Linear polarizers can only be stronger in effect if they are compared to a not-so-good circular polarizer.
Remember that the working bit is the same in both types.
So given a linear filter that has a 'strong' effect, using that same foil in a circular polarizer would produce the very same effect.
The retarder plate put behind the polarizer in circular polarizers will change nothing about what the polarizer in front of it has done. It cannot allow light through that did not make it through the polarizer in the first place.
Well, I am comparing different brands, however, I would think Hoya and Tiffen would both be good. In my case, the linear Tiffen seems to be better than the circular Hoya. This is just to my eye - not scientific.
Moma don't take my Kodachrome away!
Oops, Kodak, of all people, did!
The filter factor is fixed, and usually is 2x (1 stop). It will say on the rim of the filter.
Manual metering is the best way of metering when using polarizers.
As you say, the effect is variable. Depending on the light in the scene, and the orientation of the filter, light coming from parts of the scene is held back (selectively; other parts are not affected).
That is what you want to happen (else you shouldn't use the filter ), so you do not want to compensate for that.
What you do need to compensate for is the overall, non-selective blocking that also occurs. And that is what the fixed filter factor is for.
If you would meter through the filter, the meter will also register the darkening of the bits you want to have darker. The meter of course has no notion of selective filtering, and just registers less light. So the parts that are unaffected by the filtering will be overexposed (the amount by which depending on how much the filter 'does') if you follow what a meter behind the polarizer suggests.
So you're on the right track!
Mind you: images can look a bit dark, flat, when there is a lot for the filter to block.
You could adjust by giving it a bit more exposure. But it would often be better to just reduce the filter's effect.
Exposing a bit more will produce lighter images that are still rather flat, without sparkle. It's better to not remove all sparkle in the first place.
Last edited by Q.G.; 08-08-2009 at 09:55 AM. Click to view previous post history.