Originally posted by mee Thank you for that link but I seem to be missing some key element in this.. The first line you state there seems to conflict with the second.
I mean in the article it states "Another way of looking at it is that the field of view is narrower on APS-C compared to full frame given the same lens"
So the field of view does change? Perhaps, if it does not change, you mean the sensor 'sees' the same FoV with that 645 lens regardless of camera body to which it is affixed, the difference is that the sensor (for instance a K3 uses) is smaller on APS-C and thus that same field of view is contained in a smaller view? Or just that part of that FoV is clipped due to the smaller sensor size?
ahhhhhhhhhhhhh.
I guess I'll read that article over and over again..
The effective field of view by all means changes; the focal length does not.
Basically, since the K-3's sensor is smaller, it only sees a fraction of what the lens actually covers. With a bigger sensor (or piece of film) you'd be able to see more of the image circle.
Make sure you understand the above before reading on.
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Now, here's what a lot of people get wrong about this whole crop factor thing. Many believe that a shorter lens designed for a larger sensor format, say a full-frame FA* 300mm, would be "equivalent" to a 450mm when used on APS-C, a smaller format.
This is only correct if you compare the field of view of a hypothetical 450mm lens on full-frame to the field of view of a 300mm on APS-C.
People think you automatically get "more zoom" on APS-C, but the reality is that focal length is a fixed optical property of the lens. So, you gain absolutely nothing (in terms of reach) by mounting a full-frame 300mm on an APS-C camera compared to mounting an APS-C only (i.e. DA) 300mm on an APS-C camera. What you do get is a tighter field of view than you would with the same 300mm lens on full-frame, and thus smaller formats are better for telephoto shooting since you don't need as long of a lens to isolate a distant subject in the frame. Conversely, larger formats are better for wide-angle photography since you don't need as short of a focal length to get an ultra-wide field of view.
That's all there's to it- hope I didn't lose you!
Adam
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