If I have the lens correct then at 135mm the largest aperture is f4.5 and at 400mm its f5.6.
The polariser will cut the light by up to 2 stops so a/f will struggle as its equivalent to using a lens with max aperture of f8 or f11. If using at long range ( infinity ) the best bet is to use manual focus. Easy if your lens has a hard stop at infinity mark.
Don
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