Polarizer and IR Filter

[Ranger187]

I have the PRO1 and I'm looking for a 58MM Polarizer (I plan to use them on the 20D). Then after looking noticed there are a few different types of Polarizer and IR filters.

I plan on getting a Hoya Filter, but I dont' want to get one and then find out, "Man, you should have gotten this one" that's quite annoying... And I don't like to throw money away.

And for the IR filter, I just want the standard black / white type #89B (R72) <--- That looks to be the correct one, and the most common. Am I correct?

Below is a picture I took recently in a Cave testing some settings before I go back to take more....

I'm looking to reduce the "hot spots" of the lights. Do I just need a standard Hoya Polarizer and that's it? I noticed they have:

1. Standard
2. HMC
3. Ultra
4. S-HMC

Should I be going for the SHMC?

http://www.harhigh.com/gallery/february_2005/iec/CRW_2541.jpg

[Jon]

You want at least the HMC multi-coated filter, to minimize reflections and light loss. I seriously doubt that you'll be able to polarize the bright spots out - they all appear to be from the cave lighting, and a polarizer won't do much for a direct light source.

Yes, an 89B/Hoya R72 is the correct filter for IR, but expect l-o-o-n-n-n-g exposures. Tou've probably already got an IR-screening (blocking) filter in your camera.

[Ranger187]

So how do I correct those bright spots then? Those just ruin the pictures and I don't want them....

[Jon]

Either very careful framing to screen them as much as possible, or by doing some PhotoShop work. If these are fixed lights, you'll have to live with them. If the owners of the cave will permit, you may be able to put some polarizing material over the lights and use a polarizer on the lens to cut down the intensity, but that's also going to seriously impact the available light for photography. If they're movable, you'll have to be careful where you set them up.

[Ranger187]

I have free reign of the cave. But moving the lights is not one of them. I will get fined $20,000 per rock touched on any "live" wet rock... So I don't think that is an option. ;)

I was under the impression a Polarizer filter on the camera would cut this down. How would I go about correcting in Photoshop?

[Jon]

A polarizer will only cut down reflections. As you're dealing with irregular surfaces and included light sources, there's not a lot of polarized light to deal with. In PhotoShop, you could make a negative mask and gradually thin it to allow the darker areas to show through while holding back the brighter ones.