I have a doubt about the effect of putting a filter (polarizer, UV etc) on the autofocus system.
In theory, a lens which is put in front of the lens will affect the focus (we must set a different focus setting in order to keep in focus the same subject, with respect to the situation without the filter).
My question is: does the autofocus system looks at the subject through the lenses, and so is able to keep the subject in focus even with the filter?