Why is so much nonsense talked about telephoto compression?

In my question above I was specifically referring to the visible noise in the first sentence and you quoted it yourself.

Sorry I'm not interested in talking about my (or should I say, your) imaginary frustrations with you.

You are proving my point 😄

Let's see if you can stay on topic.

This is an example of the "nonsense" that I was referring to in the title of this thread.

The argument above is incorrect because it assumes that the perspective captured in an image is exactly the same as the perspective we see when we view that image.

In fact, the perspective we see when viewing an image depends on the position of the viewer relative to the image: both on the distance away (relative to the size of the image) and on the angle of view (relative to an axis through the centre of the image and perpendicular to the plane of the image).

When viewing a photograph (taken with a rectilinear lens), there is only one viewing position that gives exactly the correct perspective, other viewing positions give different perspectives which are distorted (often only slightly, but sometimes more obviously). By "correct" perspective, I mean the perspective seen from the camera position.

If the image is viewed from too far away, then wide-angle perspective distortion may be apparent.

If the image is viewed from too close, then narrow-angle perspective distortion (i.e. telephoto compression) may be apparent.

Whether or not distortion (of either type) is apparent depends very much on the subject matter of the image.

This diagram, from the Manual of Photography (7th edition, 1978) may help. It shows the viewing position needed to see the correct perspective, i.e. exactly the same perspective that the camera saw. For this to happen, the angle of view seen by the camera and the angle of view seen by the viewer must be the same.

Your so-called counter-examples are not counter examples at all. I have already explained them to you.

Tom, pardon my confusion but which parts of the "above": are nonsense/incorrect?

1. Saying "it's not zooming that creates the compression effect" is incorrect.

2. Saying that "someone talking again and again about the appearance of background objects being closer to the foreground objects is misleading" is incorrect. Compression means that background objects appear closer to the camera; foreground objects also appear closer to the camera; and background objects also appear closer to foreground objects. All appear closer by the same factor.

3. Cropping a zoomed out image is irrelevant. As I explained, it is magnifying the image (e.g. by zooming the lens; or by looking through a telescope; or by cropping and then enlarging the crop) that causes compression.

The issue is that the objects appear closer to each other without appearing closer to the camera, and it's still perceived as compression.

That's probably the main point of controversy here.
The compression effect is just perspective at a long enough physical distance where the ratio of angular sizes of objects converges to the ratio of their physical sizes. Again the compression can be seen without any zooming/magnification/cropping, maybe if I frame it like this it'll be clearer:

And yet again, compare the image above with another one, where zooming in from a different (closer) perspective doesn't show any compression:

I agree that picking the right viewing distance to the image can amplify the effect, generally classical paintings were designed to be viewed at a certain distance. With digital displays, phones and monitors, the best viewing distance is disregarded most of the time but we still see compression or the lack of it depending on the physical perspective, not the viewing distance.

That is the well-known "dolly zoom" effect. It is a combination of perspective distortion and change of camera position. In other words, the viewing perspective and the camera perspective are changed in such a way that the subject appears to remain at the same distance (the subject is kept the same size in the frame).

So, it is still compression, but done in coordination with changing the camera position. There is a very nice computer simulation of the effect shown in the Wikipedia article. Notice that on zooming in, the background gets closer to the subject while the foreground also gets closer to the subject. In other words, everything becomes compressed closer together.

Thanks, I missed the response.

With respect to #3:

If I shoot two images from the same location at two different focal lengths, all else being equal, and then crop the wider result to match the framing of the narrower result and then view them side-by-side, there will be a difference in the apparent relative distance of the same objects in each image?

There will be no difference in the apparent distances if both images are the same size. So you need to crop the wider image to match the framing of the narrower image, and then enlarge it to the same size as the narrower image.

Thanks, I'll have a play sometime ...

)Hi Gang! I am a new member of this site. I have always been a photographic enthusiast but my day job, for the last 50++ years is commercial and portrait photography. This job does not necessarily make me more talented or somehow superior to any other photographer but t gives me a different perspective on practicality and theory vs. practice. This is not gonna be off-topic s pleaseo bear with me.

Please don't misconstrue this to say that I am not into theory, science, optics, and all the technology and technobabble (it's fun) and I even went to school and studied all of that, enjoyed it, and for the most part, left most of it in the classroom. .

Of course, perspective control is an important part of serious image-making. It can be applied to create realistic accuracy of the subject, forced, to engender dynamic lines in composition and altering perspective can change the "statement" an image makes or the story it tells the viewer. There is no doubt that the "recipe" for perspective control is a mixed bag. The theologians of purist theory insist that perspective is only a function of distance. That works on "paper" or in a totally controlled situation, where the photographer can work at various distances and use various focal lengths until he or she finds the effect they like or is attempting to achieve. Out in the field, not so much. Oftentimes I am forced to work from a particular distance and have to employ a focal that will "get the shot".

I am quite familiar with viewing distance issues because some of my images will appear in a small brochure or magazine ad and some will end up on a billboard or the side of a bus- sometimes, I don't know which! I make a shot for a restaurant menu and the client likes it so much he decides to have me create a MURAL for his signage. So folksl will view it on a pamphlet and some folks will see if from across the street! Even in the tightly controlled situation in my portrait studio, I can't work at a distance based on "compression" or expansion of the background, my first consideration is not to distort the subject's face to foreshorten their body. If any of y'all has ever shot with a view camera with a tilting and swing back, that adds a whole new ball of wax to perspective control and forced perspectives.

A lot of this is common sense. A wedding couple is not going to view their wedding album from across the room or on the Jumbotron athe local sports arena. Most of the time a 30x40 executive or institutional portrait in a board boardroom or lobby will not be viewed from inches away, that is unless the viewer is a fussy photographer using a loupe, a microscope, or a telescope from a distance to examine the pixels!

You think this is bad, I just read a post where folks are dissecting the structure of circles of confusion in their "bokeh" and having an intense argument as to what "bokeh" is and how it is actually generated. If I was to chime in and simply say they are romantic little focus light bubbles, I would be verbally set upon and bludgeoned to death.

I have had the privilege and pleasure, over the years, to train many new photographers, kinda break them intothe trade, as it were, and these academic debates would often occur. I would just tell them story of the young couple and the newborn baby. Seems the baby was crying and screaming and would not fall asleep, keeping the mom and dad up all night. Grandma, who lived downstairs, was awaked and came to see if she could help. She found he baby crying in her crib and the rookie parents frantically turning the pages of their "Child and Babay Care" book. Grandma gently said, "Put down the book and pick up the baby"! Problem solved! So, stop arguing, pick up your camera and your lenses, and shot what shoot, not an experimental setup, and SEE what get. You can't move a building or a mountain as you can with a couple of test targets. You can't pose an athlete in midair or shoot from form the third baseline or behind the home-plate unless you are the Ump or the catcher with a bodycam, at a pro baseball game. You can' allways select your shooting distance due to obstructions, restrictions or lighting issues. You learn to work around, improvise and getting job done. The THEORY is great as long as you keep it in back of you mined. Obviously, you can't concentrate on on you subject and applly artfulness if you are bogged down with diagrams, instrumentation, calculators, slide-rules (old school), protractors, and and optical bench) and are too busy fumble with your gear to conform to some axiom. Just call me "GRANDPA"!

The crew here at the NEW DPR has done a yeoman's and heroic job of setting up this forum. I was hoping that the debates would not "go south" with grumpy or vitriolic arguments as that oftentimes spoil online photo forums.

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Was Ansel Adams perhaps responsible?

In Ansel Adams' book "The Camera" (published in 1980), he states (on page 106):

It seems that he may well have had a serious blind spot in his understanding of perspective and failed to realise the importance of viewpoint relative to the centre of perspective when viewing an image.

Adams was hugely influential through his books, magazine articles, workshops, etc. Could he have been partly responsible for the many thousands of photographers today with an inadequate understanding of what causes perspective compression (telephoto compression)?

I guess I don't see the problem with what he wrote. He quite correctly places perspective in the realm of the geometry of the scene. The lens just "crops" small parts of the scene, with the resulting effect on the viewer regarding the image.

Photographs captured with a long focal length provide a view humans have a hard time seeing in real-time, as we can't make our eyes crop a small part of the world around us. You can concentrate on a small part of the scene and see what the camera/lens captures, but you can't really obliterate the rest of the scene in your view.

I've heard the preference for 35mm versus 50mm expressed by others and, by coincidence, I have recently bought a 20mm CZJ Flektogon for my Sigma SD9 which makes it 34mm equivalent. I also preferred the 41mm equivalent view of my Sigma DP2 to the later 50mm eqiv. DP2M.

A quick test as I sit in my wheelchair reveals a horizontal field of view about 90 degs (1.6 rad) when looking fixedly ahead. For my SD9's 20.7mm-wide sensor, that would indicate an actual 33mm lens.

The anomaly now is that I view my monitor at about 1 radian horizontally implying that I still need an actusl 20mm lens or a much wider monitor.

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The oft-quoted 180+ degree AOV for human vision does not include an ability to identify objects at right and left.