What is telephoto compression (perspective compression)? Tom Axford 2023

With CNC we control x and y axis for length and width, z axis is depth. So x and y is size of subject while z is depth = front to back.

We can also add a 5th axis ...... that would be like a 3D effect.

I can do an example with an image or images but it might get a bit confusing! That's using z as a floating point for z=depth=perspective. We can vary the z images in size vs depth. Yeah I know, clear as mud I guess. Makes sense here though.

Still clear as mud to me, I'm afraid.

Okay, the mud gets thinner

Turns out it's very, very simple and we control it.

The result is a very simple one for compression. Of course if we change all three with x y z, every angle, perspective, depth and compression changes. Now we could change the properties altogether and end up with just a flat photograph with no compression.

Simply we end up with .....

Ahhh, let's call that taken with a 300mm. So if we now use a 500mm the effect of z would pull that back image close and larger, x and y doesn't change. Then if we used an 800mm lens the same would happen again, closer and larger. But nothing actually changes except z = focal length.

Back to this one which most people didn't seem to get

That's with an 800mm tele. If it was taken with a 300mm the effect wouldn't be that much with the closeness of the gull. If it was taken with a 1200mm lens it would look even closer and larger with the seagull. That seagull landed I would say about 5 feet back from the Cormorant. It didn't even know it was there, but it looks like its about to land on the cormorant, so that's the z floating point depending on which focal length you use. I use it all the time but for different purposes. Exactly the same principle Tom.

So basically compression is what you make it.

Danny.

Edit: Yeah the top part is a bit confusing if you don't get g code, so took that out.

Interesting posting.

However, when I say that telephoto lenses compress the perspective, I am thinking of something different. I imagine photographing the same subject from different distances filling the frame. We all know that the background seems to get closer to the subject. That is compression for me.

You will argue that it is not the telephoto lens that produced that result, but the distance to the object. Okay, that is right. However, I want to teach to take the right lens to take an image of a subject. Taking the right distance is just an obvious consequence.

Yes, I agree that the background appears to get closer to the subject if you move the camera back but zoom in to keep the subject the same size.

But now consider the case when you zoom in without moving the camera back. In that case also, the background appears to get closer to the subject.

What conclusion do you draw? Is compression caused by moving the camera or by zooming the lens?

You cannot zoom in without backing. I am interested in photographing subjects. The subject you are photographing will change, and you see only part of it. How should I compare a wide-angle shot of a flower bed with a macro shot of a single flower in terms of background compression? Does not make sense to me, not even in architecture.

Haven't you ever taken a full length shot and then zoomed in for a head and shoulders shot or even a head shot? I am very surprised. Try it sometime.

You obviously try to misunderstand me, or I really did not express myself. Giving up.

I may well have misunderstood you, but it was not deliberate. Indeed, I was trying hard to understand what you wrote.

I am still unclear. Were you agreeing or disagreeing with what I said in the OP: that compression is caused by the eye seeing a magnified image (compared to viewing the original scene with the naked eye)?

In the case of a portrait where you keep the subject the same size in the frame, but change both the camera position and the focal length, then it is increasing the focal length that introduces compression (because it effectively magnifies the image); while changing the camera position changes the perspective seen by the camera, but does not contribute to the perception of compression.

Edit: Actually don't mind me, I'll just back out of this one 😀

You are right, the whole point of this thread is to explain what it is and why it occurs.

I assume that everyone has already seen it. There are millions of examples out there - just do an online search for "telephoto compression".

If you view your images normally, any focal length greater than normal (about 50mm FFe) will lead to you seeing a magnified image and the impression that distances from the camera (or viewer) are compressed. Of course, the effect is not very noticeable until the focal length is several times normal.

If you buy a pair of binoculars, you probably won't bother unless the magnification is at least 6x. In photographic terms that corresponds to 300mm FFe focal length.

Telephoto compression is defined as the illusion that everything in the scene is closer to the viewer than is the case in reality.
If you are using long lenses all the time, you will get very used to seeing it. That doesn't mean that it is no longer present.

The main reason that photographers use very long lenses is because they make things look closer than they are.
That's telephoto compression.
Nothing more.

If one person is 100m away and another person is 200m away, when you look at them through 10x binoculars (or photograph them with a 500mm FFe lens), the first person appears to be 10m away and the second person appears to be 20m away. The distance between the two people appears to have shrunk from 100m to 10m. That is why it is called compression.

The distance appears compressed. It's really very simple.

I think there is more to it that that.

Consider a line of five parking meters, each 10 feet apart. If you stand 10 feet from the nearest meter, and take a photo, the furthest meter is 50 feet away from you. That's five times as far away as the closest meter.

Now stand 100 feet from the closest parking meter, and use a telephoto lens to get the same framing as the first photo. Now the furthest meter is 140 feet from you. That's not even twice as far as the closest meter.

By standing further away the space between the parking meters appear to be "compressed". The distance to the furthest meter has gone from being five times as far as the closest meter, to not even twice as far. This makes the spacing between the parking meters appear to be less.

Go to a zoo where there's a 20' trench between the walkway and the lion. Have your friend stand on the walkway, with the lion 30 feet away. If you a photo while standing 5 feet from your friend, it will look like he's nowhere near the line. Stand 500' away, and use a telephoto lens, and it will look like he is close to the lion.

You have changed two things in going from the first image to the second image: (1) the distance from the camera to the closest parking meter; and (2) the focal length of the lens.

Lets separate those two and see what is causing what:

1. Take a photo with a 50mm lens from 10 feet away. When you view that photo normally, the meters will appear to be at their real distances from the camera, i.e. 10', 20', 30', 40' and 50'.

2. Keeping the same 50mm lens, move back to 100' from the nearest parking meter, and take a photo. Viewed normally, the parking meters will appear to be at their actual distances from the camera, i.e. 100', 110', 120', 130' and 140'.

3. Now, keeping the same camera position, take a photo using a 500mm lens. This effectively magnifies the central part of the second image ten times. This telephoto image, viewed normally, creates the impression that distances from the camera are compressed ten times. So the parking meters now appear to be at the following distances from the camera: 10', 11', 12', 13' and 14'.

The parking meters now appear to be only one foot apart, whereas they are really ten feet apart.

It is the use of the telephoto lens that causes the apparent compression, not the change in camera position.

It is worth noting that if instead, you make the second image using the 500mm lens, but from the same camera position as the first image, then it will show telephoto compression and everything will appear to be ten times closer than in reality. So the parking meters will appear to be at the following distances from the camera: 1', 2', 3', 4' and 5'. This image shows exactly the same compression as the third image. The parking meters appear to be only one foot apart, although the narrow field of view of the 500mm lens means that only a small part of each parking meter will be visible.

Of course, this image is very difficult to make. The very small depth of field of a 500mm lens at 10' subject distance means that the some of the parking meters will be badly out of focus in a single shot. It will require focus stacking to get a sharp image of all the parking meters. Also, an expensive cinematography lens will probably be needed to avoid focus breathing and ensure that the image magnification does not change when the focus is changed.

I disagree.

If you don't change camera position and switch to a telephoto, things will not appear "closer." It will simply appear as if you made a bigger print and cut out the middle.

The human optical system is quite sophisticated. It can tell the difference between a close shot with a normal lens, and a far shot with a telephoto lens. The difference is from the difference in subject distance.

Try the following test. Put the camera on a tripod and take two shots of the same scene. For the first, use a 200mm lens. For the second, use a 28mm lens and crop the resulting image to match the framing of the 200mm lens. You will find that the two images look the same. This demonstrates that the subject distance, not the focal length, is the important factor.

Here's another thing to try. Take a photo of a person and make two prints. One 4x5" and one 8x10". Show them to various people and ask them in which photo the subject was standing closer to the camera. Most people will correctly notice that the photos are the same, and the subject distance is the same. Making the subject bigger, does not necessarily make it appear closer.

I can agree with you on nearly all of that.

If you don't change camera position and switch to a telephoto, it will simply appear as if you made a bigger print and cut out the middle. I agree.

Put a camera on a tripod and take two shots of the same scene using a 200mm lens and then a 28mm lens and crop the latter image to match the framing of the 200mm lens. Both images look the same. I agree.

Take a photo of a person and make two prints. One 4x5" and one 8x10". Show them to various people and ask them in which photo the subject was standing closer to the camera. Most people will correctly notice that the photos are the same, and conclude that the subject distance must be the same. I agree.

However, I disagree with your conclusions. I think you have convinced yourself that telephoto compression does not exist and you interpret everything in those terms.

You don't think that looking through a telescope (or a pair of binoculars) makes things appear closer. If you are determined to maintain that position, then I am not going to waste time arguing with you. Almost everyone I know thinks that telescopes and binoculars do make things look closer.

Your point, with sample photographs, is incredibly useful for the beginner.

I personally like the term "zoom with your feet." Although it is not accurate (you are not really "zooming') the point is that by walking about, you consider the perspective of your composition and you give yourself more options than if you merely stand in one place and zoom the lens. Walking closer is not the same as zooming in.

Is that how people think when they take a photo? I don't think so.