02-18-2011, 06:43 PM
[quote name='Brightcolours' timestamp='1298032922' post='6221']But, you may wonder, how come the exposure times then remain the same? That is because the ISO is messing things up. ISO says NOTHING about sensor sensitivity, it only says that if you use two different sensors, with probably very different sensitivities, the photographer gets roughly the same exposure time with the same f-value and an equivalent focal length. This is done by applying very specific amplification per sensor.[/quote]
Hm. I guess you should have mentioned that ISO is upped only if the pixel pitch is smaller, not because the actual sensor is smaller.
Also I've noticed that you're mixing field of view and focal length - they're not the same. A lens with focal length equal to 50mm and mounted on FF sensor will have horizontal FOV of around 40 degrees. Mounted on ASP-C sensor, the 1.5x crop factor will effectively reduce the horizontal FOV to 27 degrees, which is roughly equivalent to 75mm lens mounted on FF. What I'm trying to say is that FOV is inversely proportional to focal length, therefore you have to multiply by the crop factor, not divide.
Hm. I guess you should have mentioned that ISO is upped only if the pixel pitch is smaller, not because the actual sensor is smaller.
Also I've noticed that you're mixing field of view and focal length - they're not the same. A lens with focal length equal to 50mm and mounted on FF sensor will have horizontal FOV of around 40 degrees. Mounted on ASP-C sensor, the 1.5x crop factor will effectively reduce the horizontal FOV to 27 degrees, which is roughly equivalent to 75mm lens mounted on FF. What I'm trying to say is that FOV is inversely proportional to focal length, therefore you have to multiply by the crop factor, not divide.