Jun 9, 2005

Understanding ProPhoto RGB – UPDATE

On May 27th, PSN reported that Michael Reichmann, publisher of the Luminous Landscape website, had written an article titled Understanding ProPhoto RGB A Preferred Working Space for Digital Photographers. The article was useful (read the original article on) but spawned a lengthy discussion of the relative merits and risks of using ProPhoto RGB in the Luminous Landscape Forums.

The discussion centered around the advisability of using ProPhoto RGB because it’s color gamut, the amount of colors contained, is so big. Read the original thread. Note, to post, you must register for the forums (free), but anybody can read the existing messages.

Several valid points were made regarding the risk of using ProPhoto RGB as a working space. First, it’s a really large color space. So large in fact that there is now way to actually SEE all the colors in real life, let alone on a computer display. Discussion also mentioned the potential for introducing banding-particularly if using an 8 bit/channel bit depth. Additionally, it was pointed out that delivering a file in ProPhoto RGB can be a problem if the recipient is clueless about color management-ProPhoto RGB files look pretty horrible when opened into sRGB for example.

However, the discussion also pointed out the usefulness of using ProPhoto RGB as a working space-particularly when opening raw images using Camera Raw. The advantage is that one weakness of ProPhoto RGB, its size, is also a real benefit when opening images using Camera Raw because ProPhoto RGB will effectively never clip any color data.

It was also pointed out that current and particularly the newer Ultrachrome K3 Epson ink jet printers have the ability to print colors that fall outside of even Adobe RGB (let alone sRGB). The fact that one can’t see all of the colors on a computer display is also mitigated when using Photoshop’s soft proofing capabilities to preview the results of outputting on larger gamut printers.

If you want to see a useful discussion, this thread does a pretty good job of covering most of the up & downsides of using ProPhoto RGB. We suggest you check it out.

4 Responses to “Understanding ProPhoto RGB – UPDATE”

  1. Glenn McLaughlin Says:

    I’ve noticed that even on a calibrated system with ColorSync
    prefs set to ProPhoto as RGB default in OS X that all system displays like file thumbnails and even the print with preview dialogue box, show Profoto files as distinctly greenish. Output is fine. Anybody know why?

  2. Andrew Rodney Says:

    Looking at 3D gamut maps of both custom profiles I built for the R800 and 2400 (gloss papers) indeed there are areas that fall outside Adobe RGB (1998). More on the 2400 than R800 but certainly a noticeable amount in yellows and some greens.

    The RGB defaults in ColorSync (which have been pulled from Tiger) are kind of flakey. You’re lead to believe this is used as a default for untagged docs (that’s what it says) but this doesn’t seem to be the case. Depending on what application you’re using, especially Apple Apps, this “default” is ignored and sRGB or your display profile (or Generic RGB) is being used. I’m frankly confused what Apple is trying to accomplish here in Panther but moving onto Tiger, this preference is gone.

  3. Glenn McLaughlin Says:

    Thanks Rodney.Just one of things that make you go hmmmmmm…
    with apple.

  4. Dmitry Kitsov Says:

    I have posted an analysis of a practical side of the issue on my blog:
    sorry for the shameless self promotion

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