I' just read the following at kenrockwell website and i am confused. I do realize there is an option to shoot at smaller MPs, but I did not know it is beneficial for image quality. Can some of the tech-smart guys here comment on this? Are you guys shooting at lower MPs?
No one needs 21MP. All it does is slow everything and clog your hard drive.
Try shooting your 5D Mark III at its M (11MP) or S (5MP) settings. If you look at your images at 100%, you'll see that the lower resolution shots are sharper pixel-by-pixel!
When I'm photographing family and friends, I shoot at SMALL JPG. Even SMALL is good enough for great 20x30" prints.
The smaller-sized images out of the 5D Mark III are spectacular. They are much, much sharper and cleaner than images from cameras on which that is their native resolution. When you start with over 20MP, it looks pretty good if you use all those to make 11MP or 5MP.
Why? Because they use less, or no, Bayer interpolation. No digital camera really resolves its rated resolution; they cheat and interpolate up, so at 100% at its rated resolution, no digital camera image is as sharp as a true scan from film.