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01-02-2012, 06:46 PM   #1
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Formula for sensor size and crop factor?

Hi,
is there an easy way to determine what lens will do what angle in mm going from a former full size SLR frame to a APS-c sensor with a 1.5 crop factor?

Sorry if this has been asked before...

01-02-2012, 06:52 PM   #2
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01-02-2012, 06:55 PM   #3
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01-02-2012, 07:35 PM   #4
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The question does not make sense as asked - angles are not measured in mm. It sounds like you are simply asking how the crop factor is applied, and the answer is, the word "factor" is taken literally. That is, you multiply. So a 50mm lens on APS-C format will have the same field of view of as a 75mm lens on 135 format. If you literally want to know the angle - measured in degrees, not in mm - there is indeed a formula for that, but I'd have to Google it...

01-02-2012, 08:04 PM   #5
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There is a Photographer's Calculator here that provides a number of capabilities. The Pentax crop factor (focal length multiplier) is 1.53.
01-02-2012, 10:14 PM   #6
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QuoteOriginally posted by Marc Sabatella Quote
The question does not make sense as asked - angles are not measured in mm. It sounds like you are simply asking how the crop factor is applied, and the answer is, the word "factor" is taken literally. That is, you multiply. So a 50mm lens on APS-C format will have the same field of view of as a 75mm lens on 135 format. If you literally want to know the angle - measured in degrees, not in mm - there is indeed a formula for that, but I'd have to Google it...
Correct,
what I tried to ask is for
Lens Equivalence / Diffraction Calculator
which the next poster has send a link to.
Thank you all very much.
01-02-2012, 10:25 PM   #7
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AOV= 2*ATAN(diag/(2*degs))*(180/PI)

where diag= frame diagonal in mm
and degs= focal length in degrees

35mm full-frame diagonal= 43.3mm
Nominal APS-C diagonal= 30.1mm
Actual K20D diagonal= 28.1mm
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