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Colour grading


G’day; First let me thank all those who enlightened me on the subject
of professional colour grading.

I thought that when I started the ‘hare’ of scientific numerically
based gem grading, that something would have been done by now. I
took my gemmology course around 30 years ago and would have thought
that someone might have come up with something on the lines of a
little diffraction grating spectrograph which could be plugged into a
computer and a specialist program to sort things out. In this
’enlightened’ millennium standard light sources and backgrounds are no
problem. 60 years ago, I was used to using a pad of finely ground
magnesium oxide as a standard white background. But from the replies
I have seen, seems 'taint so. I can see how not only the sparkle
from facets would confuse instruments, but that prismatic refraction
would play havoc, giving spurious rainbow readings. But although one
bloke suggested using ground glass screens to average things out,
surely rotating the gemstone at say, over 1000 rpm would do any
averaging? If one adds all the colours in a spectrum at the strengths
a facet provides, one ends with white. Trouble is, I am always a
trifle sceptical of based upon what one human perceives,
against the opinion of another.

I suspect the problem is that there is much more money in doing all
that work on something more consumer oriented, so why bother with a
thing which most jewellers can’t afford?

Anyway, thanks for all your input. Cheers, – John Burgess;
@John_Burgess2 of Mapua Nelson NZ