[jstillion]

I've been trying to figure out if my Pentax *ist DL need a Linear or Circular Polarizer?
From what I've read, if the metering is split beam, I need Circular, older, Linear.

I've checked the manual / online and uses a (3 point) SAFOX VIII AF system but not sure if that's split beam.

With manual focusing, I assume it doesn't matter which type it would be.
(ex m42 ring adapter to PK)

[Imageman]

Circular

[patrick9]

I use a circular on mine.

[promacjoe]

It is recommended that you use a circular polarizer on all autofocus cameras, Regardless of whether you're using a manual focus lens are not. The reason is that part of the focusing system is being used regardless of the lens type you're using, that little light that comes on in your viewfinder proves it. However there are some Pentax cameras that do not seem to be affected by the type of Polarizer that you use.

A good way of checking to see if you have a good circular polarizer, Is to hold it in front of your monitor, object side toward the monitor and turn 90° back and forth. It should go almost completely black To transparent. If you flip it around so that the object side is pointing toward you, There should be no affect when turning 90°. This only works with LCD monitors. Tube type monitors will not have any affect on the view through the polarizer.

A standard polarizer will have the same effect regardless of which side you look through.

A bad circular polarizer will also have a similar affect regardless of which side you look through, it also may have a slight color change while you rotate it.

Stay safe and have fun.

Joe.

[jstillion]

It is recommended that you use a circular polarizer on all autofocus cameras, Regardless of whether you're using a manual focus lens are not. The reason is that part of the focusing system is being used regardless of the lens type you're using, that little light that comes on in your viewfinder proves it. However there are some Pentax cameras that do not seem to be affected by the type of Polarizer that you use.

A good way of checking to see if you have a good circular polarizer, Is to hold it in front of your monitor, object side toward the monitor and turn 90° back and forth. It should go almost completely black To transparent. If you flip it around so that the object side is pointing toward you, There should be no affect when turning 90°. This only works with LCD monitors. Tube type monitors will not have any affect on the view through the polarizer.

A standard polarizer will have the same effect regardless of which side you look through.

A bad circular polarizer will also have a similar affect regardless of which side you look through, it also may have a slight color change while you rotate it.

Stay safe and have fun.

Joe.

Thank You for that info, that's a great way to test the filter.
I knew some filters were poor quality filters, and not sure of a way to test them other then looking at user reviews.