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Imagine a display system that used the hydrogen-alpha emission line as its red primary, the oxygen-3 line for making green, and a filtered high-temperature, black-body radiator for blue. These are the colors generated by emission nebulas, emitted by hot stars, and reflected by reflection nebula. These are the "HOT" (Hydrogen-Oxygen-Thermal) primaries, which define the HOT color space. As an example, the pictures below are from the same digital image. The one on the left is a conventional rendering: its "color space" is specified by the Trinitron phosphors (the primaries in the sRGB standard). If you are viewing it on a Trinitron monitor, you are very likely seeing the same colors as I see, which was color-managed to be similar to the colors on the original E200 slide. The right hand image is a simulation of what it would
look like if it were rendered on a device (display or
printer) that uses the HOT primaries. |
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The most obvious difference is the brilliant red of the HOT rendering. This is still not true to the red we would see from the hydrogen emission line at 656 nm, but it is the best that your display can do! And one could argue (though I wouldn't) that it might be closer to what this bright emission nebula would actually look like if it could be seen at photopic light levels. There are more subtle differences in this picture as well; the blues are a little less violet, having moved closer to green due to the nearby influence of the O3 primary. A pure blue in this picture represents the color of an extremely hot star, as seen through the astronomer's photometric B filter, a good approximation to the sensitivity of film and also to the human visual system's blue response. Note that rendering an image in this way does NOT make it a calibrated image in any sense of the word. It is simply another way to interpret the encoding of color in a digital image. Instead of using the conventional primaries in film, scanners, and displays, we are using primary colors found in a different realm of Nature, the deep sky. Continue, for more information on the HOT color space, ICC color profiles for it, example images, and how to use Photoshop to convert images to it. Use these links or the "previous/next" links at the top of the page:
Some more general and clarifying topics: |
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