colorimeter accuracy

[gray hilsman]

Do colorimeter evaluations tend to be usually accurate,overstated or understated?
Thanks in advance!

 

[Rhino]

I've been using the Gran Colorimeter ever since they've been created. The 2nd and 3rd generation models have been pretty dead on most of the time. Once in a while I'll find a lab off a grade or so but it's usually within a half grade. We colorimeter check our stones along with masters.

Rhino