Originally posted by Yamanobori This a common mistake. Linear perspective comes from a ratio of object distances--you can two picture at two different object distances and achieve the same linear perspective. Since we think of an image as one thing, what is foreground and background changes when you change focal length or crop. Since the ratio of foreground to background distance changes, so does the perspective of the image--landscapes have very different perspectives because of focal length simply because of that. (The ratio of objects in the frame do not change, but a picture is more than some arbitrary choice of objects, but you still can change distance to those same objects and maintain the same perspective or image size ratio and so this is a relative problem, not and absolute one.)
The other way to think of this is that the focal length or crop changes the final magnification of the image--we think of display size is constant. In two point perspective, displacing the points changes perspective. Change in magnification has the same effect.
The great thing is, you can actually see this effect in your photography.
This is news to me as well.
As far as I've ever heard or read, distance to subject is the
only thing that affects perspective. I wonder if you're talking about something besides the standard definition of perspective... Convergence, maybe?
Consider these crops of different focal lengths, all taken from the same distance to subject and cropped to gain the same framing. Note the relationship between the subject and the background elements - there is no change, because the distance to subject did not change.
^^ Taken from
this link.
Here's another descriptive article on perspective, from --->
luminous landscape.
Perhaps you can show some images that illustrate what you're talking about, or provide a link, I'd like to know more and especially would like to know if my understanding of perspective is in need of update.
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