Jeff USN Photog 72-76 wrote in post #19391048
for people using Animal AF here is another example from my 90D, this was not on 1 point but on 9 point, trees were at 100 yards, duck was probably about at 80 yards so it is a small target against a bad background. How do the R5 R6 and R3 handle this, especially the R3?
Am I hoping for too much? but this is my usual background for the most part and as I said I am going to rent and try it real life.
The R5/R6 recognize objects and tracks those objects. The phase detect AF board on the 90D cannot do this, for multiple reasons. However, in Liveview, you should have face/object tracking (called iTR) that might be able to follow that bird for you better than you trying to in the viewfinder. Different AF system entirely in liveview... (sensor is the AF system, not the separate PDAF AF board elsewhere in the camera).
You are fighting multiple issues here.
1) Distance (and thus size) of the bird you want to track. The larger you can get that bird into the frame either with a longer lens or use of TCs, the better.
2) The dark and busy background... that is going to cause some shifting of AF to that from time to time if you cannot track the bird manually with a set AF point, or if the camera is set up to try to locate objects for you.
3) PDAF system is vastly different on the DSLRs than the sensor based PDAF or contract detect AF. Mirrorless expands on the the sensor based AF model, with better AF algorithms and speeds than with DSLRs, other than the 1DX3 which has basically the same "mirrorless" solution in Liveview as the R6.
4) The smaller the object, the more you are digitally zooming into the bird after the fact, and the right camera with the right lens to be able to do that to still keep good detail and a decent version of the bird will be quite expensive. This is due to need of resolution, lower AA filter strength, and a very good high resolving lens.
5) With those kinds of distances, almost every single time you are fighting atmospheric distortion, and there isn't anything you can do to combat that other to get closer (reduce the space for convection currents to ruin the scene). So even if the R7 is the absolute best camera ever, and you put a 500mm or 600mm big white on that camera, your results will still be soft due to this, so you cannot throw money at this factor, short of buying a boat and getting closer to all the wildlife.
Points 1, 4 and 5 are all related to each other from different perspectives.