polarizing filter

[andycook]

What is the difference between PL (Linear Polarizing) and PL-CIR (Circular Polarizing) filters?

 

[gregr]

Circular is for autofocus lenses and linear is for manual focus lenses. That's the practical difference- as for the how and why of it... I dunno
Greg

 

[andycook]

Cool. Thanks.

 

[Wrench]

I, too, forget the reasoning but it has to do with the cameras internal metering system and AF. If you're shooting with a DSLR you'll need the Circular.

 

[andycook]

I am shooting with a DSLR. I found HOYA makes a polarizing filter/UV combo. Lots of choices.

 

[louist]

Almost all modern day SLR (not limited to DSLR) require circular polariser due to the design of the beam splitter (for metering and AF) and the mirror.

In practice, there are no differences between a circular and linear pol., they differ only in design. A cir. pol. has an extra filter after the initial linear polariser filter, this is called the birefringent layer, which converts the linear polarised light into a circularly polarised light.

 

[andycook]

Interesting.