John Sheehy wrote in post #18756918
As I explain later, stopping down may actually be
necessary for the same DOF; not an option.
Let's not get carried away. Most of any benefit you see in maximum R IQ at the higher ISOs is because you're using a larger sensor area, more pixels in that full image, and of course, you're getting more of the analog resolution of a given lens with the same f-ratio by using a greater percentage of its image circle. If you're viewing at 100% pixel view, you are viewing larger pixels at reduced magnification, an illusion of quality.
The generic benefits are the benefits of using a larger sensor
and using a shallower DOF, which isn't always wanted. When you need to stop down for DOF, the FF loses its analog optical advantage with a same-sharpness lens, because now diffraction is the limiting factor, and is the same at the image level with the same DOF and FOV. You now also need 2.56x the ISO on the FF for the same shutter speed. There's no escaping the fact that the generic FF benefit only comes with shallower DOF, when you need a certain shutter speed and are above base ISO. Comparing cameras with different sensor sizes at the same ISO is sometimes a purely academic exercise with no practical basis. The fact is, to do the same thing FOV-wise and DOF-wise, you do
not use the same ISO with different sensor sizes.
Then we have focal-length-limited photography. As soon as you start using less than the entire FF sensor area for your final composition, you forfeit its larger-sensor benefits (other than more flexibility in after-the-capture cropping). From all I've seen, a 1.6x crop from the R has less noise in the shadows at low ISOs (although the character is not as good as the 7D2's), but seems to have about the same noise at high ISOs, with greater resolution with the 7D2 and perhaps better noise character. I base this on the fact that DPR's studio comparison favors the 6D (similar to the 5D4) over the R at high ISOs, and I have the 6D, and do not prefer it over the 7D2 for focal-length limited photography at any ISO. I use the 6D only for shallow DOF and wide angle work.
Maybe instead of being glad about not having the 7D2 for ISO 12800, what you should really be glad about was that you were shooting with shallower DOF (made possible by the larger sensor)? Or perhaps you were viewing at 100%, with the illusion of greater subject sharpness and SNR, due to lower sensor area magnification?
I find it funny how there are always people talking about how much better B is than A, and how much better C is than B, and then how much better D is than C, and when you actually measure D vs A, the total difference is less than what was claimed for any one upgrade.
