2nd September 2002, 04:54 AM
Question about Polarizer Filters
Hi ppl, I've only recently learned that there are two kinds of them out there. The Circular kind and Linear. How can I tell if what I have is which just by looking at it? I got a Hoya one bought around 93 but it doesn't state which one it is. I used it with my manual system but now that I've switched to AF, I read that iit's better to use a Circular one.
Anybody care to shed some light on this? Thanks.
Last edited by Cleophas; 2nd September 2002 at 04:58 AM.
2nd September 2002, 05:19 AM
Here is an easy way to test whether a polarising filter is circular or linear:[list=1][*]Find a mirror.[*]Hold the polarising filter with the rear threads facing away from you, i.e. hold it "backwards".[*]Look through the polariser with one eye and observe the reflection of the polariser itself in the mirror.[*]If the reflection of the polariser (as seen through the polariser) is black/opaque (or nearly so), then it is a circular polariser. Confirm this by flipping the filter around and repeating the test; this time, the reflection of the polariser should be clear/translucent. The difference should be very obvious.[*]If the reflection of the polariser appears clear no matter which way you look through it, it is a linear polarising filter.[/list=1]Btw, if I'm not mistaken, all Hoya polarising filters will be marked specifically as "PL-CIR" if they are circular polarisers. Otherwise, it is probably a linear polariser.
It is true that a linear polariser may mess up the autofocus system of SLR cameras due to their beam splitter design, and circular polarisers are designed to overcome this limitation. If your polariser does turn out to be a linear one, try taking a few test shots using AF on subjects at various distances and see how the results are like.
2nd September 2002, 09:06 AM
i though the difference is between one can turn and the other is fixed?
2nd September 2002, 11:30 AM
2nd September 2002, 01:43 PM
Whao, thanks alot Midnight!! Now I can find out for sure. This forum is really helpful
4th September 2002, 11:56 PM
hmm all i noe is the cir. is for AF cam and the linear for non AF cam
and the latter is cheaper
but appearance wise, i duno how to tell them apart
5th September 2002, 05:02 AM
See my post above for the 'mirror test' to distinguish circular and linear polarising filters. Pretty cool when you try it out for the first time.
Originally posted by MaGixShOe
hmm all i noe is the cir. is for AF cam and the linear for non AF cam and the latter is cheaper but appearance wise, i duno how to tell them apart