The first step in becoming proficient at any of the manual exposure techniques discussed below is by familiarizing yourself with the quick and precise setting and adjustment of your camera’s shutter speed, aperture, and ISO values. The second step is learning to adjust your camera’s metering modes. The remainder of this guide will assume you’re comfortable with both. The third step is to remember everything you have learned about the aesthetic and technical aspects of the shutter, aperture, and ISO, and put that knowledge into practice. Lastly, it’s important to understand that both this and the following section are concerned with manual exposure, not manual focusing. Too often, students and other beginners gain the impression that manual mode requires manual everything, which contributes to their feelings of intimidation. Fortunately, they are incorrect; in fact, the only contemporary camera systems for which this is true is Leica’s M-series, which is incapable of automatic or semi-automatic focusing.
Is manual exposure necessary?
Memorable photographs, especially landscapes, are often the result of lighting conditions that are distinctly ‘not average.’ Under these unusual circumstances, normal rules and automation will probably fail to produce the fine, expressive photograph you have visualized.
–John P. Schaeffer
Manual exposure allows you to take control of your image. It encourages you to halt and apply a slower, more considered approach to your photography, freeing your mind from the shackles of thoughtless snapping at every opportunity. In a way, it fosters you to make creative decisions with a purpose.
Modern cameras provide for multiple ways to make the same exposure. Every day, many advanced and professional digital photographers rely on the auto-exposure smarts of their cameras to achieve quick and effective results. There are also situations in which manually setting the exposure is the only viable technique for acquiring the image you visualize. You’re encouraged to experiment with and discover the methods that suit your preferred style.
Ultimately, manual exposure isn’t necessary in most photographic situations. Nevertheless, understanding how it works, and how to use it to achieve desired results, will undoubtedly be helpful in cases that require it.
Sunny ƒ/16 rule of thumb
Every photographer should know the following rule of thumb: when your subject is in direct sunlight, set your exposure to ƒ/16 and a shutter speed that matches the reciprocal of your ISO value. For example, for a camera set to ISO 200, the correct exposure for a subject illuminated by direct afternoon sunlight on a clear day will be ƒ/16 and 1/200 second. When the situation calls for less depth of field and faster shutter speed, feel free to adjust the proportions according to the reciprocity law. An equal exposure at the same ISO speed will be obtained at ƒ/11 and 1/400 second, ƒ/8 and 1/800 second, and so forth.
Copy your auto-exposure values
In situations beyond direct sunlight, one of the most natural beginner techniques for experimenting with manual exposures that produce good results (most of the time) is by copying the auto-exposure settings. This involves taking several trial images using your preferred auto-exposure mode and analyzing the exposure values. If the results of a particular photograph strike your fancy, switch your camera into manual mode and replicate the shutter speed, aperture, and ISO.
Use a handheld incident-light meter
A more advanced technique, yet one that’s incredibly simple and accurate (especially for portraits or subjects within reach) is using an incident-light meter (see Metering Light). Contemporary light meters take measurements in either Aperture Priority or Shutter Priority modes. In either case, you set the ISO value and either the shutter speed or aperture (depending on the desired effect), and take a reading of the incident light from the position of the subject and with the lumisphere pointing in the direction of the camera. After taking a measurement, the light meter will display the correct exposure values for the image—the two inputs provided by you, and the third one determined by the meter based on a reading of the light.
For example, you want to take a portrait in open shade on a bright sunny day. You have decided that a narrow depth of field will be your priority because it provides a pleasant separation between your subject and the background; hence, you choose ƒ/2. And, because there’s plenty of light, you decide on ISO 200. (The ISO value may be adjusted if the meter specifies a shutter speed that you deem too slow.) With these intentions in mind, you input these values into the light meter. To take an accurate reading of the light falling on your subject, hold the light meter’s lumisphere directly in front of your subject’s face and point it straight towards the camera’s intended position. After measuring the light (which takes a split second), the meter will display the shutter speed necessary for achieving a correctly balanced exposure, which in this example is 1/1000 second. Adjust your camera’s shutter speed, aperture, and ISO to match the light meter’s exposure values and take the picture.
If you’re using an unusually large and complex lens, the light meter’s recommended exposure values may require a slight adjustment of +1/3 to +1/2 EV to compensate for the difference in your lens’s transmission value (see F-stops and T-stops in Aperture). If you have an older light meter that doesn’t allow input of exposure compensation, make the determination independently when setting your camera’s exposure values. For example, adding +1/3 EV to a shutter speed of 1/1000 second will produce a shutter speed of 1/800 second, and adding +1/2 EV will result in 1/750 second. Fortunately, newer electronic models allow users to set exposure compensation in the light meter, which is automatically factored into the displayed exposure values following a reading.
Use the camera’s reflected-light meter
The most accessible and readily available method for manually setting your camera’s exposure values relies upon its built-in reflected-light meter. With practice, the process is incredibly simple and takes just several seconds to complete; however, it depends on the complexity of the scenario and how nimble you are at manipulating your camera’s exposure values since the procedure can differ among different models. Before you begin:
- Familiarize yourself with how and where your camera’s viewfinder or LCD show exposure information. (The conventional order from left to right is shutter speed, aperture, and ISO.)
- Determine which of the available metering modes at your disposal bests suits the scenario (because the technique relies on their correct use). Alternatively, and for the sake of simplicity, select either called evaluative, matrix, or multi (depending on your camera’s brand).
Reiterating two points from earlier is essential. First, the large notch (or zero) at the centre of the light meter scale in your viewfinder always designates the standard exposure index, which marks the point on the scale that your camera considers optimal exposure. In this case, “optimal” is highly dependant on your metering mode. For instance, when your camera is set to evaluative metering, optimal is determined by the camera’s auto-exposure program based on a sophisticated analysis of the scene; in spot metering mode, optimal is the exposure value that will render the tone that overlaps with the spot as middle grey in the resulting image. Second, in Manual mode, the exposure level indicator shows how much your set exposure values deviate from the standard exposure index (i.e., the camera’s optimal). When the exposure level indicator is positioned directly below the standard exposure index, there’s no deviation from optimal exposure.
Lastly, it’s necessary to recognize that the exposure level indicator is dynamic and liable to wild fluctuations—shifting between indications of too much or too little exposure—depending on the part of the scene your camera is aimed. This behaviour is especially true when relying on spot metering mode to take your exposure readings.
The process of setting your exposure values manually using the on-camera exposure meter is straightforward whether you’re using a camera with an optical or electronic viewfinder, live view LCD, or rangefinder. In the interest of more precise instructions, the remainder of this guide will assume your camera uses an optical viewfinder, as is standard with every DSLR. Rest assured that the process is similar across most cameras.
After composing your image in the viewfinder, take a look at the exposure meter and pay close attention to where the exposure level indicator is compared to the standard exposure index. (For the purpose of this exercise, assume the standard exposure index always marks an objectively “correct” exposure.) Since every camera will maintain its manual exposure values between powering on and off, it’s unlikely that your settings will be correct for the subject at hand, especially if your last photo was taken at a different time of day or under different ambient light. If the indicator is on the positive side of the index, the camera’s meter is advising you that your current exposure values will produce over-exposure in the photo. If the indicator is on the negative side of the index, the camera’s meter is advising you that your current exposure values will produce under-exposure. If your camera’s exposure values fall outside the limits of the light meter’s display, either the indicator will flash, or triangular arrows will appear at the end of the scale corresponding to over- or under-exposure. In either of these three cases, adjust your exposure values (shutter speed and aperture) or ISO in a manner that brings the indicator needle to align with the index mark. “Correct” exposure is achieved when the indicator aligns with the index.
For example, if your camera is currently set to 1/80 second, ƒ/1.4, and ISO 1600, and the exposure level indicator is at +2 EV, the camera believes that your current exposure values and ISO will produce a photo that is over-exposed by two stops. To remedy this, adjust one of the three parameters by –2 EV. Alternatively, you may change two of the three settings by –1 EV, or all three by –2/3 EV. Regardless of how you reach a total compensation of –2 EV doesn’t matter (see Reciprocity Law). In this particular example, if your shutter speed and aperture suit your subject, then reduce the ISO by –2 EV to ISO 400 for lower image noise.
Of course, indiscriminately following the advice of the light meter in manual mode is no different than relying on it entirely in one of the auto-exposure modes. You should always use your better judgement as a photographer to understand the subject, the scene, and where the camera’s program may go astray. For example, if you’re taking a picture of a person dressed in very bright clothing against a bright background, adjusting your exposure values and ISO to align the indicator with the standard exposure index will produce an image whose tones are middle grey and not representative of the subject. As with exposure compensation, it’s often necessary to use your better judgement and stray from what the camera considers optimal exposure. In this example, a correct exposure would be achieved when your exposure values and ISO shift the exposure level indicator to show +1 EV to +1½ EV. Conversely, when taking a photo of a darkly dressed subject against a background of low-reflectance foliage, you’ll achieve a correct exposure when your exposure values and ISO place the exposure level indicator to –1/2 EV to –1 EV.
With adequate practice and frequent repetition, the operation of your camera’s exposure controls will become instinctive and guided by muscle memory. Get out there and practice.