Hi Stuart, > > My assumption is the following: As in photography > > we talk about filters, the circular polariser is in fact > > a circular polarisation filter - filtering out circular > > polarised light rather than letting it pass. Therefor > > a photographic circular polarisation filter would > > physically be a linear polariser. Anything else > > wouldn't make sense - physically speaking that is ;-)
> Circular polarizer filters are linear polarizers plus > an additional 'filter' to depolarize the light. The second > filter means that the camera's exposure and AF work :) Okay, this explains why a "circular polariser" works the same as a linear polariser but in one direction only! The secondary layer renders the polarised light into a more or less natural distribution. This way the camera-internal polarisers cannot black out the picture (for AF and metering) when positioned at 90' to the first polariser... This extra layer of "rendering" stuff is expensive and explains the extra costs over a normal polariser. > See http://www.geocities.com/cokinfiltersystem/polarizer.htm > for more details. Thanks, this explains my observations :) I love to figure out how stuff works. If you read the information closely, the name "circular polariser" appears to be a commercial one then! Physically speaking there is no circular polarisation envolved whatsoever! Rendering linear polariser would be more appropriate, but which self respecting photographer would buy anything with the word "rendering" in it ;-? This still leaves my second question regarding the Hoya Pro 1 Circ Pol unanswered: How are your experiences with this polariser on wider angle zooms (24-70 f/2.8 L and 16-35 f/2.8 L)? Is there any vignetting, glare etc? Cheers, Stefan * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
