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14-24 but .....with crop
#5
[quote name='Rainer' timestamp='1295116608' post='5540']

This appears to be wrong.



Lets calculate it:



The formula for the field of view of a rectilinear corrected lens is:



FOV (rectilinear) = 2 * arctan (frame size/(focal length * 2))



So, with a 14mm lens and a fullframe camera, we get



FOV-horizontal = 2 atan( 36 / ( 2*14) ) = 104 degrees



With a 24mm lens, we get



FOV-horizontal = 2 atan( 36 / ( 2*24) ) = 74 degrees



With that, lets calculate, at which framnesize the 14mm lens projects the 74 degrees ...



74 deg = 2 atan( xx / (2*14) )

37 = atan( xx / (2*14) )

0.75 = xx / (2*14)

xx = 0.75 * 2 * 14 = 21mm



Ok ... If we take the image of the 14mm lens (36mm wide) and we want to crop it

to an image as if it was from a 24mm lens, we have to crop it at 21mm ...

this is 21/36 = 58 percent of the image (or factor 0.58) ... but we also have to

crop the heights accordingly ... so, the Megapixels are reduced by the square of 0.58

which is 0.34x ... so from the original 24mpix you are left with only 8mpix.



Just my 2 cts...Rainer

[/quote]

All that for only 2 cents? Boy, that is a steal!
  


Messages In This Thread
14-24 but .....with crop - by ficofico - 01-15-2011, 05:55 PM
14-24 but .....with crop - by blende8 - 01-15-2011, 06:08 PM
14-24 but .....with crop - by ficofico - 01-15-2011, 06:31 PM
14-24 but .....with crop - by Rainer - 01-15-2011, 06:36 PM
14-24 but .....with crop - by Brightcolours - 01-15-2011, 06:58 PM
14-24 but .....with crop - by genotypewriter - 01-15-2011, 07:13 PM
14-24 but .....with crop - by Brightcolours - 01-15-2011, 07:17 PM
14-24 but .....with crop - by genotypewriter - 01-15-2011, 07:21 PM
14-24 but .....with crop - by blende8 - 01-15-2011, 07:27 PM
14-24 but .....with crop - by Brightcolours - 01-15-2011, 07:37 PM
14-24 but .....with crop - by Rainer - 01-15-2011, 08:05 PM
14-24 but .....with crop - by Rainer - 01-15-2011, 08:22 PM
14-24 but .....with crop - by Rainer - 01-15-2011, 08:40 PM
14-24 but .....with crop - by blende8 - 01-15-2011, 09:04 PM
14-24 but .....with crop - by genotypewriter - 01-16-2011, 06:16 AM
14-24 but .....with crop - by Rainer - 01-16-2011, 09:36 AM
14-24 but .....with crop - by genotypewriter - 01-16-2011, 09:55 AM
14-24 but .....with crop - by Rainer - 01-16-2011, 11:06 AM
14-24 but .....with crop - by genotypewriter - 01-17-2011, 03:54 AM
14-24 but .....with crop - by Guest - 01-29-2011, 01:56 AM

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