I did find it odd that there was no discussion about whether those other media now represent the exact colors that they had when they were originally created. I know from experience that colors fade, but the argument seems to ignore that.

I also know that most of the old paintings that we have today have been though multiple rounds of "refreshment" in order to counter both the fading and dirt/soot that they were exposed to over the years (remember: most of these were displayed by torchlight/lamplight/candlelight for centuries). Nowadays there is a real emphasis on trying to produce an original ascetic, but that has not always been the case.

So I would want a better discussion of how accurate those "standard candles" are.