Tim Munro wrote:
> ----- Original Message -----
> From: Mortimer Snerd <[EMAIL PROTECTED]>
> > Absolutely. The less light the autofocus sensors get,
> > the slower AF is. You lose about 1-2 stops from having
> > a polarizer on, so your lens will focus as if it's an
> > f4 or f5.6 300mm.
> I rang a contact at Canon CPS technical to get an answer. His reply was an
> emphatic no - the CP will not affect AF performance. He stated that it is
> not comparable to fitting a TC which slows AF down and is not a case of
> "less light" per se.
If I can weight in with my two cents worth:
With a CP on the front, you still have a f/2.8 lens. The size of the aperture
has not changed. There will be less light getting to the front of the lens, and
therefore to the AF sensors. But it would be more accurate to compare it to
shooting on a cloudy day (when the sun is 2 stops weaker), instead of full
sunlight. If your AF slows down on a cloudy day, I would expect it to with a
CP.
Personally, I don't use CPs much, and never on long lenses, but I haven't
noticed any slowing of AF when I do. At really low light levels AF is less
accurate, or tends to hunt more, but I haven't noticed problems in even cloudy
daylight.
Geoff Doane
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