Originally posted by Cannikin Did you even try what I said? Did you even look at the photos I pointed you to? It would take less than 30 seconds to look at them, a lot less than it took you to post this. Here, since you can't be bothered to click on a link, I will post them again for you:
70mm:
70mm cropped:
130mm:
I didn't move the camera between shots. Tell me, what has changed about the perspective even after I almost doubled the focal length (ignore the slight exposure difference)?
EDIT: See two posts down for an even more extreme 10mm vs 50mm example.
Would you also "trust your eyes" which tell you the Earth is flat, or that the Sun moves around the Earth? Because they sure seem like it at first glance. Yet these are illusions that are false, just like "focal length changes perspective" is an illusion that is false. The geometry of perspective has been well established for thousands of years since Euclid. So-called "perspective distortion" seems unnatural because human eyes/brains, with their fixed AOV, are not used to viewing things like that. If you want more reading material, you can start by reading the third paragraph in the introduction section of this article:
http://en.wikipedia.org/wiki/Perspective_distortion_%28photography%29 Ok, since my comment was never deleted from the response as I requested, and the rough language stayed, I guess I'll just throw a question out there...
Your test basically proves that if you crop down a FF image to APS-C size, you get the exact same image you'd get from an APS-C camera. That however, is not the real world scenario I was referring to. And I don't think I'm a good communicator, so hopefully I'll be able to express what I'm trying to say with a real world, practical example.
Let's say I'm in my back porch and I want to take a picture of my wife including the background behind the porch - there's a downhill, lot os trees in the distance, etc. Let's say I have two cameras - one APS-C and one FF. I pick up the APS-C and to be able to put my wife and the background both in the picture, the longest lens I can use is my 35mm lens (and this could happen in a variety of other situations where I can't back off with the APS-C camera and take the shot from further back). So I take the shot, and I see that the background is compressed.
Then I pick up my FF camera and put a 55mm lens on to get the exact same composition standing on the exact same spot (my K20D's crop factor is about 1.53 so the equivalent for 35mm is 53.55mm - 55mm is the closest).
Will the background in both pictures look the same, or will it look different? I think it will look different. When I look in the viewfinder it's different and that's what I had been referring to. I will try to get this test done with my K20D and my film Pentax - but since neither camera has 100% viewer coverage and the lenses aren't exact equivalence, it won't be a scientific test by any means. But this is the real world scenario - to try to get the same composition from the two cameras, standing exactly on the same spot. That is what I had been trying to say all along. I think it's a far more practical example than taking a FF shot and trying to crop it down.