I just read about the pro photo RGB color space advantages. I tried to use it in P/S but could not find it as a working space. Where do I get it?

Make sure you click on "Show More Options" in the color management box. Once you do, ProPhoto ill become available as a choice.

Yes that did the trick. Now, I have a canon 1d mk2. What color space would you say to be the best to use in the camera.

Editing spaces are chosen based on your needs in post production and not the type of camera yo have. Every camera captures more colors than what appear in smaller spaces when shooting raw and thus all can take advantage of ProPhoto.

I use ProPhoto due to it's large size which affords me the most flexibility in color adjustments and output conversion.

If you search the forums, you should be able to come across a thread that discuses ProPhoto in more detail.

Yes, if you shoot in RAW, and bring a shot into Photoshop using ACR under ProPhoto, you will get access to the full range of color detail produced by your camera. But your display or output devices may have much smaller gamuts than the ProPhoto space.

I think that may be why some people avoid the wide gamut editing spaces. Since they can't see any difference on the monitor (or even with printed output, unless all the correct color managed details are handled correctly), they assume there's no benefit. But if you watch color numbers carefully for specific pixels while editing, you can see huge differences in the ability to make subtle corrections. In my opinion, this is one of the major advantages of RAW capture.

Wes