Flash (CF) cards since they don’t physically prevent accidental sideways insertion, which could lead to bent pins. Always bring your own memory cards to check for compatibility. Make sure they lock into place, and the camera can read and write to them—you can snap a few photos to confirm.
Modern cameras have a variety of electronic terminals such as HDMI, USB, and audio ports. Because there are so many, it’s not always practical to check every port without the appropriate cables and connecting device on hand. Instead, perform a visual inspection of each terminal for dust, debris, and bent or broken pins. And when you’re buying a camera for a purpose that involves a specific terminal, definitely bring something to ensure it’s in working order.
Also, make sure to check the camera’s external flash hot shoe mount for corrosion. Some mounts may be covered by plastic tabs, so feel free to remove them. Better yet, bring any hot shoe-mounted flash and test it with the camera. While most flash units are designed to work with a specific camera system, virtually every contemporary camera can fire a hot shoe flash when taking a photo.
Pay attention to the condition of the plastic doors and rubber flaps that protect the terminals. Do they close flush with the camera body? Are the anchors attaching the rubber flaps in good shape? For cameras with “weather resistance,” check the condition of the rubber or foam seals on all doors and flaps.
A lens is attached to a camera using the mount, which provides a secure attachment point and ensures the lens and camera are correctly aligned. All camera lens mounts are metallic and take determination to damage.
The electronic contact pins found just beyond the interior edge of the lens mount facilitate communication with lenses. Ensure that the contact pins are clean, not bent, and don’t exhibit signs of corrosion. Remember to hold the camera face-downward while performing these checks to minimize dust entering the cavity.
The easiest way to confirm is by mounting your own compatible lens, ensuring it secures into place with an audible click. Although a tiny amount of rotational give is acceptable, the lens should fit tightly, and there shouldn’t be any tilting or sagging.
Confirm that the camera recognizes the lens by engaging the autofocus and adjusting the aperture. Take several photos while adjusting the aperture and focus location between each shot. Then, examine the pictures to confirm the changes.
When examining a DSLR, it’s crucial to check the primary components found in the mirror box. These include the mirror itself and the ground glass focusing screen onto which light from the mirror reflects to form the image seen in the viewfinder. The focusing screen is located at the roof of the mirror box. They should be free from water marks, dirt, and scratches. Hold the camera facing down when performing this check to minimize dust contamination.
There are two ways to check the image sensor. You can perform a direct visual inspection of the sensor itself, or you can check the photos it takes. I recommend doing both.
Performing a visual inspection is simplest on a mirrorless camera. Remove the lens or body cap from the camera, and look at the sensor inside. The easiest way to check a DSLR’s image sensor is by selecting a long exposure time in Shutter Priority mode—something like 30 seconds or longer—and “taking a picture” with the lens off. With the camera held face-down, examine the sensor with the aid of your phone’s LED. You should see a smooth iridescent surface that’s free from scratches and damage. Don’t be alarmed or disappointed if you see dust, as it’s completely normal and relatively easy to clean.
The second method of checking an image sensor is by taking a photo. To do this, select ƒ/16 or higher in Aperture Priority mode, then point the camera at a bright and featureless subject (such as the sky or a white wall) and take a shot. Blurry dots and specks are dust or grit, and blurry squiggles are fibres; blurry lines, especially longer and straighter ones, are likely scratches.
The shutter is a precision mechanism that’s crucial to the functionality of a camera. The estimated durability of a shutter is described by camera makers as shutter lifetime and expressed in shutter actuations, which is the number of times a shutter has fired. Generally, cameras with fewer shutter actuations carry a premium over those with more. In this respect, they’re like the odometers on cars. There are several ways to check the number of camera shutter actuations. Still, they vary from brand to brand, so I recommend doing a web search about the model you’re considering. Since this only matters if the shutter works, it’s essential to do several checks.
Check whether changing the shutter speed actually changes the exposure. In Shutter Priority mode, take several photos across a range of shutter speeds, from one second to the camera’s fastest, which is typically 1/4000s or 1/8000s. Review the images to ensure that they’re evenly illuminated from top to bottom. The shutter is beginning to malfunction if the top or bottom of the frame starts to grow progressively darker at faster speeds.
When taking these photos, pay attention to whether there’s a noticeable delay between depressing the shutter button and the shutter firing. Some delays are caused by the autofocusing system, so set the lens to manual focus first.
If the camera is capable of continuous or burst mode, test to make sure it works. Set a reasonably fast shutter speed, point the camera at a static scene, and take a burst of photos. The photos should all be consistently exposed.
This advice comes from personal experience. I once dropped my DSLR, and the impact created a slight misalignment between the autofocus system and the focus points displayed in the viewfinder. Essentially, when I wanted to use a single focus point on a subject, the camera would focus the lens on the area halfway to the left adjacent focus point. It was a huge pain in the butt and costly to repair.
A mirrorless camera’s autofocus system is built into the image sensor. If the sensor works, the autofocus system can take readings. You want to test that it accurately communicates focus readings to the lens.
To test the autofocus system on either type of camera, compose a photo of a small, well-defined subject that stands out against the background. Using a single focusing point, autofocus on the left edge of the subject and take a photo. Take a second shot focusing on the subject’s right edge. You can repeat these steps on the top and bottom edges to be extra thorough. Just make sure to manually defocus the lens between every shot. After you’re done, review the photos on the screen to confirm whether the camera focused on the intended target.
Your choice of shooting mode determines which camera settings and controls you can access. Except for several retro-inspired and pro-level models, most cameras have a rotating dial for selecting shooting modes. You want to confirm that the physical dial and its electronic connections are working and correctly aligned with the indicated mode. In practice, this means selecting M puts the camera into Manual Mode, selecting A (or Av) puts the camera into Aperture Priority Mode, and so on. Ensure the detents are firm, and if the dial has a locking function, that it works.
Checking whether the rear screen works is straightforward: switch on the camera, push the Menu or Info buttons, and the screen should activate. To check for dead pixels, take one completely white (overexposed) photo and review it for black dots. To check for hot pixels, take a completely black (underexposed) photo—keeping the lens cap on helps—and review it for pixels that won’t turn off.
If the mirrorless camera you’re considering has an Electronic Viewfinder, check the frames you just captured in it as well, as EVFs can also have defective pixels.
If the LCD is a touchscreen, give it some pokes, swipes, and pinch-to-zooms to ensure accurate touch sensitivity.
If the camera you’re examining features a multidirectional screen, check the condition of its joints by moving it around and confirming that it stays in place.
Many new DSLRs have a feature known as Live View, which lets them work like mirrorless cameras by displaying a live image on the rear screen. They do this by raising the mirror and opening the shutter so the light from the lens can fall directly onto the image sensor for as long as Live View is active. It’s typically activated by a dedicated button.
Activating video mode on a DSLR will also throw it into Live View, showing the view on the rear LCD. Regardless of your camera type, you can test video mode by recording a video and reviewing the result.
This is about checking the physical integrity of the controls themselves, not the underlying features associated with them. If rotating a dial, pushing a button, or moving a switch causes the camera to respond, it’s reasonable to conclude it works. Just make sure the buttons have adequate resistance and the dials maintain their detents.
The pitfall in this assumption is reassigned custom function buttons. To ensure that you don’t confuse the seller’s customization for malfunctioning buttons, remember to ask them to reset the camera to factory defaults before you meet.
As a rule of thumb, an opened pop-up flash always fires when taking a picture. The only exception is the “No Flash” Auto shooting mode on some entry-level cameras. The simplest way to fire a pop-up flash is by raising it, setting the camera into Manual shooting mode, and taking a picture.
And while I’m on the subject of flash, some advanced and professional camera models feature IR or wireless triggering of remote flash heads. If this function is vital to you, consider this your reminder to test it.
The humble tripod mount is found on the bottom of virtually every digital camera. However, it’s often overlooked during inspections because of its ubiquity and relative sturdiness. You can perform a quick visual inspection of the tripod mount to confirm no cross-threading damage. Still, I recommend bringing a tripod mounting plate or 1/4” ‑20 screw for physical confirmation.
A similarly overlooked physical feature of most cameras is the strap connector. I should emphasize that I’m not referring to the strap itself or the loosely attached strap rings or triangles. The strap connectors are the metal eyelets permanently attached to the sides of the camera body. These unremarkable parts are indispensable for your camera’s convenient and safe use. Make sure they’re not bent, cracked, or detaching.
In addition to checking it for dust or lint, the viewfinder assembly also contains light measuring sensors that determine auto exposure and assist in manual exposure. To check whether the light meter is working, select any auto shooting modes and point the camera at different parts of the scene. You should see a change in the shutter speed and aperture values as your view sweeps across the scene, which indicates that the meter is working.
You’ve probably already confirmed that the internal display works when taking test shots and checking for defective pixels. Now it’s time for a more thorough check for internal dust, moisture, and scratches on the eye-facing lens.
Additionally, make sure the IR proximity sensor activates the EVF when you move your eye towards it, and turns it off when you lower the camera.
The diopter adjuster allows you to set the viewfinder to match your eyesight. It’s typically a wheel or switch located somewhere near the viewfinder. To check that it works, or whether it’s strong enough to correct for your eyesight, look through the finder with your unaided eye and adjust the diopter control until the viewfinder indicators come into sharp relief.
Alternatively, on a mirrorless camera, you can adjust the diopter while looking navigating the camera’s menu or reviewing an existing photo within the EVF.
Check whether the rubber eyecup is included and inspect its condition. It’s typically made from soft rubber that can wear with time or start to separate from the underlying plastic frame. Your goal is to ensure that the camera you’re inspecting fits the advertised description. If the camera wasn’t described as “like new,” don’t nitpick the eyecup since it’s easy to replace.
Most camera manuals list all the accessories included in the box. Go over the list to ensure you’re getting everything advertised by the seller. And if the battery charger is included, ensure that it works.
Now you should know what to check for when buying a used DSLR or mirrorless camera in person. If you have requests for topics, let me know in the comments, and I’ll consider them for future articles.
In this post, I’ll show you what to look for when inspecting a used lens that you’re buying in person. The following is a transcript of the video linked above.
New photographers who are passionate about their hobby quickly develop an enthusiasm for lenses and the creative possibilities they open. This desire often leads them to the secondhand market, which offers a cost-effective way to buy photographic equipment.
Unfortunately, when buying a pre-owned lens directly from a seller met through online classifieds such as Craigslist, Facebook Marketplace, and Kijiji, you’re giving up the peace of mind offered by store refunds and manufacturer warranties in exchange for a lower price. Such trades involve items sold as-is using cash-only (or cash-like) transactions. The nature of these deals means it’s your responsibility to confirm that the seller’s description of the item is accurate because if you discover a problem after the sale is complete, you almost certainly have no recourse.
Fortunately, you can protect yourself against a bad trade and confirm that a lens is in good working order by performing a thorough inspection of the lens on the spot. The following is a detailed list of what you should do and check when buying a used lens is person.
Although I recognize that this point is obvious, it bears mentioning: Remember to bring the camera for which you’re buying the lens, and don’t forget the battery and memory card.
This point deserves a short story. A few years ago, I was selling my Canon 85 mm lens and arranged to meet with a young woman at a Starbucks near my home. She was about fifteen minutes late and, crucially, had forgotten to bring her camera. Her realization quickly turned into embarrassment, which threw her off balance. She performed the most rudimentary inspection—confirming that the front and rear glass elements weren’t broken—gave me her cash, and quickly left. I’m honest, so she got a good lens; however, she could’ve easily been ripped off because she didn’t bring a camera to confirm that the lens was functional.
Unless you’re buying a rare collectible that’s spent its entire existence in a protective case or a lens advertised as “like new,” most camera lenses will have developed some wear and tear from regular use. Your goal is to establish that the used lens you’re inspecting matches the advertisement. Significant differences from the advertised description and images of the lens serve as a convenient warning that the seller is not entirely trustworthy.
In most cases, the pre-owned lens will match its advertised description, and you can continue with your examination. Wear and tear are inevitable on lenses that see use, especially by professional photographers. For example, it’s normal to find scuff marks and wear of the paint on the filter ring because it’s the front-most part of the lens. The ridges on rubberized zoom and focusing rings wear down with years of use. Hairline scratches and scuff marks on the painted or plastic exterior are also expected and largely unavoidable. Such superficial wear is normal and won’t impact the optical performance and characteristics of the lens.
Dents on the barrel of the lens deserve greater scrutiny because they suggest a more forceful impact or drop. Such force could easily knock the precision optics out of alignment and reduce optical performance. Ask the seller about the nature of the damage, keep it in mind, and continue.
Remove the lens caps to check the front and rear glass elements. Clean glass is easier to check, so if you find fingerprints, smudges, or dust on the glass, ask the owner to clean them off before proceeding with the inspection.
Examine the front and rear glass elements. Observe how reflections pass along the surface of the lenses. Ideally, the glass should be smooth and free from scratches, abrasions, or thinning of the anti-reflective coating.
In practice, tiny scuffs and hairline scratches, especially to the coating, won’t affect image quality in any measurable way. The only downside to buying a lens with scratched glass is that it may affect your future resale value. Additionally, if such a scratch wasn’t part of the seller’s description of the lens, you could use it to your advantage by suggesting a reduced price.
(For those of you wondering how badly damaged a lens must be before its evident in the photos, take a look at the following picture. Try to imagine what sort of damage caused this degree of softness and loss of contrast. Is it a scratch, or several? Is it a crack, or several? Now take a look at the lens that took the photo. How did you do? As it turns out, it takes significant damage to the front of a lens for the effect of that damage to be readily apparent in practical photography.)
With the lens caps removed, shine your phone’s LED light through the back of the lens while looking at its internal components through the front. Avoid looking directly at the magnified LED, as it’s incredibly bright.
If you’re in a dimly lit environment, you’ll see the concentrated beam form through the lens elements. You’ll also see a heap of dust and tiny imperfection that will make you regret ever trying this technique. Lenses get dusty, and zoom lenses get dustier. That’s because every time you zoom a lens, glass has to move back and forth, expanding or collapsing the interior volume. This motion displaces air, either pushing it out or sucking it into the lens. (On some cameras, you can feel air “blowing back” into your eye through the viewfinder.)
Fortunately, the dust found inside lenses is meaningless to photographers because it’s too small to matter and doesn’t resolve in your pictures. You want to look for fungus, which can show as soft fluffy dots or fuzzy fibres or webs sprinkled throughout the interior glass. Fungus spores find their way into a lens on dust and proliferate after extended periods of storage in warm and humid environments. The fungus can grow and permanently damage the glass of your lens unless it’s professionally cleaned. Always store your lenses in cool and dry environments.
The electronic contact points found on the back of modern lenses facilitate communication with the camera. Ensure that the contacts are clean and don’t exhibit signs of corrosion. The presence of dirt and other deposits on the electronic contacts of a lens can wear down the thin gold-plating and cause data communication errors, which can result in loss of aperture control, autofocus, optical image stabilization, and lens-related metadata. You can clean dirty pins, but corroded ones require repair.
A lens is attached to a camera using the mount, which provides a secure point of attachment and ensures that the lens and camera are correctly aligned. The vast majority of modern lenses have metal mounting rings, but a few budget-oriented lenses feature plastic mounts.
When you’re examining a lens with a metal mount, visually confirm that there’s no deformation of the metal tabs at the base of the lens. This kind of damage could prevent the lens from securely attaching to the camera, or worse, damage the camera’s mounting ring if forced. Additionally, check to ensure the lens mount is firmly attached to the lens barrel—the attachment screws shouldn’t loose or missing.
Plastic mounts are less likely to deform but more likely to crack, chip, or wear down. Examine the plastic mount and tabs for signs of cracks, and confirm the mount is firmly attached to the lens barrel.
Now it’s time to attach the lens to your camera.
Attach the lens to the camera body and make sure it locks into place with an audible click. The lens should fit relatively tightly, although a tiny amount of rotational give is normal. With that said, there shouldn’t be any tilting or sagging; the lens axis must always remain perpendicular to the image sensor.
Inspecting the focusing ring requires some understanding of what you’re buying. To help you, I’ll cover the three main categories.
Many vintage and some third-party or special-purpose lenses are focused by manually rotating the mechanically coupled focusing ring. Since there’s no autofocus fallback, it’s essential to confirm that the focusing ring works correctly and focuses the lens. With the camera switched on and your eye to the viewfinder, rotate the focusing ring from one extreme to the other. The scene in the viewfinder should shift in and out of focus. Additionally, the focusing ring should rotate smoothly across its entire range of motion without any grit or sense of slack.
The majority of autofocus lenses designed for SLR cameras feature focusing rings that are mechanically-coupled to the optical system. These types of lenses often have a focus mode switch on the lens barrel that let’s you select between manual focus and autofocus shooting. In most cases, the focusing ring will always work regardless of the focus mode. (Keep in mind, there are some exceptions to this, so know what you’re buying!)
Switch the camera on, turn the focus mode to Manual Focus (MF), look through the viewfinder, and rotate the focusing ring from one extreme to the other. Then, repeat those with the focus mode turned to Autofocus (AF). In either case, the scene should shift in and out of focus and the focusing ring should move smoothly across its range of motion.
There’s a small but growing class of autofocus lenses with electronically coupled focusing rings. These types of lenses are informally called “focus by wire” because there’s no direct mechanical connection between the focusing ring and the internal lens elements. Instead, your inputs are transmitted electronically to the motors driving the focusing system.
Turn the camera on, set the focus mode to Manual Focus, look through the viewfinder, and rotate the focusing ring. Since there’s no physical connection, you’re mostly confirming the electronic connection is intact, that the motors work, and that the focusing ring rotates smoothly across its range of motion.
Unfortunately, autofocus errors can occur on both DSLR and mirrorless cameras—even on brand new lenses. For example, the zoom lens I use to make these videos is my second copy. The first one had an autofocus so faulty that every two out of five shots were misfocused. I was lucky to notice the problem before my 14-day return period ended. Sadly, there’s no return policy when buying a used lens from someone you meet on Craigslist. So don’t be shy about carrying out a thorough inspection when buying an item that’s sold “as-is.”
To confirm that the electronic focusing system works and the lens can autofocus accurately, set your camera to use a single autofocus point and take several pictures of near and far objects, changing between them with every shot. Review each picture at full magnification to verify that the autofocus was consistently accurate.
Pro-tip: you can shift between photos while reviewing them at full magnification by rotating the main command dial on your camera.
The majority of zoom lenses have mechanically coupled zoom rings. Switch on your camera, look through the viewfinder, and rotate the zoom ring from one extreme to the other and confirm that your angle of view changes. The zoom ring should rotate smoothly with an even amount of resistance throughout the range of motion. You shouldn’t sense any underlying grit, impingement, or slack.
Since some zoom lenses extend outwards at longer focal lengths, it’s a good idea to inspect the newly exposed part of the barrel for abrasions, damage, and debris. Generally speaking, there shouldn’t be much give or wobbling, even at its maximum extension. However, some lenses can slowly extend when pointing down or slowly retract when pointing up.
When inspecting an electronic lens, it’s necessary to confirm that the lens can successfully communicate with the camera. In a sense, you’ve already confirmed this by engaging the autofocus. However, since there are some manual focus lenses with electronically controlled apertures, it’s a good idea to be specific.
You can confirm that a camera recognized an electronic lens when it displays an aperture value other than 0. As another option, you can take a picture and look at its metadata. When everything works correctly, the camera should display the zoom range, set focal length, and set aperture value in the picture’s metadata.
It’s important to make sure the aperture changes in size when adjusting the aperture value. Don’t assume that putting the camera into Aperture Priority mode, rotating a dial, and watching the f‑numbers change corresponds to a functioning iris diaphragm. Regardless of the f‑number you set, a modern lens will keep its aperture fully open up to the point that you push the shutter button to take a picture. The aperture’s size is adjusted to your chosen f‑number only when you push the shutter button. This behaviour facilitates more accurate autofocusing in darker environments and provides a brighter view in the finder.
The following method should work for both DSLR and mirrorless cameras, even those without a depth of field preview button. Put the camera into Manual Exposure mode, select a large f‑number and a slow shutter speed (something like 2 to 4 seconds), look into the lens from the front, and press the shutter down to take a picture. Take note of the aperture’s size during exposure, and then take several pictures more. The iris should close down to the same size consistently. Any deviation in aperture size without a corresponding change to the f‑number could spell trouble for the consistency of your exposures.
If you’re checking a used lens that features optical image stabilization, verify whether it operates by turning the switch on and off while looking through the viewfinder and half-pressing the shutter button. And if you happen to be inspecting a variable focal length lens, make sure you’re fully zoomed in, because the stabilizing effect is more obvious at longer focal lengths.
You can also place the camera into Shutter Priority Mode, select a relatively slow shutter speed, and take several handheld photos with the stabilization featured enabled and then several with it disabled.
When functioning correctly, image stabilization should reduce or eliminate the motion blur associated with a shaky camera.
And now it’s time for the bonus round of quick tips.
Many vintage lenses have mechanically-coupled aperture rings. When checking such lenses, ensure the aperture opens and closes all the way and consistently, and make sure the detents indicating intermediate steps are clicking.
If you discover that the lens comes with a UV or “protection” filter already attached, ask the seller to remove it. Removing the filter accomplishes two things: it gives you a better look at the condition of the lens underneath, and it demonstrates that the filter threading isn’t damaged. Imperceptible dents can damage the threading and make it practically impossible to remove or attach a filter.
If the lens features “weather resistance”—often designated by the characters WR—check the condition of the rubber flange around the lens mount for cracks, tears, or notches. This type of damage will essentially nullify the weather-resistance of both your lens and camera.
If the lens has a focus distance window—which is a clear plastic window with focus distance markings underneath—make sure that turning the focusing ring or using the camera’s autofocus moves the underlying display.
Lastly, it’s tremendously important to understand what you’re seeking to buy. Before meeting with anyone, read reviews of the lens you’re considering so that you can tell the difference between normal quirks and flaws or faults. Such basic research could inform you, for example, that the focusing system of the Fujifilm 90 mm ƒ/2 lens can wobble about when there’s no power to the lens—and that it’s a completely normal.
Conclusion
Now you should know what to check for when buying a used lens in person. If you have requests for topics, let me know in the comments, and I’ll consider them for future videos. In the meantime, you can learn more about photography by joining on of Exposure Therapy’s group photography lessons.
Hi there, my name is Paul, and this is Exposure Therapy. In this video, I’ll explain the reason for the inverse numerical relationship between f‑numbers and the aperture. This relationship is a widespread point of confusion for many beginner photographers, who regard it as irrational or needlessly complex. My goal is to dispel the mystery around f‑numbers and demonstrate why they’re a perfectly reasonable method for expressing how the aperture affects exposure.
Understanding the relationship between picture brightness and both the shutter speed and ISO is straightforward for students learning the basics of photography. Shutter speed is expressed numerically in time units, with the most common being fractions of a second; longer durations result in brighter pictures, and shorter durations result in darker pictures. ISO is also expressed numerically; bigger numbers produce brighter photos, and smaller numbers make darker photos.
In both cases, the relationship between the setting and its effect on picture brightness is easy to understand because there’s a positive correlation, and they move in tandem. For example, when you double the exposure duration, it doubles the brightness; when you halve the ISO, it halves the brightness. It’s a simple relationship that students in my photography workshops grasp with ease.
Unfortunately, the relationship between f‑numbers, aperture size, and picture brightness is not as immediately intuitive. Beginners are confused by the negative (or inverse) relationship between f‑numbers and aperture size. In addition, they have a hard time understanding why bigger f‑numbers represent smaller apertures that reduce brightness, and smaller f‑numbers define larger apertures that increase brightness.
The best way to address this is by starting with the basics. Inside every interchangeable lens is a ring of overlapping blades collectively known as an iris diaphragm or iris. Expanding or contracting the blades adjusts the opening in the centre of the iris, called the aperture.
When you hold a lens up and look at the aperture, what you’re seeing is technically called the “entrance pupil.” The entrance pupil is the optical image of the physical aperture as seen through the front of the lens. This distinction matters because when you look at the front of a lens, you see the aperture through multiple layers of glass that affect its magnification and perceived location in space compared to the physical opening in the iris. For the sake of simplicity, I’ll use “aperture” when referring to both the setting and the physical opening and “entrance pupil” in reference to dimensions.
Changing the size of the aperture adjusts the intensity of light passing through the lens. Increasing the aperture’s size allows more light to pass through the lens, increasing exposure and creating a brighter picture. Conversely, decreasing the aperture’s size reduces how much light passes through the lens, reducing exposure and resulting in a darker photo.
We express aperture values using f‑numbers and not as the measured size of the entrance pupil, such as its diameter, radius, or area, because it neglects the essential role of focal length. This can be demonstrated with a thought exercise.
Let’s pretend we have two lenses attached to identical cameras: one lens is 50 mm and the other is 100 mm, and both have entrance pupils with 25 mm diameters. Since their entrance pupils are identical in size, an equal amount of light enters each lens. However, because the focal length of the 100 mm lens is twice that of the 50 mm lens, the light passing through it has to travel twice the distance to reach its camera’s image sensor, which produces a darker image.
Reduction in brightness occurs because light has the property of spreading out as it recedes from its source, and from the perspective of your camera’s image sensor, this source is the point inside the lens from which focal length is measured. This trait of light to diffuse outwards is described by the Inverse Square Law, which states that intensity is inversely proportional to the square of the distance. In this example, the inverse square law informs us that the 100 mm lens exposes its camera’s image sensor to 1/4 the light compared to the 50 mm lens because it’s twice as long. This occurs because one over two squared equals one-quarter.
The 100 mm lens can provide an exposure equal to its 50 mm counterpart by opening its aperture to collect four times more light, assuming its aperture can open that much. Since apertures are roughly circular, we can determine how big they should be by calculating the area of a circle. An entrance pupil with a 25 mm diameter has an area of about 491 mm^2. The 100 mm lens would need an entrance pupil with an area of 1,964 mm^2, which is formed by a circle with a 50 mm diameter. Simple, right?
Fortunately, photographers don’t need to perform such calculations to take pictures! That’s because hidden within these numbers is a straightforward relationship. For example, notice how the exposure produced by the 50 mm lens with a 25 mm entrance pupil is identical to the 100 mm lens with a 50 mm entrance pupil. This is because in both cases, the ratio of the focal length to the entrance pupil diameter is 2:1.
This is precisely why the f‑number is sometimes called the f‑ratio. The f‑number expresses a ratio of the lens focal length to the diameter of the entrance pupil, and it’s defined by the equation N=ƒ/D. Thus, the f‑number equals the focal length divided by the entrance pupil diameter. It can also be modified to solve for the entrance pupil diameter using the equation D=ƒ/N. Thus, the entrance pupil diameter equals the focal length divided by the f‑number.
These equations demonstrate that choosing the same f‑number on a lens of any focal length will result in the same amount of light passing through the lens. They also explain the inverse relationship between f‑numbers and exposure. For a given focal length, as the aperture’s size increases, the ratio decreases, and vice versa.
A 50 mm lens set to ƒ/4 will have an entrance pupil diameter of 12.5 mm—because 50 divided by 12.5 equals 4. A 24 mm lens set to ƒ/8 will have an entrance pupil diameter of 3 mm. Some lenses can open to ƒ1.0, in which case the entrance pupil diameter and focal length are equal.
The standard f‑number scale is: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, and so on. The difference in exposure between adjacent numbers is one stop, which means that it either doubles or halves the amount of light passing through the lens depending on whether you’re opening or closing the aperture. However, the numeric sequence grows by a factor of about 1.4 or shrinks by a factor of about 0.7.
Most photographers simply commit the standard f‑number scale to memory. However, if you’re having trouble, a more straightforward method is to remember just the first two numbers—1 and 1.4—because the rest of the scale is an iteration of doubling each in alternating order. The next f‑number is always double the previous one. So the number after ƒ/1.4 is double of ƒ/1, which is ƒ2. Likewise, the number after ƒ/2 is double of ƒ/1.4, which is ƒ/2.8. And on and on it goes.
Lastly, doubling the f‑number, such as changing it from ƒ/2.8 to ƒ/5.6, reduces picture brightness by one-quarter. And conversely, halving the f‑number, such as adjusting from ƒ/8 to ƒ/4, increases picture brightness four times.
I hope this helped you understand the inverse numerical relationship between f‑numbers and their effect on the aperture. If you have requests for future topics, let me know in the comments, and I’ll address them in future videos. In the meantime, you can learn more about photography on ExposureTherapy.ca. See you next time.
One of the most discussed and misunderstood properties of portrait lenses is focal length. If you ask your preferred online community for portrait lens suggestions, chances are, many users will respond by recommending specific focal lengths.
Perhaps the most commonly recommended focal length for portraiture on full-frame cameras is 85 mm; other popular focal lengths include 50 mm, 105 mm, 135 mm, and 70–200 mm zooms. If you’re at all familiar with the concept of focal length, you should notice that most of these suggestions are in the short to medium telephoto range.
When explaining their recommendations, photographers claim that wide-angle lenses make faces look bad or that such-and-such focal length is too wide for portraits. When this sentiment is left as-is, the unfortunate implication is that some inherent and mysterious quality of wide-angle lenses causes ugliness and that longer focal lengths provide the solution. To help you understand these warnings and suggestions, I’ll briefly explain the concepts of scale and perspective distortion.
In my Composition for Beginners video, I touched upon the concept of scale, which I use to describe the apparent size of your subject within the photographic frame. Your subject’s scale is determined by two factors when you’re taking a picture: focal length and perspective.
The focal length of a lens determines its magnifying power. This is the apparent size of your subject as projected onto the focal plane where your image sensor resides. A longer focal length corresponds to greater magnification and a larger rendition of your subject, and a shorter focal length results in less magnification and a smaller rendition of your subject.
The apparent size of a subject at a fixed distance from the camera is directly proportional to the lens’s focal length. So, for example, if you photograph a kid holding a beachball and then switch to a lens that is twice the focal length of the first, the rendered size of every element in your image, from the kid to the beachball, will be doubled in size along their linear dimensions—meaning in height and width. That’s how focal length affects scale.
In photography, perspective is your camera’s point of view and is determined exclusively by the position from which a photo is taken. For simplicity, consider this the camera-to-subject distance. Changes in the subject’s distance have an obvious effect on their perceived scale in a photograph. Ask your subject to come half as close, and they’ll appear twice as large; ask them to move twice as far back, and they’ll appear half as small. That’s how perspective affects scale.
To maintain an equal subject scale in the frame, the focal length and subject distance must change linearly, together and in the same direction. If your subject doubles their distance for a given scale, you will have to double your focal length to maintain the original scale; if your subject halves their distance, you’ll have to halve your focal length. For example, if you like the scale of your subject at 50 mm, but circumstances force the photo to be taken from half the initial distance, you’ll need to use 25 mm to obtain the original scale. Unfortunately, shortening the subject distance can result in perspective distortion.
In photography, perspective distortion is an inevitable consequence of how subject distance affects scale. Objects that are close to the camera appear much bigger relative to objects that are farther away. So, for example, Ginger looks three times larger than Violet because Violet is three times farther from the camera. This relationship will hold whether their distances from the camera are 1 and 3 m, 5 and 15 m, or 20 and 60 m, respectively, because in each case, Violet is three times farther than Ginger.
This relationship stops being true when the camera starts to change its distance for the subjects whose distances are fixed relative to one another. The disparity in their apparent size will decrease as the camera moves further back until these differences become imperceptible. This effect is known as “telephoto compression”; however, despite its name, it occurs in photos taken with all focal lengths when a distant subject is visible. Telephoto lenses make it more obvious because the “tele-compressed” subjects are shown at a larger scale in the frame.
Ginger and Violet’s relationship plays out on a smaller scale within the features of a single subject. People aren’t flat, and we’re not cardboard cutouts; our faces, heads, and bodies have depth and dimension. In a standard portrait, your subject’s nose is closer to the camera than their eyes, which, in turn, are closer than their ears. These differences are relatively insignificant at long working distances. However, they become significant at the very close subject distances required to achieve a “standard” portrait composition using a wide-angle lens. This leads to perspective distortion, characterized by a nose that looks too large relative to the face, a narrower head, and ears that appear pinned back. From extremely close distances, the cheeks can occlude the ears altogether.
The characteristics attributed to perspective distortion are entirely a consequence of the camera-to-subject distance. The focal length of a lens doesn’t directly influence perspective. This bears repeating: focal length does not affect perspective. Despite this, it’s often blamed for the effect because different focal lengths are used for different purposes and varying subject distances. Wide-angle lenses are typically used from shorter distances, lest the subject appears too small in the picture, while long focal lengths are generally used from farther away, lest the subject appears too large.
Let’s dive a bit deeper. You’ve probably seen this or similar effects before. Here’s a famous variation, known as a “dolly zoom,” from the movie Jaws. This effect is created by taking your first shot from a close distance and using a short focal length. Take the second shot from slightly farther back and with a proportionately longer focal length. And on and on. Such animations commonly illustrate how different focal lengths affect our perception of apparent facial geometry. Most examples, such as this one by Dan V., label each frame’s focal length but omit the subject distance, which is arguably more important since you can’t have perspective distortion without changing your perspective. Since focal length doesn’t affect perspective, we can illustrate the same effect by varying the camera-to-subject distance without adjusting the focal length. Initially, the distortion is difficult to see because the subject becomes smaller. However, the perspective distortion becomes obvious when cropping each photo to equalize the subject’s scale throughout the sequence. Adding distance labels instead of focal lengths creates a much more practical point of reference.
When someone suggests that a particular focal length is ideal for portraiture, they’re really expressing two preferences: one for the relative appearance of facial proportions from a given distance and another for the subject’s scale within a composition. Only you can determine whether you share the same preferences for both.
Although there’s no ideal universal distance for portrait photography, we can find several clues in proxemics, which is the study of how people unconsciously structure the space between themselves and others. For example, consider the idea of interpersonal distance zones proposed by Edward T. Hall in 1966. These are divided into the intimate distance (from 0–45 cm), personal distance (from 45 cm to 1.2 m), social distance (from 1.2 to 3.7 m), and public distance (from 3.7 m and greater). Although these specific ranges are biased towards white American males and may not apply to you or your culture, you likely have an approximate notion of what you consider comfortable interpersonal distances.
Understanding this makes choosing the right focal length for portrait photography straightforward. First, decide the approximate distance from which you feel people look their best, and second, select a focal length that produces the composition you want at your preferred distance. Therefore, if you prefer how people appear from longer distances and favour tightly framed photos that border on head-n-shoulders, your style calls for a medium or longer telephoto lens. Photographers who are partial to environmental portraiture, which showcases people in their usual environment, can combine a long subject distance with a wide-angle lens. The permutations are practically endless, so do what makes you happy.
Keep in mind: if you discover a fondness for wide-angle close-scale portraits, it’s important to know the ultimate purpose and audience for your photos. Researchers photographed subjects simultaneously from two camera distances, 45 cm and 135 cm, in an experiment about the effect of perspective distortion on social judgment. Experimenters found that study participants preferred faces photographed from outside of the personal distance zone more than those photographed from within it and rated them higher for attractiveness, competence, and trustworthiness. When you get an opportunity to photograph your favourite evil politician, take a note from Platon: get close and shoot wide.
Jokes aside, this research was published in 2012, and mobile social media platforms have had years of explosive growth ever since. That means arms-length portraits—otherwise known as selfies—of celebrities, public figures, and your secret crush are ubiquitous and accessible and provide the general public with constant exposure to examples of perspective distortion on conventionally attractive faces, which is something we weren’t privy to more than a decade ago.
One more thing: telephoto lenses have a unique benefit over wide-angle lenses because their relatively narrower angle of view allows minute shifts in perspective to alter the photo’s background dramatically. It’s useful for removing parts of the background from the composition that you feel are distracting. Since short focal length lenses capture a wider angle of view, equally small movements will not accomplish the same goal.
And there you have it, a guide for choosing your next portrait lens. Personally, my favourite lens for portraiture is the Fujinon 56 mm ƒ/1.2. It offers an angle of view equivalent to an 85 mm lens on full-frame cameras—so it’s a short telephoto lens—features a huge ƒ/1.2 aperture at which it’s quite sharp, and has lovely bokeh. With that in mind, I’ve used this lens for many other subjects, ranging from still-life, street scenes, and landscapes. This brings me to my final point: no matter what lens you buy, no matter what category of photography it’s marketed towards, I encourage you to experiment using it on different subjects and in a variety of settings. Always explore and discover, and don’t put yourself in a box.
If you have requests for future topics, let me know in the comments, and I’ll address them in future videos. In the meantime, you can learn more about photography on ExposureTherapy.ca. See you next time.
In photography, a portrait is loosely defined as a representation of a person whose face and expression form an integral part of the image. While the predominant subjects of portraits are people, they may also feature animals, such as pets. Personally, I’ve taken many portraits of my pets.
Many beginner photographers incorrectly assume that portraits are limited to scales that depict a person from just above their head to their chest or shoulders. Although the visual scale of a portrait is loosely defined, we can set several basic limits. For example, although the eyes are important for facial identity and expression, they occupy a relatively small part of the face. Therefore, an extreme closeup of one eye is not a portrait. Conversely, an extreme long-shot—being a photo where some combination of great distance or angle-of-view renders the subject in small relief against their surroundings—is also not a portrait because the face and expression are lost in their surroundings. Any scale of representation that lies between extreme closeups and extreme long-shots can be a portrait and lends creative flexibility to your expression.
What is a portrait lens? You can capture a portrait with any photographic lens. However, this doesn’t mean every lens is a portrait lens. Traditionally, portrait lenses have several properties that make them more suitable for that role than other lenses.
One of these properties is a relatively fast (that is, large) maximum aperture. This would mean an aperture of ƒ/2.8 or greater for a zoom lens and an aperture of ƒ/2.0 or greater for a fixed-focal-length lens. (And keep in mind: lower f‑numbers represent larger apertures.)
The aperture serves two purposes. First, it affects exposure by limiting how much light can pass through the lens. And second, it affects the depth of field, which describes the degree to which areas that lie outside the plane of focus appear acceptably sharp.
Photographers exploit the depth of field to achieve effects such as deep or shallow focus. We use a large depth of field to attain acceptable sharpness in the fore‑, middle‑, and background of the picture. Conversely, selective focus photography features a narrow or small depth of field characterized by a sharply focused subject and a blurry background and foreground.
Lenses with large maximum apertures—represented by small f‑numbers and called “fast” lenses—give portrait photographers the option to capture photos with a shallower depth of field than slower lenses can obtain. Portrait photographers often use a shallow depth of field because it creates a striking visual separation between the subject and their surroundings. It’s beneficial in candid situations, which differ from studios or other controlled locations because the background is either impossible or impractical to change to your liking. Your only option for minimizing background distractions becomes rendering them out of focus.
Another desirable property of portrait lenses is high image quality. This is a fairly complex subject that warrants several dedicated videos, but I’ll briefly touch upon two important components for portraiture: good sharpness and pleasing bokeh.
Sharpness describes the ability of a lens to resolve fine detail of a subject that’s in focus. In practice, it’s characterized by the fine details and edges in the scene being rendered as fine details and edges in the photograph. When everything is focused, a sharp lens renders distinct details across the frame. In contrast, a lesser lens may produce images with a loss of sharpness towards the corners, where details may appear smeared, blurred, or split into their constituent colours, as if by a prism. Such loss of sharpness is caused by the presence of optical aberrations, to which no lens is immune.
Most modern lenses can easily produce sharp photos that show crisp edges and defined details across the frame when their apertures are set to the range of ƒ/5.6–11. However, portrait photographers often take photos close to their lens’s largest aperture to achieve focus separation between the subject and background. This presents a challenge for lens makers because the aperture’s size strongly impacts image sharpness. Optical aberrations are most pronounced when a lens is set to its largest aperture, and aberrations decrease as the aperture is stopped down.
While no lens is immune to sharpness-degrading aberrations, and every photographic lens has more aberrations at larger apertures than smaller apertures, smart engineering, superior glass, and precision assembly of your lens will have a measurable impact on its overall sharpness, including at its largest aperture setting. A high-quality lens that produces sharp images, even at large apertures, allows you to achieve a shallow depth of field and precisely render the subtle details of your subject’s face, especially in the eyes and eyelashes.
Another important trait of a good portrait lens is how well it can render blurry parts. Photographers use the term “bokeh” to describe the visual and aesthetic characteristics of the out-of-focus areas in photos. Beginner photographers are often surprised to discover that all lenses aren’t created equal in terms of the objective and subjective attributes of their defocus blurring.
Bokeh can exhibit various objective qualities that are influenced by the optical design of a lens. Bokeh can be round, oval, or polygonal—in which case it’s taking on the shape of the lens’s aperture diaphragm. Swirly bokeh appears to swirl or rotate about the optical centre of a lens. Catadioptric lenses—commonly called mirror lenses—create very distinct donut- or ring-shaped bokeh, which are especially visible in out-of-focus highlights. Lenses with aspherical glass elements render bokeh that looks like the concentric rings of an onion.
Bokeh can also feature various subjective qualities that photographers often describe using words such as “smooth” and “creamy” when describing pleasing qualities or “nervous” and “busy” to describe undesirable qualities. A hideous and distractive type of defocus blurring is called “Nisen” or double-line bokeh.
Applying this information towards your next portrait lens purchase takes a little research. Every photo retailer makes it trivial to filter their lens inventory by maximum aperture, and even if they didn’t, that number forms part of the name of virtually every lens you can buy. Searching for a particular lens’s image quality takes a little bit more effort, and you’ll have to refer to the wealth of lens and camera review websites vying for your eyeballs. My personal favourite site for concise lens reviews is OpticalLimits.com.
Choosing an appropriate focal length for your next portrait lens is where matters become incredibly subjective, and I’ll be covering that in the second part of this two-part series.
Hi everyone, my name is Paul, this is Exposure Therapy, and in this video, I’ll demonstrate how Adobe Lightroom Classic can help you select your next prime lens.
Most of the students that attend my photography workshops bring gear purchased as part of a bundle or kit marketed towards beginners. The kits typically include a basic DSLR or mirrorless camera, and a zoom lens with an 18–55 or 16–50 mm focal length, which varies depending on the camera make. Some kits include a 75–300 mm lens for greater reach, but these are rarer.
When the workshops transition to the topic of the aperture and depth of field, some students realize that their basic zoom lenses can’t achieve the shallow depth of field aesthetic they desire. This is followed by requests for me to recommend a large-aperture prime lens, which inevitably leads to a discussion about how to choose a useful focal length. And so I ask probing questions about their preferred subject matter, style, working distance, budget, etc., all in an attempt to glean the ideal focal length for each student.
This line of inquiry is common, but it’s also problematic because it assumes beginners can provide accurate answers to questions and concepts they’ve likely never carefully considered up to this point.
Is there a better way? There is, but I’ll need access to your computer.
If you take every picture a photographer has shot on a zoom lens and sort the results by the focal lengths used, you’ll find an uneven distribution of images among them: some will have a greater share of the total number of pictures than others. Barring a few exceptions, I propose that the focal length with the greatest share of the total—the plurality—is the ideal focal length for that photographer’s next prime lens.
Your camera embeds information about itself into every photo it saves. This is known as metadata. Examples of this info include the time and date of capture, the camera’s make and model, and, crucially, the set focal length of a zoom lens. This is true for virtually every modern DSLR, mirrorless, and point-and-shoot camera.
Adobe Lightroom Classic—emphasis on the Classic, as this can’t be done in their simplified version—has a function that lets you filter your entire entire catalogue, or a selection of photos, by a variety of metadata attributes, including by set focal length. When you activate the focal length attribute, the application displays a list of every focal length you’ve used to take the selected images, along with the total number of photos shot using those focal lengths. My theory is that focal lengths with a comparatively larger share of photos are evidence of a preference and can serve as a great starting point for picking your next no-regrets prime lens.
Now I’ll demonstrate the process.
[Demonstration in video]
The first and most obvious limitation of this method is that it requires Adobe Lightroom Classic. The so-called modernized version of Adobe Lightroom, the one available on both desktop and mobile platforms, can’t filter metadata by lens type or focal length. (On a side note: I firmly recommend Lightroom Classic over Lightroom not-classic.) I’ve also confirmed that both Apple Photos and Google Photos don’t allow filtering pictures by set focal length, despite their ability to read and display the data in question. I can’t comment about performing this type of analysis using other apps, such as Capture One Pro, Photo Mechanic, etc., simply because I neither own nor use them. So sorry.
Secondly, it’s important to understand that both the upper and lower limits of your zoom’s focal length range can own a greater share of the distribution. This isn’t necessarily because you prefer these focal lengths, but more so because they’re the hard limit of the lens. For example, if my lens tops out at 55 mm, but I want a bigger rendition of my subject, I’m going to settle on 55 mm despite wanting more.
Lastly, this analysis is limited to the focal length range of your existing zoom lenses. However, since the point of this method is to guide you towards a preferred focal length from among those that you use, this limitation is largely moot. I firmly believe that it’s more practical for beginners to expand their collection of zoom lenses before committing to fixed-focal length prime lenses. The ultimate point of this exercise is to engage in due diligence and photographic introspection so that you can avoid buyer’s remorse.
And there you have it, an easy way to use Adobe Lightroom Classic to help you choose your next prime lens based on the focal lengths you use most often. If you have requests for future topics, let me know in the comments, and I’ll address them in future videos. In the meantime, you can learn more about photography on ExposureTherapy.ca. See you next time.