Does 30% more pixels = 30% more resolution?

[Dale_Cotton]

If you are working towards prints the answer has to do with square measures, not linear: The 10D has an image file size of 2000 x 3000. Let's use 200 ppi as our test case. at 200 ppi, the 10D gives a print size of 10 inches by 15 inches. The 20D's file size is 2336 x 3504 for a print size at 200 ppi of 11.68 inches by 17.52 inches.

That's an 11.68% increase in resolution. Me and arithmetic don't get along, but I believe that to be invariant with changes in ppi.

OK: Tim has just posted along the same vein. Hopefully, the correlation between print resolution and imager resolution is clear.

[philthygeezer]

How much more detil can I expect to resolve with the 20D given a sharp enough lens?   The 20D has 30% more pixels and reportedly less noise as well.

Can anyone comment?  Thanks.

[Tim Gray]

Here's one way to look at it - at 300 dpi the 10D will print you an image that's 12.3" on the diagonal.  The 20D will give you an image that's 14" on the diagonal.  14/12.3 = 1.14 so a 14% "bigger image".  So not so much an increase as you might expect from your 30% difference in 6.3 vs 8.2.

[blokhead]

The exact relationship: If you increase the area of something by a factor of X, you increase its linear dimensions (length, width, or diagonal) by a factor of sqrt(X).

The sensor's megapixel measurement is an area measurement (pixels wide * pixels high). An increase of 30% in megapixels (megapixels times 1.3) leads to a increase of 14% in the linear dimensions of the print (because sqrt(1.3) = 1.14)