How Lens Focal Lengths Will Affect Background Compression
When I decided to write about the “perfect” portrait lens, I really thought I had a grasp on what I was going to talk about. As a Canon shooter, I imagined that I would spend all the time talking about the sharpness of the Canon 135mm f/2.0, or the amazing bokeh of the Canon 85mm f/1.2L II.
But only a few days into working on this project did I realize how much we talk about models of lenses, but omit an understanding of lens optics themselves. Like many photographers, I have lost track of the time I have spent reading, and watching lens reviews. Then saving up money to buy a certain lens, but not asking the most important question, will this focal length help me in my photography.
And I am not alone in this problem. At Shooting the West, a photo workshop and symposium in Nevada, I spoke about and demonstrated different focal lengths for a room full of photographers. In this lecture, I found that many photographers, regardless of experience, really didn’t understand why they are reaching into their camera bag for one focal length over another. Selecting a lens just more than getting closer or further away from your subject, or how soft the bokeh of a lens can be.
So I am not going to waste your time with pixel peeping, or bokeh comparisons. I am going to introduce the concepts of lens focal length and how it relates to compression, distortion and why this should be the first thing you think about when reaching into the camera bag, or purchasing a lens.
The first thing I think about when selecting a lens is compression, or how much of the background I am going to see behind my subject. To test lens compression, in the case of portrait photography, I asked my good friend, and go to model, Travis Stewart to stand in the same place as I took several pictures of him. For each shot, I would change the focal length while keeping him composed in the same space of the frame.
I started with wider-angle lenses first and then moved up to more telephoto. While the 16mm, 24mm, and 35mm focal lengths are not thought of as portrait lenses, look at how much of the background is displayed at these ranges. Travis is still present in the frame, but if the portrait was also about the area or place the subject lived or worked in, these focal lengths really show off the location and the subject at the same time. Of course, there is distortion at these focal lengths, which we will get to later, but even at 24mm, the distortion is not so radical that you couldn’t live with it, or just make a better composition, say full length.
At 50mm and 70mm there is a very nice balance of showing off a large part of the landscape, but making Travis really stand out in the frame. Still good focal lengths to use when you need to showcase that background.
After 100mm two things start to happen, first, the compression of the background is so great, that we have lost the mountain range, and now we are just seeing the hills directly behind Travis. And at 135mm and 200mm not only do only see the hills, but also those hills have moved right behind Travis. As my focal length become more telephoto, it looks like those hills are just over Travis’ shoulder, when in fact they were at least a half a mile away, if not more.
Another thing to look at in these shots is image distortion. With the 16 and 24mm, we see serious distortion in Travis’ face. I took another set of images for more of a headshot composition, which really shows off this distortion. It is interesting that Travis’ nose does get larger because of the distortion while his body and face are narrower. As we get to 50 and 70mm that distortion starts to go away, and the nose is back to a normal size, and all those hours in the gym are showing off.
Most portrait photographers avoid wide-angle lenses when doing portraits, because of this very distortion, but as a fun test, I had Travis hold out his water bottle to show how distortion could aid you with certain subjects. At 16mm, the water bottle is huge, and is the subject of the photo, but when I took the exact same picture at 200mm, the water bottle is now much smaller and lacks punch. What if you are hired by a sports team or athletic apparel company, and they want a portrait of a pitcher or quarterback holding a ball out towards camera? Shooting the wrong focal length could put emphasis on the wrong subject. A wide, or at least wider-angle lens would make that ball larger and make it stand out from the subject. A telephoto lens would make the image more about the athlete holding the ball.
And of course, there is the relationship of the depth of field to focal lengths. Notice in all of these photos, as the focal range increases, the depth of field gets shallower. All of the shots were taken at f/10. I do want to point out how close Travis was to the camera, which has a significant impact on the depth of field as well. Even at 16mm, the background is out of focus because of the distance of subject to the camera.
While much of this information was not news to me, it was interesting to put a subject in one location and see how the focal lengths not only impacted distortion, and depth of field, but also the environment I am working in. Right now my go-to lenses for portrait work are 35mm and 100mm primes lenses for this very reason.
It is these concepts you need to think about when purchasing and using lenses. If you are working in a small studio, or your location is not great, then a telephoto lens will not only reduce distortion, and give you a shallow depth of field, but it will also compress that background, so less of it is present. But if your location is on the assembly line of a factory and your subject is the CEO, you probably want to find a focal range, like 35-70mm, that will both showcase your subject and their location.
Lens data charts are great, and comparing the bokeh of one lens to another makes for great information, but when it comes to your work, make sure you are telling your story in the right voice.