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12-23-2012, 04:47 PM   #1
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Quick question regarding field of view - FF vs APS-C glass?

Probably a stupid question, but it is something I have never really thought about...

Lets say I have a Pentax A 35 f/2.0 (made for FF) and a Pentax DA-L 35 f/2.4 (made for APS-C)- will the field of view be the same for both? Or will they both be multiplied by the 1.5 crop factor if used on APS-C?

Thanks much.

12-23-2012, 05:00 PM   #2
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DA 35mm

Field of View (Diag)Field of View (Hor)45 degrees (APS-C)38 degrees (APS-C)

A-35mm

Diagonal FOV Horizontal FOV Horizontal FOV on Digital 63 degrees 54 degrees 38 degrees

So based on the information obtained off the lens review database the horizontal FOV is 38 degrees when on a crop camera for both lenses.

The diagonal is not listed, but I would assume its the same.
12-23-2012, 05:10 PM   #3
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They will both have the same field of view. And on an APSC sensor, the FOV will be effectvely divided by 1.5 in both cases, such that the 35-mm-equivalent focal length will multiplied by 1.5. So they will both look like a normal 52.5 mm lens, if you were using 35-mm format film.
12-23-2012, 05:17 PM   #4
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The focal length is a constant that doesn't change based on how big the sensor of your DSLR is. Think of it this way: the frame is the same, but APS-c sees less of it.

Manufacturers take advantage of this fact to drop full-frame support in certain digital lenses to make them smaller/cheaper, but this has no effect on the focal length whatsoever.


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12-23-2012, 05:29 PM   #5
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Their field of view will be the same, but on crop sensors you will see less of it (as in.. the frame is cropped). Because of this, some "APS-C" lenses (like the DA lenses) don't bother having high image quality at the edges - they get cut off anyway. The camera doesn't record them, so meh.
So using a full frame lens on a crop body will work just fine. Its FoV will be the same as a modern digital, APS-C variant of the lens. But putting an APS-C lens on a full frame body would reveal that its border quality is not as high (usually this means vignetting: very dark corners). But! Not all APS-C lenses are.. cutting corners, so to speak. Some work perfectly well on full frame.
12-23-2012, 05:33 PM   #6
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Ok, thanks so much everyone, I understand now.
I really appreciate the help.
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