How would you ever know if it was restored to match the print’s color, then? Even when people are able to match the scan to the print by looking at the projected print while they’re doing it, they are of course matching it to a specific bulb (hopefully the correct one). I mean, the print doesn’t even technically have color without a light source to see it. 😉 I think some bias is required because almost 0% of people are going to be watching it with the ‘correct’ type of bulb, even among the lower percentage of people who will be projecting it in some way. But the print itself doesn’t posses some ‘bulbless’ color state that is both objective and correct, does it?
Of course it does 😃. The “bulbless” color is when you shine white light through it. You should never bias a print during restoration. The bias is introduced when you shine a biased light through it, like a 70s bulb, which has a slight yellow bias. The colors are simply related to the respective amount of dyes, which in turn absorb, red, green light, producing the unbiased colors, if you use an unbiased light source. Now, if you’re interested in making a home video release that mimics a print projected with a 70s light bulb, you could incorporate this in your color grading, but if you’re color grading a print for projection, you definitely want the unbiased colors.