This is fact: it should settle the discussion once and for all, but I know perfectly well that that's not the objective in some minds: the objective is making a contradictory argument that holds the delusion of a morsel of truth when, in reality, it's bogus.
That's usually the time when a thread's worth abandoning for good.
I only accept facts that make sense, Rob. JJJ has made a very categorical statement as follows:
Cropping has zero effect on perspective, nor does print/sensor size or viewing distance and the biggest myth of all, focal length.
So let's examine this statement from a rational and logical perspective. First, let's take the phrase, "Cropping has zero effect on perspective".
The question that immediately springs to my mind here is, "The cropping of what
precisely has zero effect on the perspective of what
I can find numerous examples where cropping really does have zero effect on perspective, just as I can also find numerous examples where cropping has a very clear and obvious effect on perspective. I'll mention a couple.
As I sit at my computer cropping an image that I'm processing, I'm quite certain that the cropping of that image on the monitor has no bearing whatsoever on the perspective of the elements in another photographic print that is hanging on the wall. The two are obviously unrelated.
Okay! That's silly you're probably thinking. Obviously JJJ is referring to the cropping of a specific
image taken with a specific
lens, and he's referring to the perspective of specific
elements in that image.
So let's talk about a specific image and try to imagine how the perspective of elements in that image might change after cropping, in accordance with the following definition of perspective which you may or may not agree with. If you don't agree with this definition, then that could be the cause of the confusion.
The definition I'm using is as follows: "The appearance of objects, buildings, etc, relative to each other
, as determined by their distance from the viewer, or the effects of this distance on their appearance", and I'm applying this definition to photographic images.
A key concept in this definition is, 'appearance of objects relative to each other
'. Now surely it's not difficult to appreciate the consequences of removing objects within a scene by cropping them out so they no longer exist. Do I have to spell it out?
An object in a photographic scene may appear small and distant relative to another object in the foreground which is larger and therefore appears closer. If one removes the larger object (or objects) in the foreground through cropping, then clearly one has broken a relationship and therefore changed the perspective in at least two ways. (1) One or more of the elements in the image has no perspective at all because it no longer exists. (2) The remaining elements in the image have a changed perspective due to a change in the relationship
with other objects in the image that no longer exist.
How anyone could argue with this obvious fact beats me. But I do understand what JJJ and others are trying to say in their muddled way. I believe they are trying to say that the perspective of elements in two images of the same scene with the same FoV
, will only be influenced by the position from which the shot was taken. By what process that equality of FoV was achieved is irrelevant to the perspective of the elements in that image. The equality of FoV could have been achieved by using different focal lengths of lenses with different formats of cameras, or it could have been achieved by different degrees of cropping in post-processing, using the same focal length of lens on different formats of cameras.
The main point here is that different focal lengths of lenses may have been required, or different degrees of cropping may have been required to achieve that equal perspective, therefore it is not correct to claim that cropping or focal length has no bearing on perspective.
correct to say is that changing position will always
affect perspective to some degree, whereas cropping and/or changing focal length of lens may not always
change perspective, but sometimes it might.
An example of achieving equal perspective using different focal lengths of lens would be using a 50mm lens on a Canon 7D and an 80mm lens on a Canon 5D2. Provided the shooting position is the same, and provided one does not perform additional and different cropping during post-processing, the perspective will always be the same in the images from both cameras. The image from the 50mm lens on the 7D receives more in-camera cropping than does the image from the 80mm lens on the 5D2, and is therefore said to be equivalent to an 80mm lens on the 5D2. However, a 50mm lens on a 7D is not equivalent
to a 14mm lens on a 5D2, and without significant cropping of the 14mm shot in post-processing the 14mm lens will produce an image with a very different perspective, even after correction for volume anamorphosis.
I don't think I can make this much clearer, but if anyone thinks I am presenting a fallacious, bogus or muddled argument, then please point out the flaws in my logic.