SQUIRL033 wrote:
i use the Tamron 150-600 on a 7D Mk II, and often shoot BIFs in manual at 1/1000-1/1250, f/7.1 with auto ISO... many shots at ISO 1600-3200, they come out fine. the 5DIII handles high ISO even better than the 7DII, so similar settings should be no challenge at all for the 5DIII.
I appreciate your comment Squirl. I agree 5dm3 handles high ISO great. But every situation is different. In this particular situation ISO 2000 produced a lot of noise, which I had to work at reducing in post. On the flip side I have shot at ISO 8000 in decent light and had acceptable noise.