How accurate is machine grading

[canadian 1]

How accurate is machine grading? I was told that a G color diamond was graded by a machine so there would be no doubt in this area of grading.
Do machines grade any of the other C''s?

canadian 1

 

[oldminer]

Machine grading of the color of diamond is NOT accurate. Part of this is because color grading of diamonds was not created scientifically and there is issues with the way it is done as an accepted practice within the diamond trade. Diamonds are graded for color like no other material. The color is size related, not on an absolute scale....

The other problem is that machine diamond color graders have issues with trace elements and UV fluorescence. It causes them to err on occasion. Also, some of these devices can be "adjusted" by the user for legitimate or illegitimate purposes.

I have owned two Gran colorimeters and an Austron colorimeter and presently own a very costly spectrophotometer....While all four have merit, none of them is a bonafide substitute for master diamonds, correct lighting experience and good eyes.....

Sarin or Ogi devices can work with programming to grade aspects of the cut or of cut quality. This is what AGA and AGS does with measurements of various parameters.

Right now, clarity is not graded by machine although HRD uses some sort of scientific process in measuring the minimum size of reported inclusions. This will eventually happen here too, but when, no one could predict.

For brilliancy there are BrillianceScopes and the ISEE2 devices along with the simpler tools like the Ideal-Scope, which I am partial too. At least it is cheap, simple, portable and can't be "adjusted" at will.

Other "tools" such as H&A viewers tell us something, but really do not grade the stone. They are more geared to marketing.