I just spent a bit of time experimenting with my 24-105 zoom lens and the 77mm polarising filter. I wanted to see how much it affected sharpness and brightness of the image when fitted, so I put the 400D on the (crappy, wobbly) tripod and took some test shots from the front verandah.
First discovery – although the lens is very sharp wide open (f/4) at 65mm if you stick with a UV filter, I needed to stop down slightly to preserve detail with the polariser on. So, both test shots are at f/5.6 and the same 65mm focal length.
Here’s the shot taken with a standard UV filter (aka the lens protector). The shutter speed was 1/640 sec.
And here’s the polarised shot. It was taken a couple of minutes after the previous shot, but the shutter speed dropped to 1/125 sec.
I think the polarised shot has much nicer colour, and it hasn’t lost detail (which you wouldn’t be able to see at this resolution, but I’ve compared both shots at 100% magnification). The tradeoff is a 500% slower shutter.
Obviously this filter is going to be a very situational thing with this lens. Perhaps I’ll have more leeway with the 70-200 f/2.8 lens? I think I’ll pick up a polariser for the 50mm lens and see how that copes.
