Talk:Field of View

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(close focusing increases FoV: new section)
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I believe this phenomenon is known (in cinematography at least) as "focus breathing". In my own limited experience, the FoV is slightly larger when close-focusing compared to infinity focus. Presumably it is more pronounced in some lens designs than others. If I understand correctly, the lens' specified focal length (eg nikon 50mm) will be correct for infinity focus, so at its minimum focusing distance the lens' FoV would be better represented by a focal length number of -say- 49.1mm ? For the purposes of lens correction calibration, would it be appropriate to compensate for close focusing by reducing the focal length variable ? or would that throw some other parameter(s) out of whack ? --[[User:Beeswax|Beeswax]] 13:57, 27 January 2011 (UTC)
 
I believe this phenomenon is known (in cinematography at least) as "focus breathing". In my own limited experience, the FoV is slightly larger when close-focusing compared to infinity focus. Presumably it is more pronounced in some lens designs than others. If I understand correctly, the lens' specified focal length (eg nikon 50mm) will be correct for infinity focus, so at its minimum focusing distance the lens' FoV would be better represented by a focal length number of -say- 49.1mm ? For the purposes of lens correction calibration, would it be appropriate to compensate for close focusing by reducing the focal length variable ? or would that throw some other parameter(s) out of whack ? --[[User:Beeswax|Beeswax]] 13:57, 27 January 2011 (UTC)
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: Exact FoV does depend on even more factors. Details are explained in [http://www.janrik.net/PanoPostings/NoParallaxPoint/TheoryOfTheNoParallaxPoint.pdf Rik Littlefield's paper about the no-parallax-point] --[[User:Erik Krause|Erik Krause]] 17:48, 28 January 2011 (UTC)

Revision as of 18:48, 28 January 2011

in the formula

FoV = 2 * atan \frac{35}{2 * Focal Length}

The "35" should be some "length" because it is divided by a length, and should become unitless. Of course the length is the size of a standard negative: 35mm. If you want to "ignore units" as most americans like to do, it should note that "Focal length" is in mm. But more accurate is:

FoV = 2 * atan \frac{35 mm}{2 * Focal Length}

Should I just edit this into the main page, or should some discussion be held first? -- REW.

Just edit. Actually a "35mm" negative is 36mmx24mm in size. 35mm is the width of the entire film, including perforation etc. Since the formula is universal, I changed it to "size". (This error was pretty old, thanks for pointing it out) --Erik Krause 10:59, 11 June 2009 (UTC)

close focusing increases FoV

I believe this phenomenon is known (in cinematography at least) as "focus breathing". In my own limited experience, the FoV is slightly larger when close-focusing compared to infinity focus. Presumably it is more pronounced in some lens designs than others. If I understand correctly, the lens' specified focal length (eg nikon 50mm) will be correct for infinity focus, so at its minimum focusing distance the lens' FoV would be better represented by a focal length number of -say- 49.1mm ? For the purposes of lens correction calibration, would it be appropriate to compensate for close focusing by reducing the focal length variable ? or would that throw some other parameter(s) out of whack ? --Beeswax 13:57, 27 January 2011 (UTC)

Exact FoV does depend on even more factors. Details are explained in Rik Littlefield's paper about the no-parallax-point --Erik Krause 17:48, 28 January 2011 (UTC)
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