artBob Loc: Near Chicago

In the topic "Does perspective change when you change the focal length?" I was not allowed to reply.
Here's what I wanted to write:
"What bigotry and ignorance. I used Andy's own photos (can be seen towards end of "Does perspective change when you change the focal length?", and AGAIN showed that he and others who deny that focal length changes perspective are wrong. Since scientific experimentation and free speech have been shut down here, I am going to post my response to Andy and the original poster who banned me, in my own topic."
I also would like to tell some of the people on that thread the following, in case they follow here:
"Please stop calling people names, for it shows the weakness of your argument.
"Please stop calling people ignorant. In this case, apparent ignorance of linear perspective on the part of some called into question extensive knowledge on my part--I had to teach the damn stuff. Tough. I know many people cannot perceive it, fail at it. However, to accuse of ignorance actually reveals ignorance."

So, here is a transparency of both Andy's photos, with perspective lines indicated. The perspective is indeed changed. I'll also upload his photos, so others can explore.

Also, I found a stock photo shot by a wide angle lens, and drew the perspective lines on it. They are all over the place, thus false. I then corrected for the lens in Photoshop, and indicated the perspective lines we (and generally a 50-70mm lens sees) see.

Finally, CaptainC, whose post started the whole discussion, posted four photos, all shot from the same place, same distance, on a tripod. He had said those who thought lenses distorted perspective were wrong, and that could be proven by cropping the shorter length lens photo and overlaying it on a tele photo. I did that, because I thought, "Wow, really? That goes against what I had thought." So, I looked at two of those photos, lining up the same, most distant building in each so they matched, and found that perspective indeed had changed. Perspective lines for each shot, one set blue, one set red are overlaid.

If anyone wants to join in the discussion, with insight and honesty, please do. Mysteries remain.

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AndyH Loc: Massachusetts and New Hampshire

Bob, you are certainly not understanding this, and perspective is most definitely not changed by changing focal lengths. Please do not mislead newcomers and newbies on this point any further.

I don't see that you've been "banned" from responding in the original thread. As I pointed out, ON THESE IMAGES THAT YOU COPIED AND ALTERED WITHOUT ASKING PERMISSION, these were handheld snapshots, and the position inevitably varied by a little bit. The essential perspective can be seen from the relative sizes and alignments of the near object (the inkstand), the middle object (lamp), and more distant objects (chair and magazine stand). They are very close to the same size in both images, and lined up with the same foreground objects on the inkstand - in other words, the perspective has not changed.

What little variation you show with your vanishing point lines is entirely due to inexact location of the camera in both shots. You want to see some real change in perspective? Take a look at these images, which I also posted in the original thread. Now you can see the classic expansion and compression of space we associate with lenses of different focal lengths, but it's because I changed the camera LOCATION, not because of the change in focal length. Draw your lines on both of these and you'll see what is meant by a change in perspective. The divergence in the first images is tiny and due to slight movement of the camera position - look at these two images and you'll see what really does change the perspective - MOVING the camera, not switching lenses or focal lengths.

You're a smart man and a terrific photographer. I do not understand why you don't understand this concept, which is outlined in every single photographic course, workshop, book, or document on the subject any of us have ever seen. You are entitled to your opinions on anything, most of which I respect.

However you are not entitled to what the current WH press secretary called "alternative facts" or what others might call "untruths". I am afraid that you are seriously misleading others here, especially newbies, by your continued misrepresentation of factual information.

Andy

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artBob Loc: Near Chicago

No, your idea is not "outlined in every single photographic course, workshop, book, or document." I hired the photo prof and checked out the books. I did a lot of research because of this misinformation about perspective. Besides your example, why are you ignoring the other, definitive ones? I truly don't get it.

I think the root cause is that most photographers did not have a rigorous course in perspective. That ignorance is evident to anyone who had. They then, thinking they have the answer because of original misinformation, cherry pick sources that confirm their bias.

My hope is that newbies LOOK at what I have posted, EXPERIMENT for themselves, and shoot photos without harming themselves with bad info. I think you have the same goal, that photogs shoot photos without harming themselves with bad info. It's just that I have presented the visual evidence to show my tactics are right, while you have not even though you claim to have done so. Let's hope newbies are smarter than one of us.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Rooflines are curved - how do you deal with that? And not all of your drawn lines are accurately superimposed. Oh, I suppose that "fudge factor" helps you to make your point. Sorry. Even on a new thread, you are still wrong.

Optical aberrations do not prove (or disprove) perspective changes. Changes in the relative sizes of elements in the foreground, middle ground and background are what clearly indicate changes in perspective. Like when you take a shot with a 100mm lens and move back to get a similar composition with a 200mm lens - there will be a very clear change in perspective. Not these subtle things you are using as "proof".

You need to come up with something more substantial. Like I did. And if you want to superimpose an image on another at least learn how to align the images correctly. And be sure that the images are exactly the same angle of view. And be sure the camera has not moved. And be sure that you can support what you are talking about with at least 2 primary and reliable sources.

AndyH Loc: Massachusetts and New Hampshire

Now you're just outright lying. Show us one citation, any citation, from any authoritative source, that shows that changing focal length WITHOUT CHANGING CAMERA LOCATION changes perspective. Go ahead, just one. I dares ya'.

You can't because there isn't one. Find one of your many professors, courses, or other sources that states that "CHANGING FOCAL LENGTH WITHOUT CHANGING CAMERA LOCATION ALTERS PERSPECTIVE". Just one authoritative source. You can't because there isn't one. Either do so or tell everyone whether you're just ignorant of the facts or are deliberately lying to mislead others.

Ain't no other options.... Show some facts or shut up and stop trying to mislead others.

AndyH Loc: Massachusetts and New Hampshire

Got those citations yet? Or were you too busy writing PMs calling me an idiot, mentally challenged, and wimpy to find them?

I know it's a waste of time, but I'll be waiting....

AndyH Loc: Massachusetts and New Hampshire

Got those citations yet? Or were you too busy writing PMs calling me an idiot, mentally challenged, and wimpy to find them?

I know it's a waste of time, but I'll be waiting....

artBob Loc: Near Chicago

QED re Andy.

I am sorry this has become muddied up with personal things. I hope we can stay with a good discussion about perspective being changed by lenses, referring to examples. A lot purportedly showing that lenses do not affect perspective were shown in the other thread, "Does perspective change when you change the focal length?" Those examples were dealt with, primarily showing that their claims were false (with real pix and noting overly controlled situations), and the explanations were very poor, lacking in required knowledge of linear perspective. So, you might want to go there first. Certainly not required.

I suggest we stay with the examples, and show why and how they are wrong if that is your decision.

artBob Loc: Near Chicago

If "rooflines are curved," that immediately tells you the linear perspective is off.

"Changes in the relative sizes of elements in the foreground, middle ground and background are what clearly indicate changes in perspective."
FALSE. Linear perspective is based on parallel lines converging on a vanishing point at eye level. The spacing of objects also follows certain laws, which any long lens shot, as objects become more distant, clearly botches up. (see the example) Some call it "optical compression," but it remains bad perspective, an would not appear in a standard lens.

"You need to come up with something more substantial."
Is that a JOKE? I used CaptainC's own examples, shot on a tripod, from the same distance, at the same angled for my proof. You have SHOWN nothing of proof.

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AndyH Loc: Massachusetts and New Hampshire

Okay, I found a pocket tripod in a pocket of my bag and shot two images quickly in snapshot mode. One is at 70 mm and the other is at 18 mm cropped down to the same approximate view (quickly, I don't have time to merge layers and play with transparency).

Now show me the difference in perspective. Any change in the relative positions or the apparent distance between the objects in this photo. You have my position to draw your silly imprecise vanishing point lines anywhere you want. Tell me there is any difference at all in the perspective of these two images.

Go ahead. I'll be waiting for that along with the citations on how changing focal length alone changes perspective.

Please stop spreading misinformation. Children might be reading this.

artBob Loc: Near Chicago

No, YOU do it. I have done it with better photos than these, and you still persist. Go ahead and superimpose them and SHOW us. I assume you are just gazing at these simple examples for your judgment. First mistake. More importantly, shoot a downtown scene or such so you get some depth. As I wrote, if you want to shoot a chair (or desk in this case) at 6 ft. your whole life, you don't have to worry about perspective distortion very much.

As to the horrid snark about spreading information, just refrain from your personal insights and stick to facts please.

selmslie Loc: Fernandina Beach, FL, USA

No, it doesn't. It immediately suggests barrel distortion. Apparently you are not familiar with the term even though I suggested you read about it and other forms of lens distortion.

Things don't seem to be going very well for you here on your own thread either. You appear to know less about photography and geometry than you let on.

AndyH Loc: Massachusetts and New Hampshire

Sorry, you're the one attempting to prove a non-factual point. You're the one who likes to draw lines. Anyone with reasonable eyesight can see that there is ZERO change in perspective in those images, even though the focal length on the first one is more than three times the length of the second shot. Gene has already done the same thing at a distance, and your edits showed nothing but a tiny bit of distortion, no changes in perspective at all. In fact you haven't shown what you've said on any of your creative endeavors.

Still waiting for any authoritative source for your misinformation <cough> lie <cough> that changing focal length changes perspective.

I'm sorry if you thought that was publicly snarky, I just didn't want to be "wimpy" by not saying it out loud, as you accused me of in that courageous and articulate PM you sent me. Your mama must be so proud.

I'm brave enough to say that you're spreading misinformation and lies, and I don't have to resort to private messages calling you an idiot or mentally challenged - that private name-calling thing is your gig. I'm not assaulting your character for doing so, but whatever your motivation, you are repeating and spreading factually untrue statements.

Whatever opinion I, and other members more respected and professional than I, may hold, you are spreading misinformation here, misinformation that is misleading to others. You persist in doing so, despite having been called out and proven wrong. I'm going to continue to call you out.

You've been asked to provide any authoritative source for your "fact" that changing the focal length of a lens alone changes perspective. It doesn't.

Put up or shut up. Your choice.

BebuLamar

There are very minor differences in the 2 pictures but that I think because Andy didn't exactly shot the 2 shots at the exact same distance. Somehow the different in depth of field makes it difficult to measure the size of the white bookshelf in the background. But no changing the lens focal length didn't change the perspective.

TonyBot

Please, artBob, you are incorrect. You should look up the meaning of *perception*, and discover that it is a subjective word - and not necessarily influenced or related to actual facts. AndyH's examples beautiful proof of his accuracy and your misunderstanding.

Try this, please, and see what the majority of us understand:
Pound two identical pipes into the ground to the same depth. The height should remain the same. Stand back 20 feet and look directly at them so you only can see the closest one. Take a pair of binoculars and WITHOUT MOVING THE IMAGING OBJECT - YOUR EYES, view the pipes. You still see the same thing, the "perspective" has not changed - only the field of view. If the rear pipe (previously hidden) can now be seen - you moved.

Now take your diagrams, and set up the same experiment in two dimensions, laid out flat. Pipe A, Pipe B, Imaging object (A...B..............C). Draw your lines. There is NO WAY you can see around the first pipe without moving one of the points. Physic/Optics, whatever. Your FOV may change, but the perspective cannot: A will always be the same proportion as B, whether you use just your eyes, a 7x30 binocular, 3x20 opera glasses, or the Hubble Telescope UNLESS YOU MOVE one of the elements.

As i said = perspective is a subjective word.

Starting a new discussion (?) is not going to change physics.