The Ansel Adams Fallacy: "True perspective depends only on the camera-to-subject distance"

No.

Absolutely no by the maths of pure image geometry alone. When rendering 3D scenes on a camera sensor foreshortening is a function of distance alone and is completely independent of focal length. the object at 10x the distance will show far more foreshortening.

Your opening argument in the OP (your bold):

I will say this one more time, but I feel confident that you will still fail to grasp the meaning.

We do not see pure geometrical/mathematical perspective through human eyes.

So, what is the pure geometrical and mathematically correct appearance of a distant object?

Foreshortened

How that is rendered by pure geometry and correct maths onto a 2D plane?

Foreshortened

How is that 2D image rendered by pure geometry and correct maths to the back of the retina?

Exact copy of the original.

What we see when we view the image with a human eye?

Highly dependent on viewing position but generally accepted that we will normally see a distortion of the perspective.

Conclusion?

There is only one possible conclusion; we do not see the pure geometrical or correct mathematical perspective when we view images because if we did we would always see the same consistent foreshortened. The absolute truth is that the human visual system never sees pure geometrical or mathematically correct perspective

So it then becomes painfully obvious that you can't look at images and relate what you see to the pure geometry of image formation. If you did you would end up scrabbling around and making ever more nonsensical statements that contradict yourself, observation and pure geometry while still trying to bang that square peg in a round hole.

We see telephoto compression in images because we see those objects out of the context of their normal distance. We then make errors of judgement and misinterpret their perspective. The mathematically correct pure geometric perspective remains both constant and correct in an image, there is no misinterpretation in geometry, only in viewing. So you can't discuss it without including human perception.

This is getting so bizarre! All of the above must be plainly obvious??

Objects A and B are flat objects. All of object A is at the same distance from the camera. So there is no foreshortening as it is of zero depth already.

If you want to consider an object in 3D, then take object A to be its front face and object B to be its rear surface (with nothing visible in between in this very simple example). The foreshortening is then equivalent to the change in distance between A and B in the two photo situations.

You can take a more realistic object if you like, but then every visible point on the object will need to be moved to one tenth the distance for photo 2.

I have never said that we do. Perspective is a mathematical model to explain how the shapes and sizes of objects change when we project a 3D scene to a 2D image and then when the 2D image is viewed from a specified point (relative to the image).

I say "viewed" but that does not necessarily mean through human eyes. You could instead take a photo of it (from the specified point) or use machine vision to view it and interpret it.

Human vision is not an essential part of perspective. The same theory of perspective applies when photographs are analysed by machine.

What do you mean by "out of the context of their normal distance"? What errors of judgement are you referring to? Can you give a simple example, please?

So...

Involving 2D objects which will display no compression either geometrically or perceptually?

But:

And that includes your latest example, the relative sizes are not preserved in human vision, it's called size constancy scaling.

And:

So the effect of telephoto compression doesn't exist in the maths...

It's still not registering.

Is it just me?

No, I don't think I could make it simple enough to make any difference. There is enough information in this thread already.

There is nothing wrong with Ansel Adams' theory.

I'll stand by what I have said already. I think time will be the ultimate judge of who is right. Or perhaps we are both wrong. It seems unlikely that we are both right!

Ah, but I'm not the one trying to describe an effect that doesn't exist in pure geometry and only exists when we view images, entirely by the pure geometry that we don't see and the complete exclusion of human perception.

Besides, time was ticking before the start of the conversation and is pretty far along the road to being a judge already. But probably not so much on photo tutorial websites!

😀

The table will be approaching that look at a long enough distance - where the 'telephoto compression' becomes apparent.

Looks similar to an Isometric projection whereby the edges of the table are the same size as their opposites, i.e. no perspective involved.

en.wikipedia.org/wiki/Isometric_projection

upload.wikimedia.org/wikipedia/commons/9/93/Comparison_of_graphical_projections.svg

Let's go through this in detail.

If you view those thumbnails from 1m away, it is totally obvious that the 135mm shot shows compression relative to the 24mm shot (i.e. the background looks closer in the 135mm shot).

However, at that viewing distance it does not show compression relative to reality (i.e. to what you would see if you were standing at the camera position when the shot was taken). If you took your laptop to where the photographer stood when she took that shot and you viewed the thumbnails at 1m distance, with the actual Washington State Capitol Building visible across the lake at the same time, then it would be obvious to you that the Capitol Building looks further away in the 135mm thumbnail than it does in reality (when viewed from the camera position when the shot was taken).

When viewed from further away than the centre of perspective, distances appear extended, when viewed from closer than the centre of perspective, distances appear compressed (in comparison to what was seen from the camera position).

Try it sometime, it is instructive to do it for yourself.

You can even check it out with the photo displayed on your phone.

Yes, let's, in detail...

If you view each shot at a point relative to the centre of perspective the distortion disappears and the view is similar to what you actually see in front of you.

But all 4 images in that example were taken from different camera positions keeping the subject at the same variable size. So there are two variables, camera distance an viewing distance.

Now there is no distance at which you can view the image taken with the 24mm lens and it will look similar to the image taken with the 135mm lens. So the difference shown in the linked photos can't be attributed to the viewing distance of the photo and must be a function of camera distance.

Ansel Adams was correct? This is exactly what he was talking about.

@JACS This is the interesting part. The wide angle distortion as seen (at least partly) in the 24mm shot is the absolute fact of correct mathematical geometry forming an image from that camera position.

So why does that distortion disappear when we view that image from the centre of perspective?

If pure geometry is the constant and we are using machines as per @TomAxford then it must work the other way around. The image should remain constant and of a fixed perspective whilst the perspective in the real world changes until we reach a spot where they are the same. This is the function of pure geometry and exactly how it works on a camera sensor.

So why does that distortion disappear when we view that image from the centre of perspective as seen with human eyes?

What would happen if we found that world of pure geometry a confusing place, where perspective did actually change as we walked between the spots and took the photos in the link and so learnt how to cancel it?

Well, the world would become a much more stable place and your relative understanding about the size scale and distances between the objects wouldn't change. Your understanding about the size of the subject, the building behind and the distance between the two would remain constant.

It would be interesting to try it sometime, see if it proved instructive. 😀

So what would happen if we viewed a photo?

Well, if human vision did compensate for the way pure geometry dictates that relative shape and scale must alter as we change position (like the differences between the linked photos which are machine proven to represent correct geometry), then you'd expect it to do the opposite when you presented it with a fixed geometry that didn't change as you moved. You'd expect it to create variations in the perspective but in reverse. So if pure geometry dictates that "wide angle distortion" was the mathematical fact of a close camera position and the above is true: You'd expect the same cancellation at a point relative to the position the photo was taken, and as that cancellation would be relative to close distance you''d expect it to lessen as you moved further away. So if "wide angle distortion" was a pure geometrical fact of a close camera position you'd expect it to be a perceptual effect of viewing from too far away. And that would reverse for "telephoto compression" which is the geometrical fact of moving the cmaera further away and the perceptual effect of moving closer to view the image.

It would be interesting to try it sometime, see if it proved instructive. 😀

Andrew, there is a fundamental error in your logic. Consider this section of your argument:

Everything there is correct except the conclusion stated in the final sentence (which I have put in italics). To be logically correct, the sentence shown in italics needs to be qualified as follows (changes in bold):

So the difference shown in the linked photos can't be attributed to the viewing distance alone and must be a function of camera distance as well.

It is not logically possible to conclude that the viewing distance plays no part. All that can be said is that the difference in the photos must be due to either the camera distance alone or a combination of camera distance and viewing distance.

That logical error invalidates the rest of your argument.

This logical error is possibly the same one that Ansel Adams made in reaching his fallacious conclusion. It has been repeated many, many times since.

Oh dear. So you pick a hole in one sentence and with it find an excuse to dismiss a whole opinion?

That's not good science.

The mathematical fact of pure image geometry is that the differences between the four 2D images linked to is entirely due to camera/viewer position and they must be rendered on the back of the retina as an exact copy.

Therefore the forming of a 3D understanding when viewing images and the apparent variation of perspective with viewing distance is down to human perception/cognitive function. It simply doesn't exist in the pure geometry.

So you can’t then explain it only in terms of pure geometry. You must also include the nature of human vision in that description. Why do you have such a problem with this? Your failure to see it is really causing some unsound logic and unsupportable conclusions.

In the four images linked above the geometry of the images with the relative sizes between the Capitol and the subject is fixed in the image by camera position alone. It is entirely a function of human perception that we misinterpret those separate perspectives when we view those images. But there is no distance you can view the 135mm shot and see the Capitol as being half the size relative to the subject, you simply misinterpret the depth of the building and the space in between.

If you were able to see the far distance you'd also notice that both mathematically and perceptually the distance between the camera positions makes very little difference. Even in pure perceptual terms the viewing distance only really changes our interpretation of what we assume to be closer objects, our understanding of the relationships of distant objects remains remarkably stable regardless of scale/viewing distance because in the real world this is precisely what happens.

As in the iphone image below there is no distance at which you can view it where the foreground will look like a distant object just a there is no distance you can view the background and it will have the perspective of a close object, even if you crop and isolate.

You only see "telephoto compression" when you view photos of distant objects and "wide angle distortion" only occurs when the camera to subject distance is short. This is not reversed with print viewing distance, you can stick your nose right against the print and the foreground will not foreshorten, and similarly as you back away from a close up shot of a distant object the compression reaches a point where it looks normal then it just stabilises the further you move away. [edited for clarity]

Ansel Adams is still correct.

On the contrary, it is good science. An opinion is worthless if it is based on an argument containing fundamental errors of logic.

Sorry, not all of us use facebook.

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The difference is clearly because the camera position has changed and not the viewing position of the print:

Really? I haven't dismissed your whole argument even though your opening statement clearly fails the simple test of observation:

Wide-angle perspective distortion is seen when the viewer views an image of an near object from further away than the centre of perspective. Telephoto compression is seen when the viewer views an image of an distant object from closer than the centre of perspective.

The two do not reverse with viewing position.

Not really, you do make some conceptual leaps in the right direction. There is some truth in what you say, but only partial truth. Some of it is flat out wrong, and it is because you have a massive blind spot demonstrated again in the reply to @JACS a few posts above.

I've tried again and again to show you with solid examples how the world of pure geometry differs from the one you see through human eyes. (and I'm sorry I must put this in bold, would've liked to use capitals as well such is my frustration that this simple point is still not sinking in) The simple fact that we do see different perspectives in the same fixed image is absolute proof that human vision differs from the world of pure geometry.

And yet you still keep doing this:

You insist we are talking only about the maths, that human vision doesn't enter into the equation, then "BOOM" - reality is what you see. And being reality it is of course subject to the rules of reality, i.e. pure geometry. You may think you're looking at the pure geometry in the real world and in images, but you still haven't sussed that you're doing it through human eyes, and so you randomly jump between one and the other as the same thing.

Eye and Brain - R L Gregory:

"When an artist employs strict geometrical perspective he does not draw what he sees-he represents his retinal image. As we know these are very different; for what is seen is affected by constancy scaling. A photograph, on the other hand, represents the retinal image but not how the scene appears... ...The camera gives true geometrical perspective; but because we do not see the world as it is projected on the retina, or in the camera, the photograph looks wrong."

[EDIT] Just to add that the above quote being true, that we never see the world as it appears in accordance with strict geometry, then it must logically follow that if we do stand in the same position as the camera and hold up a picture so to view it from the centre of perspective to achieve the same view then we absolutely can't be seeing the strict geometry in the image either. And if all other image viewing positions create a distortion...

You really need to consider the nature of human vision.

You keep repeating the same mistake. For each of the four images, the camera position changes. For each of the four images, the centre of perspective changes and hence the viewing position relative to the centre of perspective changes when all four images are viewed simultaneously.

It is irrational to claim that the change in viewing position relative to the centre of perspective has no effect and that the difference is solely because of the change in camera position.

You really need to do some experiments keeping the camera at the same place and just changing the viewing position (relative to the centre of perspective), but you seem unwilling to do that. It would quickly expose the fallacy in your argument.

It's also irrational to claim that changing the viewing position of the image changes the lighting angle in the scene. These are separate effects. Perspective is ONLY changed by changing camera position. Human perception of the image in relation to how the image is projected/displayed is a separate topic only peripherally related. Neither one controls the other.