I’m looking for some recommendations based on everyone’s experiences, I’m really happy with the camera, just leaves something to be desired in the early mornings and evenings for most part I can get some reasonably good images I generally shoot wildlife, birds when the bigger mammals are not cooperating. This past weekend for instance I was after some elk pictures (I will post some when I get home tonight, before and after I ran through topaz denoise and some with sharpening). I’m running a ef 100-400 mk II I have a 1.4 III extender but very rarely use, my question for you guys is what is the best route to take with gaining a bit better early and late light performance and reduce having to crank up iso? Do I look for a used ef 400 2.8 or 4 (600mm wouldn’t be out of question either) and be able to also use the extender. Or do I jump to a r7 which will seem to give a bit better results from what I’ve gathered and use what I have with the adapter while gaining the better animal auto focus? I understand full frames are better for these scenarios but would 100% miss the reach of a crop sensor.
I haven't seen any convincing evidence that the RAW noise of the R7 is any better than the 90D; it is slight, at best. What is very different is the OOC JPEGs and default DPP conversions; they have more noise vs detail intelligence in their processing.
Regardless, the M6-II, 90D, R7, and R6 have very similar noise per unit of sensor area, and are Canon's top tier, and you can't really improve noise over the 90D without getting a lens with a larger pupil, and that would be true even if you switched to the R6, Canon's cleanest FF camera.
Now, many people *think* that the 90D is noisy per unit of sensor area, but they are ignoring the roles of magnification and gratuitous sharpening at the pixel level.