Doug Harvey wrote:
Interestingly enough, when I first tried to use a polarizer with digital, I didn't get what I was expecting, but fixed all that...Now, I just a neutral density and everything is fine..Unless you are looking for dramatic effects, then I'll break out the B&W filters...

Really?  Film filters work on digital just fine.  There maybe sensor blooming issues with certain film filters but not Polarizers.

Todd Steinwart wrote:
I'm not a fan of filter f/x, but:

There are some fractured light Cokin filters (kaleidescope, etc.) that would be difficult to reproduce in PS.

If you want to do a whole set with certain f/x, it's much faster to modify the input than make the same change to a lot of images in PS.

The original poster asked about a simple blue filter.  This is easily don't in PS without 3rd party plug-ins.

properlyexposed wrote:
The original poster asked about a simple blue filter.  This is easily don't in PS without 3rd party plug-ins.

Blue polarizer to be exact. Blue filter yes, but polarization isn't something I've seen done properly by any 3rd party PS filter.

About the Cokin blue polarizer: It's not a circular polarizer so it will probably screw up autofocus. As another poster mentioned, you'll need to set your white balance before adding the filter, otherwise AWB will neutralize the blue aspect.

My rec: get a good glass circular polarizer (Hoya or B+W) and add the blue in post.