Differnece between aps-c and ff sensors 1.5x is in diagonal. Area differnece between aps-c and ff sensor is more than 2 times. That means, if ff sensor is 16Mpx, aps-c crop on this sensor will be something about 7 Mpx. Respectivly, the pixel density of K20D 14Mpix sensor is about the same as on 31.5 Mpix ff sensor.
Sensor area of K20D = 15.6mm x 23.4mm = 365.04 square mm
Sensor area of ff sensor = 24mm x 36mm = 864 square mm
Difference between sesnors = 864 : 365.04 = 2.367x
On Nikon D3 if you use aps-c lens, you will get something about 5.11 Mpix picture.
Last edited by Roberts; 08-01-2008 at 09:51 AM.