Understanding Focal Lenth and Perspective

My rant from the other day had a few people confused. Not about my point, more about something that comes up a lot and has been explained countless times since the dawn of time. Unfortunately I make a lot of assumptions here about ”stuff everyone knows”. I assume people know a lot — bad idea considering how much ridiculous-ness is chucked out on the internet per second. I would love to kill about 350 birds with one stone but I’m depressed and lazy and really don’t feel like making pictures today so I’ll settle with a mere one bird for this with a slathering of other birds that could be killed but will escape for another day. How about we talk about perspective, field of view, distortion, focal length, and stuff of that ilk? Okay?

The shot at the top is something I made while still in my phase of seeing how much I could make a 35mm field of view look similar to something I shot with a 50mm. Answer was, pretty similar but that’s mostly because I am familiar with manipulating perspective and the way it looks. Here’s the rub — perspective and perspective distortion, and all that shit has nothing to do with your field of view or lens focal length.

Now before everyone goes apeshit and starts calling me an idiot just bear with me. That above statement is absolutely true, a fact. That’s not an opinion but an unalterable property of the universe we happen to live in. Perspective and perception of distortion of such only depends on how close you decide to get to your subject. Now all those people that held off on calling me names, field of view/focal length has a lot to do with how close you stand if and only if you want the same in camera framing. So there is the one and only relationship. Shoot a narrower field of view/longer focal length and you stand farther away than you would if framing the main subject the same with a wider field of view/shorter focal length.

Let’s look at StupidCrap™ exhibit A:

Shot with a 28mm lens. Here’s exhibit B shot with a 50mm from the same exact place:

It’s the exact same perspective of what we could consider my main subject, the Fuji X100S in the foreground. Don’t think so? Sure it is, the relationship between the size of the X100S and the Nikon F3 behind it are the exact same. If you think otherwise it’s all in your head. Maybe the shit that’s even closer to the camera is fooling you because you can’t see it in the 50mm shot.

I’ll help you out with exhibit C. The 28mm shot with a quick and dirty crop for the same/similar framing. Give me a break, my tripod is outside in the ice/snow/arctic in my car. Not going out there today.

So what’s this all mean? We’ll a couple of things first off is what makes perspective distortion. It’s how close you are standing or how not close. Usually when discussing the “distortion” what’s being discussed caused by wider and wider angles of view. In reality it really isn’t the wider and wider… it’s the closer and closer. There is the other kind of perspective distortion — the kind when you are farther and farther away… For some reason we don’t use “distortion” for this instead we use “compression”. Honestly both are “distortions” in terms of how “big” or little something appears in relation to other stuff in front of or behind it compared to our normal perception of things.

One and only bird dead… I hope. How about some other birds that I’ll not attempt to kill but at least give some of my own perspective on — even if somewhat distorted… Man, that was twisty-turny wasn’t it. I couldn’t resist.

There’s a notion out there that when shooting people one kind of distortion is good while the other one is bad. In my experience that rule of thumb isn’t the case at all. I think that mantra comes from an underlying assumption that the photographer will fuck it up no matter what focal length he/she chooses and no matter where they stand or how they position the subject relative to the camera and all the other stuff. In other words whoever is doing the shooting is going to take the worst possible picture of this theoretical human subject. If we make that assumption then maybe the worst possible picture you could take standing far away is less horrifying than the worst one you could take really, really close (assuming the same framing). Possibly but once you graduate from photographic kindergarten and stop optimizing for worst case I will absolutely assure you closer and wider allows manipulation of the relative size of a human’s anatomy that can be far more “attractive” than the reverse.

Obviously all of this has to be taken with some degree of thought process — I know, I know, that’s difficult since it’s ever more popular to want some one answer to all things on all occasions and to minimize any thought that will go into it. You’re going to be hard-pressed to do a tight headshot with an 18mm lens with someone’s face strait on to the camera. Let’s consider that a specialized case… really tight headshots with face head on to the camera. Let’s not go berserk and do something more reasonable okay?

How about full length/three-quarter/waist-up kind of stuff? In these contexts I would much rather use a 50mm than a tele, truth is I would even prefer a 35mm or a 28mm for most people. Why is this? because through smaller and smaller shifts of camera position and camera angle relative to subject I can manipulate the relationship how big/small body parts are to each other. Not for gross effects but for subtle adjustments to anatomy. In most cases to get a person’s shape to be more what I perceive it to be in real-life/being there/three dimensions. A tiny tweak to camera angle and reposition of the camera can subtly or drastically alter hip/waist ratios and all the rest. In most cases this can be a very good thing.

Just to exaggerate one tiny thing I’m talking about let’s take a crazy example. Say I’m doing a full length kind of shot. I frame it up on a 28mm. If I move the camera up or down just a few inches and adjust the tilt to frame the subject the same there will be a huge difference in the way a subject looks and point of view. A foot, two feet? Even bigger. If I frame up the same shot with say a 300mm lens it will look exactly the same no matter if I’m laying on the ground or standing on a box; If not exactly then really close.

Let’s go back to our tight headshot example for a second. I will tell you that even with very attractive people some people’s facial features look “better” a little more stretched out front to back vs more smashed together. That may not mean the difference of using a 14mm vs a 300mm but it certainly does when choosing a 50/85/105/135/200…

Now another bird, out of focus-ness. I wont’t spend too much time on this but I have to cover a really simple case so that I can answer about 3,000 questions regarding the rant… The closer you are to your subject the less DOF you are going to have at any given aperture, in fact a shit load less. Sooooo what does this mean and what does it have to do with the rant? If you take two similar lenses one farther away and one closer the one shot farther away then cropped will have more depth of field than the one shot closer. Hence my rand regarding say a 56mm f/1.2 Fuji having “breath-taking DOF” as if it’s somehow so much more breath-taking than a 50mm. No, in-fact it’s a lot less breath-taking if the definition is how out of focus your background is. Standing in the same place they’ll be the same. If however you move closer with the same framing the 50mm on the bigger sensor will be far far far more “breath-taking”, even at smaller apertures. Don’t believe this to be so? Okay maybe I can accidentally kill this bird with the shitty example’s above. A 28mm and a 50mm shot at the same f/4 aperture. Take a quick look at the “breath-taking-ness” of all those shots, like how out of focus/lack of DOF each displays.

As you would expect the 50mm exhibits a little less depth of field than the 28mm standing at the same place when cropped. Now what happens if we say frame the 28mm like the 50mm?

Well we certainly changed the size relationships didn’t we? In fact we have the “perspective distortion” we all talk about right. How about out-of-focus-ness??? Meh, I would say it’s a toss up now. About the same? Certainly close and trying to tell the difference is really thrown off by the change in size relationship for sure. Let’s agree no matter which one is “more” out of focus it’s not night day now. Think about this for a second. A 28mm has nearly TWICE the angle of view as a 50mm but has about the same DOF when you get closer… interesting right. What do you think happens when you use a a 50mm-ish from far away then crop it vs using a 50mm-ish 50% closer? Obviously the closer one will be way way, way, way more out of focus. Hence the rant that somehow a 56mm lens with a half-stop faster aperture used (typically) farther way has some magical out-of-focus property that didn’t exist prior to it to the extent of “breath-less”. Say I’m doing a waist up shot with the 56mm on an XT-1 or the same shot with any old 50mm on a full frame. Which one will be more “breath-taking” if measured by out-of-focus-ness? Ummm the 50 because it’s about the same focal length but a shitload closer.

Birds killed — hopefully one.

RB

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