Portrait lenses and focal length
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.
Scale, focal length, and perspective
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.
Perspective distortion and telephoto compression
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.
Perspective in portraiture
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.
The subject distance is the only factor in perspective distortion
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.
How to choose the correct focal length for portrait photography
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.
A final note on wide-angle vs telephoto for portraiture
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.