Originally posted by Farmer_Terry So yes, perspective does depend entirely on where you stand, but yes, lens length does affect perceived perspective. Two different things.
Yes, but the point is, it is *not* the lens focal length that determines this - it is the *field of view* of the lens. Thus, the effect a 50mm lens has on perceived perspective when viewing a print is *different* depending on sensor size. A 50mm is normal on FF, short telephoto on APS-C, but wide angle on 645 format. And thus, images from that exact same lens will have *entirely different effects* on the perceived perspective in the print depending on what camera it is mounted to.
In other words, your previous statement...
Quote: If I put the same 50mm lens in front of 35mm film and an APS-C sensor surely the perspective in the both resulting images remains the same
... is just *incorrect*. The effect you refer to is *not* specific to the focal length of the lens but to the FOV it produces on the camera you have it mounted to. Thus, it is a 35mm lens on APS-C that would have the same effect on perceived perspective in the print that 50mm has on FF, because both have the same FOV. A 50mm lens on APS-C would have the same effect on perceived perspective in the print that a 75mm lens would on FF, because both have the same FOV.
For that matter, you could have the same discussion without reference to cameras or lenses, but just talking about drawing or painting. A scene depicted with a given FOV has the same effect on perceived perspective whether that depiction was created by an FF camera with a 75mm lens, an APS-C camera with a 50mm lens, or an artist with a pencil. It's all about FOV, not "focal length", which has no meaning for the case of the artist with the pencil.