I've been considering adding a prime lens to my zooms (70-200 F/2.8 IS & 24-70mm F/2.8 both MK I) because I'm increasingly frustrated with the problem of needing full ISO (3200 on 1D3) and not quite fast enough shutter speed to capture sport - namely karate tournament where I cannot use flash, and need a lot of to post-process to get anything like reasonable exposure.
I'm thankfully allowed quite close to the competitors, and have been through a lot of shots to see that usual focal length is around 80mm so I'm considering adding a second-hand 85mm F/1.2 L
Given my budget won't allow upgrading the camera anytime soon, I was thinking an 85mm would do the job, but wonder if the focus speed is similar to (or better) than the zooms I already have.
Any thoughts? does anyone out there use an 85mm for quite fast action sports in low light care to comment?