Why is so much nonsense talked about telephoto compression?

If you do an online search for "telephoto compression", you find lots of tutorials/articles on the subject, almost all of which contain such nonsense as "lens compression is due to distance, not focal length", "it is the distance that directly compresses the scene, not the lens", "lens compression doesn't exist".

Almost none of them mention that telephoto compression is dependent on the distance at which the photograph is viewed, not on the distance of the subject from the camera. Yet it has been known since the days of large format glass-plate cameras that viewing distance is an important part of perspective. This knowledge seems to have been forgotten and somebody came up with a non-sensical explanation for telephoto compression which has been propagated throughout the internet!

It gets to the stage where the same nonsense is being repeated by so many people that almost everyone believes it without stopping to ask themselves if it makes sense.

I think this is an example of how the internet can be even better at propagating nonsense than it is at propagating sound reasoning and good science.

The only article I have found online that gives a correct explanation of why telephoto compression occurs is the Wikipedia article on perspective distortion. However, like many Wikipedia articles, it is a bit of a dog's breakfast and not to be recommended as a tutorial on telephoto compression.

See also my threads "What is Telephoto Compression" and
"The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance".

I think it’s older than the net, it was already in the books I had access to in the 1990’s. Power of repetition? And maybe because we only looked at small prints at arm’s length?

The implicit assumption is always that the photos are viewed in the same conditions: same display size, same viewing distance, same medium, same lighting, etc.. So, when talking about "telephoto compression", both the display size and viewing distance are presumed to be the same.

However, this presents a slight niggle: display size of what? The recorded photo or the portion of the scene the two photos have in common? I will argue that the latter is the "natural assumption". For example, if comparing a photo taken of a scene at, say, 50mm and 200mm, we are talking about displaying the portion of the scene the 50mm photo has in common with the 200mm photo at the same size, then viewing both from the same distance.

Under these circumstances, which, again, I maintain are understood to be the case unless otherwise specified, then, indeed, only a change in the position of the photographer will result in a change in perspective for given viewing conditions (well, one might argue that a change in the focal point may also result in a change of perspective, too).

We still do, most photos are viewed on a phone screen. Display sizes simply vary less than focal lengths and practically never in relationship with the lens used.

I think the reason is that the term “telephoto compression” is a concise term for a complex subject. I don’t like the term, but it sticks.

"Telephoto compression" is just an artifact due to our long lenses being too slow. With something like a 400/2.8 or 600/4, most of the background would be blurred, no compression!

One of your PAs carries a Bigma around for you ? 🙂

Nah, too slow.

I move forwards and backwards and adjust focal length accordingly to choose the foreground and background but you are saying only the viewer's distance has an effect? And that Wikipedia article confirms this? Okay, okay, but I just want to have fun so I will continue with my "nonsense" and you can move to the back of the room or press your eyeballs to the screen whenever you look at my photos. That's why I have never used film or darkrooms either. "Good science" is just boring to me.

If 'you' (=someone) ever tried to generate a correct panorama picture, then you should know about perspective and parallax. As soon as you move the 'no parallax point' of the lens, you get parallax i.e. a slightly different perspective. www.janrik.net/PanoPostings/NoParallaxPoint/TheoryOfTheNoParallaxPoint.pdf

An obstacle close to the camera obscures some other obstacle in the background of the scene and in the picture. This determines the perspective in the picture and will never change by viewing the picture later on.

If you take a picture from a large distance at point Pd you may often use a telephoto lens for this - then the perspective in the picture is determined by Pd and the angle of view is determined by the length (mm) of the tele lens.

Looking at the picture later on from different distances my produce some effects in your visual system (esp. your brain), but the perspective in the picture does not change of course.

Hi,

I recall a series of pics in a book. I think it was a Nikon published one.

Anyway, a shot with a wide angle of a garden. Successive shots at each prime lens focal length all the way up the lens series. At the far end was a lady standing and you really couldn't make her out in the first shot. And she was pretty much all you saw in the last one.

Demonstrated what really happens pretty well since the camera didn't move.

Anyone else recall this and also recall (unlike me) just where this was published?

Stan

Was it this article :

photographylife.com/what-is-lens-compression

Its necessary to scroll down a bit passed the bridge, pelicans & the goats nose.

I don't really understand the level of explanation Tom (the OP) is aiming for, or am I entirely sure whether what he means by the term "telephoto compression" is the same as I mean. This seems a common difficulty and makes his complaint seem overly harsh. As much confusion about anything is caused by the choice of language as it muddled concepts.

My view on the practical use of perspective effects for photography can be summed as: Increasing the focal length makes the background bigger. Moving closer to the foreground subject makes the subject bigger. This means you can control the relative sizes of the background and foreground by:

1. Changing focal length (to increase or reduce the size of the background)

2. Changing your distance to the foreground subject (to increase or reduce the size of the subject)

a) Want to make the dog look huge compared to the house? Use a wide angle lens to shrink the house, then walk right up to the dog. Result: huge dog, small house.

b) Want to make the dog insignificant and the house big? Use a tele lens to magnify the house and walk backwards to shrink the dog. Result tiny dog, big house.

Is much more explanation than that needed for practical photography use? I was completely baffled by Tom's talk about viewing distance. I've no idea how taking a couple of steps back from or towards a print will suddenly introduce the kind of effects I describe in a) and b). Just experimenting on a couple of prints I have on the wall. Changing viewing distance makes the prints smaller or bigger, no change to perspective.

This aspect of the discussion is a bit of a mystery to me. Happy to be educated but only if it magically changes those prints on my wall...

Hi,

No, that isn't it. It was in the late 70s or early 80s I saw the series I was referring to. Might have been a photography book or a magazine. But I think it was a book published by Nikon.

Stan

If you keep standing at the same place and only zoom or change lenses, the perspective doesn't change, nor does the compression. If you move your position, however, the perspective does change as does the compression.

(from fstoppers)

Now if you view these images from different viewing distances nothing changes, let alone the compression.

@Flashlight:

What do you see when you look through a telescope or binoculars? How would you describe the effect on what you see?

Compression is a relatively made up word in photography with regards to telephoto lenses. All that is happening here in your left photograph, is because you are so close to the subjects head with a wide, distortion is present. You have had to get this close, to get a similar size reproduction of his head as with the 800mm...When you photograph at 800mm and are standing a huge distance from him, there is no distortion to his features simply because you are far away. Our brain correct this - when we are very close to someone we don't see their face like on the left, but optically that is what occurs. There is no magic in a telephoto lens. It just allows the camera to be further away from the subject, then that subject incurs no distortion (if it's a well designed tele).

To me, compression is an artistic tool. If you ever saw a picture of, say, a chapel in front of mountains, which are in reality far away from the building, you know what the term means.

By the way, please stop to call other people's opinion "nonsense".