Linear vs circular polarizers

Hello all

I'm not sure if this is the correct place to post this. (Wasn't there an “Accessories category “ that had filters as a topic listed?) If there is a better place to post this question, please advise me.

Here goes:

I have read numerous times that it makes no difference to the film / sensor whether a linear or circular polarizer is is used, yet I remember taking pictures in the '70s, & '80sw/ linear polarizers that showed skin tones & other tones to be much darker . It also seemed easier to tune the effect of linear polarizers than it is today w/ circular ones. I realize that the last sentence could be caused by reduced acuity of my eye sight and/ or the possibility of poorer quality of today's ground glass's screens. But the much grater contrast & darkness of of images of human skin had nothing to do my vision. Admittedly I had many more female friends who were happy to be photographed wearing bikinis than I do today:-(

I was using Kodachrome (the Kodachrome lab was ~ 5 mi north of me in Hollywood, very convenient) & other transparency films, but I also shot quite a bit of neg. color film & I remember them coming out contrastier too, although not as contrasty as the transparency film.

All this causes me to believe that linear polarizers, work better than circular ones. I doubt that I'm right abut this & every writer on this topic is wrong. Could someone please give me a plausible explanation of this for the confusion that I'm having?

Thank you, JD McGraw

Mod note: moved to "Accessories Forum"

Despite silly 'explanatory' diagrams to the contrary, there's no real difference in the polarising membrane used in linear or 'circular' polarising filters.

The difference is that a so-called circular polariser also has an element called a quarter-wave plate following the polarising membrane. This effectively de-polarises (or scrambles) the light again after passing through the polariser.

The reason for the introduction of circular polarisers, was that early AF and some TTL metering systems were made less or ineffective by the use of a linear polariser. De-polarising the light entering the camera made this less of an issue.

Personally, I've never found that using a linear polariser made the slightest difference to the AF or metering of my cameras (all Nikons), although I do own circular polarisers as well.

I've also not noticed any difference between results from circular or linear filters; that's apart from a lack of neutral colouring with some filters, but this applies equally to linear and circular types.

In short, there's no practical difference between polarising filter types in my experience. YMMV.

BTW, because of their construction, circular polarisers only work one way round. If you hold them to the lens, or to your eye, backwards there's no polarising effect.

FWIW, polarising filters (any type) can remove the 'sheen' from perspiring skin and from foliage and shiny materials in general. This often results in greater colour saturation in polarised shots than those taken without a filter. Conversely, the contrast of B&W shots can be greatly reduced by the removal of specular highlights. Foliage in landscapes can be made to look very flat through the use of a polariser.

I suspect any difference you saw was down to the difference in quality of polarizers you were using-some are just better than others.

BTW, I've always used circular polarizers because-aside from my first camera(a Canon A-1) most of my other cameras back in my early days needed circular for the meters to work correctly. Canon started using beam splitters for metering back in the 1960s. The only "good" linear polarizer I've ever owned was actually a recent purchase-it was a Hasselblad branded(made by B+W) polarizer in Bay 50 for direct use on my Hasselblad lenses.

Like rodeo-joe, in use I never worried about circular vs. linear polarizers, although there must surely be some places where it does make a difference.

I, too, have found that old linear polarizers to seem to have more effect than the circular ones, and that is not completely due to "quality" (brand, etc.)....

This conversation got me curious. I only have linear polarizers, so I ordered a circular polarizer to compare the two types. Both my linear and the newly ordered circular polarizer are Nikon brand, so my results will not have results biased because of differences in quality of the filters.

Don't hold your breath waiting for me to post results :rolleyes:, because I only shoot film and I don't digitize my photos. I may give a written report in a couple of weeks, though.

Hmm... Zzzzzzzzzzzzz...

http://bayouline.com/o2.gif

I gotta agree 100% with rodeo-joe.

I've always attributed people's different ratings of polarizers to different conditions of testing, and perhaps different expectations. But perhaps certain constructions degrade with age? I dunno.

If someone gave me two polarizers to complete, the first thing I'd do is to hold both up together, then rotate to see if they can black out the image completely. If so, I think this pretty much proves that both are good. (If either one is deficient, it will not be possible to block all of the light.) Note that the circular polarizer has to have the correct side towards the other polarizer. Note that nothing is perfect, but if the crossed polarizers get extremely dark, this should be plenty good.

In the real world, the polarization effect is only complete at one particular angle of light reflection (see "Brewster's angle). If one doesn't realize this it's easy to conclude that one polarizer is better than another because the shooting condition varied slightly. If you raise or lower the camera slightly, the effect can vary, depending on conditions. Best bet for on-camera comparison is to use a tripod, and finish the test before the light source can change.