AndyH Loc: Massachusetts and New Hampshire

Difference is in depth of field and blur at the edges of the objects. The tripod didn't move at all, but I may have changed the field a bit in cropping down. I don't have time to go full photoshop here to prove that gravity exists or the earth is round(ish).

I don't care what "Bob" thinks of these images or any others, but I would hate to see newbies and students learning facts that are just plain wrong. If I have time, I'll try a couple of outdoor images on a tripod as well.


We need to call out misinformation for what it is, and if it's repeated often enough after being proven wrong, call it what it is - a lie.

artBob Loc: Near Chicago

Perspective is not subjective. It is a whole field, with architects, computers, artists, architects rural photographers needing to understand its basic truths.
Thank you for trying to help, but your suggested experiment is not sufficient, as you are relying on one point perspective, not full linear perspective.
refer to this diagram and translate your pipe experiment into full linear perspective.

-or-
find a fence with regularly spaced uprights. From across the street shoot it with a short lens, then at the same spot (tripod may be necessary) with a long lens. crop the short lens to superimpose it perfectly over the first upright. None of the others line up. The perspective has been changed. It is MUCH fore evident if you are shooting something that includes nearby and far away. Try it on a city street. Perspective change.

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AndyH Loc: Massachusetts and New Hampshire

Good exercise you've described there, but I would disagree with the first sentence above. Perspective is not subjective, it's a measurable relationship between objects, which Bob has chosen to describe with vanishing points and perspective lines. That's the only thing he's right about, but he's right about that.

I guess I would say "visual appearance" or "apparent perspective" to describe the subjective part of this. True "perspective" is an actual, sciencey thing, no matter how Bob distorts it.

Andy

AndyH Loc: Massachusetts and New Hampshire

Where's that authoritative citation you were going to provide on why changing focal length alone, without changing camera position, changes that full linear perspective? Any professor, any book, heck, even a YouTube Chemtrail video is more than you've offered at this point.

We want students and newcomers to have full facts, not the half truths and bad photos of a "mentally challenged idiot" like me.

I'll be waiting...

<crickets>

selmslie Loc: Fernandina Beach, FL, USA

You are correct. Perspective is purely geometric. There is nothing subjective about it.

The only problem with TonyBot's experiment is the use of binoculars. Each eye captures a separate viewpoint or perspective. That'e great if you want to view the scene in 3D but one eye might see both posts because one of them conceals the other but the other eye might see some of the rear post peeping out from behind the front post. That is two different perspectives.

A camera with a single lens would see only a single perspective from that fixed position regardless of the focal length.

Dossile

As someone with a lot to learn, I am grateful for the discussion. In simplistic form, the argument is over whether or not a picture taken with my Nikkor 70-200 2.8 E set on a tripod at 200 mm and an image taken of that same subject at 70 mm 2 seconds later without moving the tripod and then cropped perfectly to match the 200 mm image, will look the same. With the pictures being taken from exactly the same spot, the factors that lead to image compression are no longer present. To my mind, the two images should look pretty close. However, if I took a picture with the 200 mm, then I walked up to the exact spot necessary to get the exact same field of view with the lens at 70mm, there would be a compression factor present and the perspective and visual effect in the picture would change between the two photos.

If the experiment was done with two different lenses, or a lower quality zoom, the characteristics of the lens would come into play and the pictures would, by that factor alone, look different even if taken from the same perspective (ie. taken from the exact same spot on planet earth). Is that the idea?

RWR Loc: La Mesa, CA

I tried this, didn’t work. The cropped short lens image superimposed perfectly over the post shot with the long lens, but there were no more posts in the frame. Now I’m not sure if I need a longer short lens or a shorter long lens.

artBob Loc: Near Chicago

Where's that comparison of your shots? When I see that, I'll give you a source from a prestigious university.

selmslie Loc: Fernandina Beach, FL, USA

You may think you have a lot to learn but you are way ahead of the OP.

By keeping the camera in the same location the perspective will not change although there will be a narrower field of view with the longer lens.

There are two minor issues that might affect the actual image:

1. Barrel distortion in the wider angle image and pincushion distortion in the telephoto version - the perspective will be the same but the images might not perfectly overlap.
2. The front element of the zoom might move forward slightly but this effect is likely to be too small to be visible in the image.

Clearly the OP does not know enough about photography, geometry and perspective to understand this. You are more observant than he is.

selmslie Loc: Fernandina Beach, FL, USA

My, my. We are on tenterhooks waiting for your great revelation. It ought to be a whopper!

Bill_de Loc: US

I was always taught that focal length does not change perspective. But reading these threads I thought I would use Google and see what's out there. I found a video where the author proved that focal length changes perspective. He had an assistant use a wide angle and telephoto lens. The shot was in a field with a large rock as the main subject and smaller rocks behind it.

She took a shot with each lens and there was a definite difference in perspective. He did point out that when using the telephoto she had to step back to keep the large rock the same size in the frame. HUH!

This was supposed to be an instructional video. Is there any wonder there is a lot of confusion!!!

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BebuLamar

I have a question for the OP. Well you said perspective changes with different focal length lenses. Ok does perspective change with different camera to subject distance with the same lens same focal length?

TriX Loc: Raleigh, NC

This is actually of a continuation of an unending discussion on a previous thread where every professional photographer on the thread and numerous other citations (including one from Ansel Adams) refuted this patently wrong idea, but The OP will not listen to the scores of professionals telling him he is mistaken, hence this new attempt. If you want to understand the facts, rather than this misguided assertion, you might want to review this thread. Restating an incorrect opinion ad infinitum won’t make it true. The assertion was mistaken 14 pages ago, and it’s mistaken now, but like the Furacell bunny, it just goes on and on...
https://www.uglyhedgehog.com/t-549214-12.html#9322963

artBob Loc: Near Chicago

What's your problem? You make it so personal. Do you feel a need for something psychological?

The rest of you, I hope to keep this honest and investigative.
My main take-aways have been that, doing what some said would prove what selmslie and CaptainC claimed, actually proved that linear distortion did occur. Note that neither of these two have posted a visual showing what they claimed would be proof.
The second take-away is that you will get distortion varying from what we humans consider normal if you use a wide angle or telephoto lens. Even if the "geometry" of perspective was the same (think of train tracks heading towards the horizon) for a 50mm and a 200mm lens, our eyes don't read the perspective of train tracks as they appear near the horizon.

The mystery that remains is why the linear perspective itself is distorted by various focal length lenses. (Posting again CaptainC's own photos, taken at the same distance from the same angle, on a tripod, yet showing perspective distortions. The farthest building was given a 1:1 match in the composited photos.) Any ideas?

You ol' stinkers don't need to post all the same bromides. Anyone who cares has looked at them. The problem is perspective distortion is shown to be a fact. If you want to disprove it, why not use CaptainC's method of proving and his own photos to show that.

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AndyH Loc: Massachusetts and New Hampshire

By George, I think you’ve got it!

😎