Originally posted by mhaws So i understand the multiply by 1.5 if you don't have a full frame camera...
If you don't have a full frame camera, you don't multiply anything by 1.5. If you buy a 50mm lens, it is a 50mm lens, just like it says. Only if you also own a FF camera would you occasionally want to multiply the 50 by 1.5 to find what what lens you'd need to us on the FF camera to get the same field of view. But if you don't own an FF camera, there is no need to do that. That would be like driving down the road, seeing your speed in MPH on the speedometer, then constantly multiply that by 1.6 to find out what your speed is in KPH so you'd know if you were speeding in Germany. You're not in Germany, so why would you care?
Quote: If you have a camera that has a 1.5 crop factor and you are shooting with a 50 mm, it would be the equivalent of shooting with a 75mm lens on a Full Frame camera right?
In terms of field of view, yes.
Quote: What I mean is....does it compress as much as a 75mm lens actually would on a full frame camera?
As mentioned, no lens compresses a thing - that's a myth. It's your position relative to your subject that determines perspective. The reason this myth got started is that when using a longer lens, people tend to stand farther from their subjects, which changed the perspective, and some people erroneously assumed this meant the lens caused the change in perspective. But it didn't; it was the change in position. Since a 50mm lens on your camera has the same field of view as a 75mm lens on the camera you don't own and therefore really don't have any need to even be thinking about, you'll stand in the same position to take the picture as you would with the 75mm lens you don't own on the FF camera you don't own. But again, since you don't own that camera or that lens, why think about this?
And if you do insist on thinking about it, why stop at FF? Why not also constantly go around worrying about what focal length on a 645 camera would provide the same FOV? And also on 4/3, and also on 6x7, and 8x10? There's just no point in doing the math unless you actually own both cameras and are interested in buying a lens for one that matches the FOV of a lens you like on the other.