Originally posted by house When the field of view is identical the perspective and compression is identical?
Switching lens/sensor combo for the same field view results in identical perspective.
Imagine you are standing in front of a very wide palace, at a distance of 120 feet, and there is a row of flags in front of the palace, from the left end to the right end.
Without moving from your spot, say you want to capture a photo of the palace, and have each flag in the picture. Say you use an 85mm lens, and you're using a film camera.
Now you step up closer to the palace by 100ft, so you're now only 20ft away from the palace. To get every flag in again, you probably need an 20mm lens now.
Now compare the photos taken. They both include all the flags, from left to right. But they look very different. In order for the 20mm lens to squeeze in every flag, at such a close distance to the palace, it would have to distort the perspective. Diverging lines for example, would diverge very dramatically, more so than in real life.
So the 20mm lens, a wideangle, as compared to 85mm, introduces a visible form of distortion (which can actually look very nice when used right).
The key point here is that a wideangle lens, by its very design, introduces perspective distortion to an image that it casts.
Now, consider using an FA31 to snap a given scene, with a given FOV. Assume you're using an APS-C sensor now, eg. with a K-3. In fact, the image being captured (and also what is seen in the viewfinder) is just a crop, a portion, of the real, larger image being cast by the lens. Hence we're only seeing a part of the real picture; the effect is the same as cropping away the edges of a picture, and then magnifying the remaining portion until it comes back to the original size of the image before being cropped. In other words, there is magnification going on, of the middle uncropped portion of the picture. Or to put it another way, in APS-C, the FOV has been narrowed. That is, the FOV feels the same as if we were using an FA43 on a Full-frame sensor (here the entire image cast by the lens is captured/seen - no cropping).
So the FOV appears the same, but remember that the image cast by the 31, it being a wideangle lens, would inherently have that distortion effect (although milder than that seen in a 20mm).
Whereas an FA43, being a true-normal, does not generate this distortion effect.
Bottom line, the FOV appears the same, but the FA31 image has that perspective distortion effect in it.
Last edited by KDAFA; 05-18-2016 at 07:38 AM.