Slains Castle

by pakman

submit your photo

Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Sign up ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

When I bought my polarizer, a friend told me that I should get a circular one, because the linear ones can mess with the autofocus. Is this true? What should each be used for?

share|improve this question

3 Answers 3

up vote 20 down vote accepted

A polarizer works in the way that it will let through only the light that is polarized in the same direction as the filter is currently turned. It is true that many AF systems have problems with this. To solve this, circular polarizer have a layer "inside" the polarizing filter that "un-polarizes" the polarized light so that the AF can function properly. The linear polarizer does not have this extra layer. The wikipedia article explains this quite well, I think.

As far as I know, there are no cases when you would want a linear polarizer instead of a circular one. Anywhere a linear polarizer will do the job, the circular one will work just as well, but not the other way around.

share|improve this answer
The inside layer doesn't unpolarize the light — it just polarizes it in a strange, non-intuitive way. – mattdm Mar 6 '11 at 15:43
The terminology used on photo sites is all messed up. What they call a "circular polarizer" is in fact a linear polarizer stacked with a circular polarizer. The second layer is not a de-polarizer as your post would suggest. – Szabolcs May 23 '14 at 13:46

Yes, it's true - sometimes. Some AF systems work OK with a linear polarizer under some or all conditions, and others fail all the time. You'd have to try it and see.

When would you want a linear polarizer?

  • They are often cheaper.
  • Since there's only one polarizing layer, not two, light transmission is often greater.
share|improve this answer

Because many AF and metering systems have problems with polarized light, circular polarizer has an added layer which "un-polarizes" the light that comes out. Therefore you should only get circular polarizers in usual cases.

The exception is when you want to use two polarizers to create a tunable ND filter. In that case, the front polarizer has to be linear, and then you can control the darkening effect by adjusting relative position of the two polarizers.

share|improve this answer
The inside layer doesn't unpolarize the light — it just polarizes it in a strange, non-intuitive way. – mattdm Mar 6 '11 at 15:44
@mattdm: So it like rotates polarization of the light? Because if it did another "round" of polarization, it would further reduce light transmission, wouldn't it? – che Mar 8 '11 at 10:03
yeah, there's a quarter-wave plate which transforms the polarization of the light wave into a sort of helix shape. It's not another filter layer, so there's no more light loss (other than the addition of more optics). – mattdm Mar 8 '11 at 12:46

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.