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So how does one utilize the HOT color space? There are several answers to this question, each with different degrees of expertise involved. If you are as skilled and equipped as Steve Lee (see his true HOT image), you can create spectrally correct HOT images by making CCD exposures through appropriate filters and combining them. You then need to find a way to properly display the result. If you are like me, you may be interested in seeing how existing images (including true HOT images) appear when interpreted as HOT-primary-based data. To do this requires an ICC color profile and a color management tool that can apply it. Photoshop 5 is such a tool. Photoshop 5.02 and above includes a mechanism to perform a "profile-to-profile" color conversion. This feature is found under the Image->Mode->Profile to Profile menu command. When you use this control, you are deliberately going outside of Photoshop's color management, essentially declaring that you know what you are doing. Even if you don't, this is all in the name of experimentation, so forge ahead anyway. The basic idea is that you want to pretend an image is based on HOT primaries. And you want to display it on a monitor that has non-HOT primaries, say sRGB (Trinitron phosphors). So to do so, you convert the image from HOT to sRGB. This process translates the digital representation so that the colors are preserved, even though the digital numbers that generate those colors are different between the two systems.
The "From" profile should be set to the HOT ICC profile, and the "To" profile should be set to sRGB (or the profile for your monitor, if different). The choices available are based on the profiles that Photoshop found (when it first started) in the system color folder that holds color profiles, so you may need to place a copy of the HOT profile there and restart Photoshop.
The other controls in the Profile-to-Profile dialog include the "Engine" and "Intent". These will make subtle differences in the result, but any of these choices will make a big change in the appearance of the image, because the two color spaces are so distinct. You should think of the result as being how the image "should have looked" if you were able to display the original on a proper display for it. Its original appearance should then be considered "all wrong" because it was being portrayed on a completely incorrect display. Perhaps this way of thinking is just my own idiosyncracy in trying to keep the color interpretations straight; you'll have to come up with your own way of tracking this manual color management. In my experiments with Photoshop's profile conversion tool, I found that it handled differences between these two color spaces in a rather unsatisfying way (to me). You may have noticed that there is a considerable range of colors that the HOT space can represent, but are outside of the colors that a monitor can make (see the HOT chromaticity diagram). This means that substitute colors need to be found to use instead, which is the function of another level of color management... gamut mapping. |
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