I learned about a Live View vignetting problem with the Canon 5D Mark II from several readers pointing me at a discussion forum at fredmiranda.com.
I have investigated with my own 5D Mark II, and I’m disappointed to report that the problem is indeed present, serious, and affects the three lenses I’ve tried so far. I hadn’t seen it because I rarely make my exposures in Live View mode; I switch out of it first.
There are white balance issues as well. My full report is in DAP, which also comments on how the feature exacerbates the problem.
It does not affect the Canon EOS 1Ds Mark III and does not appear to affect any “chipped” lenses, including the Zeiss ZE 50/1.4 Planar, only lenses used with a lens adapter (Leica, Nikon, Olympus, Zeiss). Furthermore, it does not affect normal exposures—only those in Live View mode. This leaves hope for a software fix.
As I said in November 2007, “Canon does it first, Nikon does it right”. This is yet another glaring problem for Canon to fix, following closely on the heels of the “black dot” problem and the 1D Mark III focusing fiasco (sub-mirror fix). Perhaps Nikon users hoping for 24 megapixels in a D700x should count their blessings.
Of course, Canon users do enjoy the ability to mount Nikon, Leica, Contax, Olympus lenses using adapters, something Nikon user do not enjoy without modifying lenses, so perhaps the issue is a wash from a brand perspective, since there is a workaround (using Live View for focus but not exposure).