Why does this all look like a deja vu ?
There are many topics that are raised again and again on LL, some of which are raised far more frequently than the topic of 'perspective'. One such topic would be Expose To The Right, or ETTR.
You've provided a couple of links to previous discussions on perspective but have missed out perhaps the longest thread that I link below.http://www.luminous-landscape.com/forum/index.php?topic=61535.120
The reason why I raise this issue again is because I am genuinely amazed that so many apparently experienced photographers seem to be in such a state of denial about this issue and present the most illogical of arguments in order to maintain their position.
Thinking about the reasons for this, I wonder if it's because the thought that any scene as represented in a photograph might not be real, or that it is a distortion of reality, is too uncomfortable. Perhaps people like to kid themselves that the camera really does never lie. And whilst such people might admit when pressed, perhaps grudgingly, that the camera does or can lie, they perhaps kid themselves that it lies only a little bit, or lies only sometimes.
The main argument presented by those who maintain that focal length of lens, or degree of cropping, has no bearing on the perspective of elements, as seen in a photographic image, is as follows.
If one takes two shots from exactly the same position, using widely different focal lengths of lens, resulting in two images with an apparently different perspective, and one crops the wider shot in post processing so it has the same Field of View as the other shot, then both shots will be identical in terms of perspective, although probably not in terms of resolution.
Now to claim that this experiment proves that neither cropping nor focal length of lens changes perspective is where the absurdity comes in, or the Alice in Wonderland aspect.
Let's examine this absurdity, but first the facts which I hope we agree upon.
(1) Two images can 'appear' to exhibit a different perspective when taken with different focal lengths of lens.
(2) All photographs are 'appearances', not to be confused with reality.
(3) The image taken with the wide-angle lens clearly and unambiguously gives the impression
that certain objects, because of their small size in relation to other objects or elements in the image, appear
(4) The image taken with the longer focal length gives the impression that those same elements that appear so distant in the wide-angle shot are now much closer to the viewer. The perspective from the position of the viewer is therefore different because it appears
different, and all photographs are appearances.
(5) If one crops away the large objects in the foreground of the wide-angle shot that are responsible for creating the impression that elements in the background are so distant, lo and behold!, surprise! surprise!, the perspective in the wide-angle shot now
appears the same, provided
one views same size prints from the same distance.
Now let's examine what this experiment really does demonstrate, in my opinion.
(1) If we have to crop the wide-angle shot in order for the image to have the same perspective as in the narrower-angle shot, then that clearly demonstrates that cropping affects perspective, surely.
If cropping doesn't affect perspective, as JJJ claimed it doesn't earlier in this thread, then why is it necessary to crop the wide-angle shot? Ah! Perhaps JJJ thinks that the different perspective, as seen in the wide-angle shot before cropping, is merely an illusion, an aberration, a distortion, a trompe l'oeil, and that such illusions of perspective can always be magically dispelled through the act of cropping. Wow! Are we now back into 'Alice in Wonderland'?
What this experiment really demonstrates is the relationship between cropping and focal length of lens, and the fact that any lens used with a given format of camera can be effectively converted to a longer focal length through cropping, but unfortunately with consequent loss of resolution.
The experiment also demonstrates that in order to get photographic images to display the same perspective when the shots are taken from the same position, it is necessary to either use lenses which have the same focal length, or create the same equivalent
focal length through cropping in post processing.
But what happens when we want the perspective that only a wide-angle lens can provide
, and all we have is, say, a normal lens? No problem, I can hear Bart and JJJ declare. Just take a number of shots and stitch.
Really! I've never succeeded in taking shots for stitching a wide panorama without moving the position of the lens between shots. What's the technique here, Bart? On the one hand you're claiming that only position determines perspective, and that only a change in position results in a change in perspective, not a change in focal length, and to demonstrate this principle you are changing the position of the lens in order to create the equivalent of a single wide-angle shot which has been taken from one precise and exact position.
Something fishy going on here!