Rob-F
Likes Leicas
That is consistent with what I calculated myself. at 300dpi, and using the whole sensor, 24MP would only make a 13.3" by 20." A 4:5 aspect ratio would use 20MP of the 24MP available. To cover 16" x 20" with 20MP would result in 250dpi. That's a bit lower than the standard; it's fudging a little; but for me, I couldn't see any difference between 300dpi vs. 250 with the Canon 9000 printer I had. So I was just thinking in approximate real-world terms when I wrote that. I don't see any disagreement, I think we are on the same page. (If we must have 300dpi from 20MP at 4:5 ratio, we are limited to 13.33 x 16.66 inches.)What you're calculating makes little sense to me.
The old standard of a 35mm slide or negative that was well exposed and well focused was the ability to make a clean 16x20 inch print, viewed at normal viewing distances of about 3-4 feet. The standard for making such a print from an inkjet printer is 300 ppi output density.
A 16x20 is a 4:5 ratio image where 35mm format is 2:3 ratio, so we can only approximate the size, full frame. If the long dimension of a 35mm frame is fitted to the long dimension of a 16x20 sheet of paper at 300ppi, that means 20" @ 300ppi = 6000 pixels. The short dimension of the frame at that resolution will come out to 13.3 inches, at 4000 pixels. 6000 x 4000 pixels is 24 MegaPixels.
G
Rob