I guess this is as good a time as any to ask this question that's always bugged me about sensor size and aperture.
I know the full frame sensor produces shallow DOF at higher apertures but I always assumed this meant that it also let in more light at these apertures as well. I have no idea if this is right, but if it is, wouldn't the 5D match the same light-sensitivity of an 0.95 lens on a M4/3ds sensor with a 1.4?
Btw, I too love the look the 12,800 iso hacked GH2. I intend to shoot a nightclub scene with it this weekend and I'm just thrilled at how unique it's going to look.
