Originally posted by Bob 256 The pixel count is proportional to the* square* of the sensor size (assuming compared sensors have the same proportions and pixel density). To increase the sensor size by a factor of two requires 4 times as many pixels. Another way to look at it is the the sensor size is proportional to the square root of the number of pixels. Doubling the number of pixels will not get you a sensor with double the linear dimensions.

The best comparison is the K-1 and the K-01, the latter of which is APS-C (the former being FF). These have the same sensor density so it's almost like you took a cookie cutter to the K-1 sensor to get the smaller K-01 sensor (these are 36.4 Mp versus 16.28 Mp). If you divide 16.28 by 36.4 and take the square root, you get 0.669 which is pretty close to 2/3. You can shoot a pic on the K-1 and K-01 using the same lens, and if the K-1 pic is cropped to the APS-C size, you almost can't tell the difference pixel-wise (same number of pixels in each).

I think that I think I know what you're talking about. I may need to reread it a few times.

Math is not, and never was, my strong suit. Thankful that there are folks out there that can figure it out, though!