A short while back, someone had posted this link to Ken Rockwell 5D3 user guide.
As one who is always open to learning all I can with regards to best using my new 5D3, I saw this.
Please feel free to comment on this as I find it interesting and useful.
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.
At the 5MP setting, you have 100% R, G and B pixels, exactly as if you were using a Sigma Foveon sensor. If Sigma was selling this, they'd sell the 5MP (S) setting as if it were 15MP (also a lie).
What this means is that the lower resolution settings actually pack away lot more detail than you think. The S (5MP) setting of the 5D Mark III is a lot sharper than any 5MP camera.
M looks almost as good as L for the same reason.
If you're testing lenses, sure, shoot at L, but for everything else, try the settings for yourself, You'll probably get what you need at the smaller settings. For instance, the 11MP setting of the 5D Mark III has way more detail than any of the 12MP (native) Nikon cameras.
The resolution advantage of the 5D Mark III is obvious, even at lower settings. Try them.