Why is so much nonsense talked about telephoto compression?

In that wiki article, there's no references/proof that the absolute angular size is more important. On the contrary, it talks more about the relative angular sizes.

At least you acknowledged that the relative sizes are somewhat important, which is different from your original statement where you claimed that the compression doesn't depend on the physical distances at all:

Now about your earlier thread on telephoto compression - your examples are based on "shoot from a long distance, view at a close distance", so again the physical shooting distance directly affects the result.

But you claim that the viewing distance is everything, and I think you need a stronger evidence to support that claim.
At least I don't really see the compression effect fading away as I move an image away from my eyes. It could depend on the type of the scene and visual references in the image that help estimate the relative and actual sizes.

Also I find inconsistent your definition that the compression starts when the lens is > 43mm. How does it align with the claim that the compression depends on the viewing distance?

You are correct, both are important to our perception of depth in a 2-D image.

However, "compression" is caused by magnifying the image, which increases the absolute angular size of everything in the image, but does not change their relative sizes.

I am not saying that relative sizes are unimportant to depth perception, but simply that there is no change to the relative sizes when an image is magnified.

Take an example. Suppose I am looking at a person 100 metres away and another 200 metres away. The person seen at 100m has an angular height of about one degree, while the person 200m away has an angular height of about 0.5 degrees.

If I view the scene through 10x binoculars, the angular height of the first person becomes 10 degrees and the second person 5 degrees. My brain judges their distance away by absolute angular size and therefore thinks that the first person appears to be about 10m away and the second person about 20m away. The distance between them appears to have shrunk from 100m to 10m.

You get exactly the same effect by taking a photo with a 500mm lens and making a 5" x 7.5" print and viewing it from about 10" to 12" away.

Cropping and enlarging the crop gives exactly the same effect as using a longer focal length. Both give the same compression in our perception of depth in the image.

See also my reply to Quarkcharmed.

Now you are telling blatant lies because I never said that.

What I actually said is

dprevived.com/t/why-is-so-much-nonsense-talked-about-telephoto-compression/3111/post/42185/

Not in my images after cropping.

Your definition of "lens compression" is clearly different to what I use.

What I'm actually saying is that relative angular sizes are more important (they depend on the shooting distance).
Absolute sizes of familiar sizes of objects are also playing their part but there's other visual cues including relative sizes of objects.

Again take the same example (shot #2 that I posted above)

... and zoom in (by cropping)

I don't really see the effect of compression here. That's because the shooting distance was short enough to produce the corresponding perspective.

"lens compression is the appearance ... when you zoom in".
How is what I said a blatant lie?

Please post your cropping examples ":from a given position" ...

meanwhile, see 'What Lens Compression Isn't' for a cropping example:

photographylife.com/what-is-lens-compression

Certainly when the shots are taken "from a given position" - see above reference.

Do tell us how wrong Ansel Adams was and watch your credibility slump even more ...

Well, they are more important if you change the camera position. But if you keep the camera position the same, they don't change. Do you agree?

Yes, but if the camera position remains unchanged, relative sizes do not change.

You should see the effect of compression. If you don't, it's probably because your conscious brain is overriding your instinctive interpretation of the two images.

Try to imagine that you are looking at two different scenes. Imagine that they are not photographic images, but small windows that you are looking through at two different scenes. In the first, the nearest screwdriver has an angular size of about 7 degrees in my viewing conditions, and the second is about 3.5 degrees (very roughly), and they appear to me to be (very roughly) 3 feet away and 6 feet away.

In the second image, the angular sizes are about doubled, so the screwdrivers appear about 1.5 feet away and 3 feet away (very very roughly). So the distances appear compressed.

Of course, it is extremely difficult to estimate actual distances, we are not very good at doing that and even less good at doing it from photographs. Yet the brain is still pretty good a detecting differences in perspective and recognising that a telephoto image doesn't look entirely realistic (if the image contains enough objects that are familiar to us). Your screwdrivers pictures are not particularly good for demonstrating compression because we don't know what size those screwdrivers are, and that affects our judgement of distance.

Being able to estimate distance is a useful skill for a photographer. Most of us from the zone focusing era are pretty good at it. It can be learned, and carrying and using a laser rangefinder can help with that learning.

Yes, some people in the military used to be very good at estimating distances. I'm not sure if that is still the case today with laser rangefinders being so readily available.

Don't you see an issue here?

We can define and measure compression when we talk about relative sizes of objects in a photograph. The longer the shooting distance is, the closer are the ratios of apparent sizes to the ratios of physical sizes. At a distance, as we move the objects along the line of sight, their apparent sizes don't change as much as they do at a closer distance.
getThat's all measurable.

But when you talk about brain overriding instinctive interpretation, the effect of compression becomes much harder to define and measure because we're now talking about viewer's inner experiences.

Hmm... because of that, the screwdrivers are actually good for illustrating differences in individual perception.

Now another shot (which I also posted earlier)

The apparent sizes of the screwdrivers are now almost the same (and their physical sizes are the same) and we have some compression even without zooming in.

@Quarkcharmed:

I find it very difficult to have a rational discussion with you because you seem to be determined to not seriously consider the effect of magnification on perspective and depth perception. Please, let's forget all about relative distances because it is not relevant to compression. You seem determined to keep dragging it back into the discussion. It is not relevant to compression.

What matters is our judgement of absolute distance and that depends primarily on the angular size of a familiar object as seen by the human eye. If we see a person whose angular height is 4 degrees and they walk away from us until their angular height is 2 degrees, our visual system knows that they are about twice as far away.

If we look at something through a telescope that magnifies 6x, then the angular size of everything becomes six times larger when viewed through the telescope. Our brains interpret this to mean that everything is six times closer to us.

So, when we look through the telescope at a familiar scene, we do not think that we are looking at a scene in which every object is six times bigger, but instead we think we are looking at a scene in which everything is six times closer.

That is compression.

There is nothing more to it! It is really not rocket science.

Perspective doesn't change on magnification/zooming in.
Perception does, but as above, it can be hard to measure and define the 'compression' through perception effects.

Yes, apparent distance between objects along the line of sight shrinks at longer distances. But in the last few messages I was talking mostly about relative angular sizes, not relative distances.

But what is 'compressed' under this definition?
If you call something a compression, you have to show what is actually compressed.

We can see the compression even without zooming in, as in the image from my previous message above. It's just perspective at a long enough distance from the camera. The scene gets 'compressed' along the line of sight. Apparent distances along the line of sight between the objects shrink, and relative apparent sizes of objects gets closer to their relative physical sizes. It's as if something was squashing the scene along the line of sight.

So it's just the perspective at a distance that gets 'compressed'. Zooming in amplifies this effect for our perception (as you described) but it doesn't create the compression. Again, we can see things 'compressed' in wide angle shots without any zooming in.

Very simple. What you say I said and what I actually said are not the same thing 😊

If you don't see that, that is fine. Others can see the difference.

Now you're just being stupid again by not practising what you preach.

dprevived.com/t/lets-save-this-site/3506/#post-38309

I don't take seriously people who preach one thing and then do not have the ability to do it themselves. For me, they just waste my time 🙂

In any case there are countless videos on the internet demonstrating the compression effect when you zoom in from a given position. If you are too lazy to search for them then you are not really interested and I am not going to spoon feed you.

"Lens compression" is simply the appearance of background objects being closer to the foreground objects when, from a given position, you zoom in.

Yes, from a given position, which determines by the relative distances of objects from a camera, which stays the same, whether you zoom in with the lens or you crop to match in post. The relative distances only change when the camera position is changed. Zooming or cropping enables changes to the overall magnification, but the only way to selectively change the magnification of the background while maintaining the same magnification of the subject is to step forward or backward.

Sorry, I thought it was obvious that it is the distances from the viewer that appear to be compressed.

Take a simple example. Look through a 10x telescope or binoculars at something that is 1000 yards away. It appears to be only 100 yards away. The distance from you (to whatever you are looking at) appears to be compressed by a factor of 10.