Silver dollar holder or what?

[Jay Ing]

So, I have my first big prime with a filter holder (Sigma 500/4, which I am digging)... but can't see any need for a polarizing filter for birding (1. PP can do that I think 2. Area needing polarizing changes so rapidly with birds 3. Loss of light)... so, does anyone use filters in their long lenses for birding or is this just a coin holder? :)

[Mike Hitchen]

I sometimes use a polarising filter if the bird is relatively stationary and if there is enough light, but it is unusual. I haven't yet used one for BIF because of the reduction in shutter speeds.

Nor have I used a coin in there - the hit on light is far too great.

[Doug West]

If the Sigma is like the drop-in filter of the Canon...I've never, ever have used anything but clear
filter. There's really no need to use anything else....but you definitely want the clear glass
filter in there.

Doug