[prof55]

Harp: No intent to confront in my request, and my apologies if it appeared so. I was merely interested in your conversion method. If I seemed a bit blunt, I expect it was my reaction to being told by mech that a lot of my previous work was "in error", and in his later unwillingness to elaborate on his statement without "proof" of my knowledge.

Regardless, the issue of D65 vs C is an interesting one. As you say, "the D series of illuminants are constructed to represent natural daylight. They are difficult to produce artificially, but are easy to characterize mathematically." It is for this very reason that color measurement instruments seldom use an actual D65 source; rather, they measure at another temperature and convert mathematically to D65, returning results in L*a*b* or other color spaces.

Further conversion is necessary if RGB results are desired, and this is where it gets interesting. Your use of the Lindbloom calculator is a good choice in my opinion, but there are others that will give varied results. Some calculators are not particularly useful for conversion between color spaces; unfortunately, EasyRGB falls into this classification. I arrived at this conclusion after extensive conversation with the author of this program, and perhaps this shortcoming is what mech makes reference to (though he seems to lack any actual facts on the topic). Any error in my previous figures has long since been corrected, and thoroughly explained.

More importantly, one must also bear in mind that RGB represents only three points on a spectral curve, and these points may not coincide with the RGB of the actual projector used. It is quite possible to concoct a mix with a perfect RGB that is unusable as a screen. This is why I have encouraged the use of spectral curves over RGB, a practice I am happy to see is being continued here.

Garry