01-15-2011, 07:21 PM
[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]
Uhhh...
14mm = 104.3 degrees (horizontal)
24mm = 73.7 degrees (horizontal)
Assuming 24MP = 6000x4000 pixels,
6000/(104.3/73.7) ~= 4240 pixels wide
Therefore, at a 3:2 aspect ratio the image would be ~= 4240x2827 = 11986480 pixels = 11.99MP ~= 12MP
But as I said... 12MP from 864mm[sup]2[/sup] (FF area) is likely to be better than 12MP from 431mm[sup]2[/sup] (the cropped area on the 24MP FF sensor).
GTW
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]
Uhhh...
14mm = 104.3 degrees (horizontal)
24mm = 73.7 degrees (horizontal)
Assuming 24MP = 6000x4000 pixels,
6000/(104.3/73.7) ~= 4240 pixels wide
Therefore, at a 3:2 aspect ratio the image would be ~= 4240x2827 = 11986480 pixels = 11.99MP ~= 12MP
But as I said... 12MP from 864mm[sup]2[/sup] (FF area) is likely to be better than 12MP from 431mm[sup]2[/sup] (the cropped area on the 24MP FF sensor).
GTW