I have the Sigma C 150-600 on a d7200. I'm mostly using bbf with single point. I pretty much use single point for everything now. I play with 39 point sometimes for birds in flight. Sometimes I forget and I leave it on 39 point for birds on the ground or trees. Its not good. It will either miss focus or it might not even try. That's actually a good thing when it doesn't even try because I know immediately to set it back to single point. Also be sure to turn off OS when using a tripod. It is a 'must' with this lens.
focus focus focus - give up
- Thread starter Hobbit
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Woody, the way I understand it, if the contrast and overall tone of where the point was placed is very similar to the surroundings, the camera can't tell the difference. If the background is overly bright or dark, then it is easier for the camera to stay on the subject. At least that is how I've understood the concept when more than one point is used. Maybe I'm wrong though....
You are right that dynamic focusing is not perfect and can get fooled at times. With moving subjects, though, I will take that over single point every time. Better yet in many situations is group autofocus, but that's not available on many of the Nikon DSLRs. Just my two cents worth.