5Dmk2, 5Dmk3, and D800 sensor measurements
Here's a link to an article with newly-released sensor measurements from DxO Labs comparing 5Dmk2, 5Dmk3, and D800.
Until 1600 ISO the D800 has much better dynamic range, in spite of having pixels 1.5x smaller !
The improvement from mk2 to mk3 in terms of SNR appears to be only 0.5 fstops in 3.5 years with pixels of same size.
How those measurements translate to real-word results remains to be seen, but I've noticed that Lloyd Chambers, who makes a living by pixel peeping (he runs a paywall review site) wrote "As for the Canon 5D Mark III, it’s no longer April Fools day. I will give Canon another chance with the 1D X."
To top those findings, the new entry-level D3200 ($700) at 24MP has higher resolution than any of the Canon cameras. Canon is also said to be halting 5D Mk III shipments as it seeks to resolve light leak issue.
I must say that this is very disappointing for a Canon user. On the other hand, in the years before Nikon acknowledged FF, the pixel gap between Canon and Nikon was more than 1.5 in favor or Canon, and Nikons were useless at high ISO.
At this point, who would want to buy into Canon, unless they already have lots invested in the system, or they primarily shoot above 1600 ISO ?