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05 Jul 2022

Compression

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Term:
Description: In photography, when we refer to compression we are speaking of a phenomenon involving lenses and the distance from the subject to the background and the subject to the camera. Compression is the “compressing” of a scene - a phenomenon in which the background appears to be closer to a subject and larger in comparison than it actually is. This compressed effect is achieved with telephoto lenses. The longer the lens, the further back the photographer must step back from the subject to keep them the same size in the frame and the larger and closer the background will appear. Some really interesting images can be created this way, for example in which the moon looms larger-than-life over a subject.

Perspective defines the spatial relationships between objects in a photo in respect to the viewpoint. How we perceive a scene all depends on which lens we are looking through, which then allows us to dial in camera settings and choose composition accordingly. So, why is it that we reach for one zoom lens over another, or maybe one prime over a telephoto? Often it's perspective and compression or desired 'distortion'.

This animation lucidly illustrates the effects that certain lenses have, and what distortion they cause. This sparked an interesting discussion in the comments regarding which lenses photographers use for specific shots or compositions.

Combining our artistic abilities with our technical know-how, we reach into our bag of gear and pull out a lens that we think works best for the composition we are envisioning, but have you ever stopped to think about the qualities this lens is attributing to your image?

Perspective Distortion

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There are two types of distortion that may lead you to gravitate towards one lens over another: lens distortion and perspective distortion. These two concepts are often confused with each other because they both fluctuate based on distance. Perspective distortion deals with your close proximity to the subject. With anything in our field of vision, the closer it gets to our faces the larger it appears in relation to the objects behind it. The further you distance yourself the smaller objects will appear in relation to everything around them.

Lens Distortion & Lens Compression

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While perspective distortion can be manipulated based on your distance to the subject, your lens of choice can determine additional distortion/affect compression. Let's say you are using a 16-35mm f/2.8 (a popular and versatile choice) staying at a 16mm focal length. The image produced will naturally have distorted edges due to the wide angle, making objects appear wider when they are closer to the edge. While lens distortion is exaggerated on wider angles, it still exists at all focal lengths, just to a lesser degree. Meaning, just because you are using a 50mm prime doesn't necessarily mean you are getting away without distortion

Similar to the caveat listed at the bottom of side-view mirrors on vehicles, lens compression simply means that background elements can appear closer to the subject than they actually are. We gravitate towards certain lenses that give us greater compression, such as a telephoto lens like a 70-200mm, to emphasize the effect. But here is where perspective comes into play: Using a 24-70mm wide angle lens can work the exact same way as the telephoto, it just depends on the distance between the subject and the background.

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You can visualize this in the example images above: one taken on a Canon EF 17-40mm f/4L  and the other on a Canon EF 70-200mm f/2.8L IS II USM. In the top image, shot at a 17mm focal length, our distance to the model is very close, but the distance between the background and the model is further. In the bottom image, shot at 200mm, we had to move further back because of the telephoto lens and our distance to the model increased, however, the distance between the model and the background remained the same but looks vastly more compressed than the top image.

Choosing one lens over another should be a calculated process and not based simply on wide apertures or compression qualities. Focus on your desired perspective and choose the lens that fits your vision for the image. Knowledge of how your gear works is a step towards strengthening your art and creating a signature style. For an in-depth understanding of the basics of photography and lenses, check out Photography 101 in SLR Lounge Premium and stream a wide array of workshops to further your photography knowledge.

For more information on how certain lenses affect distortion, compression, and composition, check out the Canon Lens War Series on SLR Lounge, for a visual comparison of a variety of lenses from the 16mm up to 300mm.

Watch the Video/Read the Transcription Below

How the Lens Affects Composition | Transcription

In this video, we're going to take a few minutes to talk about how the lens affects composition.

Did you know that there are actually fat and skinny lenses? Why is it that people get that perception of certain lenses? Really, it's about perspective, yes and the field of view of your lens. Exactly. You mentioned one thing there, perspective, which is huge because there's actually two types of distortion that I wanted to talk about. One is lens distortion and one is perspective distortion. Oftentimes these two things are actually confused with one another. Now, perspective distortion has to do with how close you are to your subject. You’ll notice that, really, with anything in our field of vision, the closer it gets to our faces, the larger it appears. In relation to whatever’s behind it. In reality, my hand is not bigger than this entire house, but at this distance, it does appear to be. If we are close to her subjects, then you’re making subjects appear larger than they actually are. This is perspective distortion. The further away that we get, the smaller they appear in relation to everything around them. The closer we get, the larger they are.

What about lens distortion? Well, lens distortion has its own thing. Really a field-of-view of 16, which is a much wider lens, right, has its own distortion where it stretches out the edges. If you were to shoot a bunch of people and you put some on the edge, it might widen them. Exactly. Lens distortion typically it happens more so the wider the angle of the lens. You mentioned 16 mm. It will happen at 35mm. It will happen at 50mm even, but it just happens to a less extent. The lens is basically bending light around the edges. That’s where you notice the lens distortion the most. On a wide-angle lens, you’ll see lens distortion pretty much everywhere but the center of that lens. It wouldn’t be too flattering if I were to say pop on this wide angle 14 mm lens, and I shoot you from this distance.

What would be flattering then as a portrait lens? You probably want to use a zoom lens or something that’s fixed at, say, an 85, which is my favorite portrait lens. The 85mm or whatever variant you have. We’re using the 1.2 professionally, but for the entire workshop we use the 1.8, and it’s an incredible lens. It’s a perfect lens for portraiture. Yes, standing back a little bit further, zooming in, it will eliminate that lens distortion. Perspective distortion and lens distortion — those are the two things that we kind of have to combat. Now, we did a Canon Lens Wars Series by SLR Lounge. In that series, we actually took the exact same shot. Well, very similar shot, actually, where we basically took the same composition.

We shut it first at 16mm or I think it was 17mm to start with, and then we backed up to 24, 35, 50, 70, 100, 200, 300, shooting the same composition on each of these shots. What we did it for was actually to compare the lenses to one another. We want to seek visual differences in lenses, whether there was actually as big of quality differences as people would think between, say, a 50mm 1.8 versus the 1.4 versus the 1.2. Now, it was very interesting. We found out that really in reality when you look at these images there’s not as big of a difference between these lenses as you would think. In often cases, primes, even the mediocre primes like the $100 to $300, $400 primes, they outdid all the other cameras, or at least all the other lenses I should say.

A prime is a fixed focal length like a 50. You can’t zoom in or out. You literally have to step closer or farther from your subject. A zoom allows you to change that, so you don’t have to step closer to your subject. You just zoom in. Yeah, essentially with a zoom you get the convenience of having the extra...well, not having to move so much. You control your composition with your focal length. With a prime, like you say, you’re moving back and forth a lot. But then you get better low light. You get a better bokeh aesthetic. What we found out also was that in addition to comparing the lenses we were able to see the difference in distortion, in lens distortion, but also perspective distortion. It’s crazy to see, basically, when we take that shot up close at 17mm, our model looks all distorted, and each step back you can see the model kind of looked more and more normal. With every step back. The other thing that happens is that these telephoto lenses, they kind of emphasize something that we refer to as lens compression.

Here's the thing. Lens compression, we refer to basically as telephoto lenses as demonstrating or illustrating lens compression. Basically, what that is is the background elements appear closer to the subject than they actually are. Now, the interesting thing is that if you take a shot at 24mm and you take a shot at 200mm, and then you zoom into that 24mm shot, all the way so you have the same exact field of view as you did on that 200mm image, the compression's actually identical.

What would be the point of that? There's absolutely no point in that. We go to these lenses because they kind of further emphasize that effect, but what that effect really is is by standing back further is what's happening is we're changing that perspective distortion, so we stand back further. The distance between the subject and the background is relatively shorter, basically.

Now you're talking about photographer's perspective? Exactly. When we took that shot, and you could see it. When we took that shot as 17mm, the trunk and the background of the tree looks like it's actually like several feet behind the model. It looks like it's disappearing into the landscape because our distance to the model is very close. The model's distance to the background is further, and then as we start to back up, the distance of the model and the background didn't change, but our distance to that model did. The further we step back, the more it looks like the trunk is actually coming forward. Okay, to add on to what Pye just said about lens compression, I want you to remember this very simple tip. wide-angle lenses exaggerate distances. Telephoto lenses compress distances. Like Pye said, while we call this effect lens compression and while we use different lenses to achieve the look, the compression really has nothing to do with the lens. It has to do with the photographer's perspective. Now, when we talk about lens compression and the effect that we want, we just say that we want to compress the background with a certain lens. It's actually good to know that the compression isn't actually coming from the lens, but rather the distance between the photographer, the subject, and the background, and the lens is just there to help achieve that zoom and the composition that we want. Either way, the most important takeaway here again is that shooting close to the subject on a wide-angle lens will definitely exaggerate the distance between the subject and the background. Stepping back and using a longer telephoto lens will compress or pull forward that background, so it looks closer to the subject.

All right, so we covered lens compression. We've covered lens distortion and perspective distortion. Everything's been covered, so if you guys want more information, check out the Canon Lens War Series on SLR Lounge. You guys can see us compare all the different lenses from the 16 mm all the way up to 300 mm. Everything in that range, we compared lens against one another. We compared basically the 50mm 1.8 versus the 1.4 versus the 1.2 and compared that to, say, a 24-70 at 50 mm to show you the visual differences. It's a great visual comparison of all these different lenses.

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