Weird Results from Cokin Polarizer CP

[jhelms]

I use a Cokin P-Series filter system to alternate between a few of my lenses. Works great with ND and NDGrads, but this weekend I tried a Cokin Circular Polarizer with it and got really weird results.

It seemed to be difficult to get a blue sky with this filter, it almost defaulted to purple no matter how I turned it, and getting a pic with the correct looking white balance with this thing was like winning the lottery.

Back to back comparisons with my regular kit lens wearing a standard Quantaray screw-in CP, the same scenes looked fine. Maybe the QR CP gives me more play and the Cokin CP needs more finesse or something? Although I did play with the Cokin filter a LOT to try and get some better results.

Anyone else had this same problem come up?


Shot with 85mm 1.8 Nikon and Cokin CP with a 2-stop Cokin ND Grad in place also:

http://jhelms.smugmug.com/photos/522034793_CSDnu-M.jpg


Shot with 18-200VR kit lens and QR CP:

http://jhelms.smugmug.com/photos/522034526_tQYvJ-M.jpg

[pathfinder]

John,

In your first shot you used a circular polarizer, a 2 stop Cokin ND grad, and I think I see fill flash on the sunglasses as well. Is this correct?

Why all the filters?

If you are going to shoot with fill flash, shoot the camera in manual mode, and set the sky/background exposure whereever you want it - down 1-2 full stops from correct for ambient light, and let the flash in iTTL expose your subject for you correctly. Easy as pie. This will get you the dark sky and bright subject you are wanting, with no color changes either.

Using multiple pieces of glass in front of your lens is going to diminish the sharpness and contrast of your image, isn't it?

[jhelms]

John,

In your first shot you used a circular polarizer, a 2 stop Cokin ND grad, and I think I see fill flash on the sunglasses as well. Is this correct?

Why all the filters?

If you are going to shoot with fill flash, shoot the camera in manual mode, and set the sky/background exposure whereever you want it - down 1-2 full stops from correct for ambient light, and let the flash in iTTL expose your subject for you correctly. Easy as pie. This will get you the dark sky and bright subject you are wanting, with no color changes either.

Using multiple pieces of glass in front of your lens is going to diminish the sharpness and contrast of your image, isn't it?


Great point - and yep, you're right that's the setup I was using. But great point about exposing for the dark sky; sometimes I just can't think straight when I'm out there shooting and I come up with the most complex answer instead of the easier one :thumb

Here's the CP I was using on the Cokin:


http://jhelms.smugmug.com/photos/522811318_wy3FC-M.jpg

[pathfinder]

I agree, it does look like it has a funny magenta/grey color to it, rather than a strictly neutral gray color to a good B&W circular polarizer.