I am having difficultiy taking basketball sports photos with my Canon EOS 90 D in AI Servo and high speed continuous shooting. It will focus for a few shots and then becomes blurry. I tried turning off facial recognition but that did not help. My aperture is 2.8 and 1/1600. Will welcome any suggestions. I love the camera, but am frustrated. The lens is a Tamron 70-200.
Take the time to do a deep dive into how the AF system works. If you have not already downloaded the “Supplemental Information” User Guide for the 90D, then I strongly encourage you to do so. For whatever set of reasons, information about the AF system was not included in the initial release of the full User Guide. So, Canon released the second guide.
Unlike factory default behavior for One Shot AF, the camera does not wait for an AF lock before firing the shutter in AI Servo mode. This is done to improve sustained frame rates. This behavior can be changed in the AF menus with the Image Priority settings.
Try setting 2nd Image Priority to “Focus”, which may slow down the frame rate during extended bursts of continuous shooting.
You did not mention which AF Point(s) you are using. Experienced users prefer to use just the center AF point. This requires practice to be successful. It places the burden of tracking subjects on the photographer because you MUST keep that single AF point on the subject.
I recommend using 9-pt Zone AF for new users. It allows you to use the same Center AF point, but offers the benefit of using the surrounding AF points to keep an AF lock on your subject when the center AF point slides off the subject. The photographer is still responsible for subject tracking, but Zone AF is a little more forgiving that using a single AF point.
First thing to do is turn off Ai-servo. Your 90D doesn't know what you want in focus so it jumps around. Use One shot and just the center focus point. Put that single point where you want it. In low light it is often the choice of a more wide open aperture. That brings its own challenges with very limited DOF. Kick the ISO to bring down the f-stop values. Lower the SS too.
At the very top of the list of photography requirements for sports is KNOW THE SPORT. If you don't know what's going on or what is about to happen you will always struggle getting good shots. Second most important is where you shoot from. Confined to the bleachers adds its own challenges so great shots are even more difficult.
This is just my preferred settings which may or may not work in your gym. Av mode, camera sets SS, Auto ISO with lower and upper limits set in camera (perhaps 200-6400). Average WB which isn't important since I use Raw file format and you should too. Post edit in a good editor like DPP (free) or Photoshop.
But I can't stress enough the first two, know the sport and location from where you shoot. Ignore these and good luck getting good shots!