I have been running into an issue with a specific combo of body/lens/filter that I cannot figure out. 90D, Canon 70-200 L IS F/2.8, any brand CPL. When I run this setup, the AF lands about 2-3ft behind the subject. The moment the CPL comes off, AF is perfect. I've used this CPL on other lenses on this body with no issues. These filters on that lens on other bodies works perfect. It's just this combo. Lack of light shouldn't be the issue as the f stop doesn't change the outcome and I am shooting outside in bright daylight. I ideally want to use the CPL as my next big event is all around cars, so reducing glares would be a massive benefit. Looking for any help at all.
I seem to recall that sometime back in the 2007 - 2008 period I had a problem with a Circular Polarising Filter and my Canon 5D MkII/Lens combo. I cannot remember the specific details now, but I resolved it by purchasing a better quality CPL. However unlikely it may seem, it may just be that your specific camera/lens/CPF combo are incompatible. Is there a chance you could borrow another or better quality CPF just to try it out on that camera lens combo?
