Hi I needed to get my head around the dof issue. As far as I'm aware a full frame sensor like the 5d mkii doesn't actually give less DOF because l a lenses focal length doesn't change, whether you use it on a FF or cropped camera. It's just that you have to physically move closer to the subject with a FF so as to have the same field of view as a cropped camera. And when you move closer you naturally get less DOF. So that being the case when you use a FF camera you have to increase the the aperture, thus losing more light, and increasing the threat of diffraction. I know that FF camera operate better at high iso but if more DOF is required eg, macro or landscapes doesn't it make this a mute point. Please could you let me know if I'm right about this assumption or I'm barking up the wrong tree. Thanks.