Circular polarizer question

[karibethn]

I love this place. Edutainment! And it's all free!

[TexasTrails]

When using a SWA lens such as a 10-20mm, I use a GND filter inserted into a Hoya filter adapter to avoid the strange effects of the wide angle and CPL combination, especially if shooting wide open.

[kenmyers70]

jeesh, you had to bring us back to the topic.

So, how do you orient the GND to counteract unwanted CP effects?

[kenw]

would "seem" (no exact experience here, obviouosly) that a GND +CPL would still have the issue of variation of polarization, the GND would just darken it more.

ie; the non-uniformity of polarization would still be there.

topic? what topic?

[Jim Victory]

I'm sorry I had to go eat did I miss something?

[kenmyers70]

Nope. Just this Physicist geeking out and the Capt steering the ship off course. There is nothing to see here. Please move along...

[amature]

Originally Posted by kenmyers70

Do you think the OP cares about this thread anymore?

Actually I have been reading all of the posts again. I find all of this discussion very interesting. One can learn so much from the experts on this site. Thanks again for all the info. Much appreciated.

[LarrySmith]

Referring to wide angle lenses ... the wide angle lens sees a lot of sky and the sky varies in its degree of blueness based on where the sun is. Therefore, you will not be able to get even polarization of the sky with such a wide view. Go outside on a clear cloudless day and look at the sky from east to west and you will see what I am talking about.

Also, at altitude the sky is darker blue that at lower altitudes so care must be taken so you don't over polarize the sky or it will turn almost black.

Another use for a polarizer is as a variable neutral density filter from 1 - 2 stops depending on your particular CP. At minimum effect you proably lose 1 stop just having it on the lens. At maximum effect you may lose 1.5 - 2 stops. This can be handy if you need a slower shutter speed such as to capture motion.

The cool thing about a polarizer is you can see the effect before you screw it onto the lens. If you like what you see, add it to the lens. If you don't get the desired effect, check the location of the sun and determine if you can return later and get the image you visualize in your mind.

Larry