Perhaps this is the first time I'm bringing up the
DiamCalc software results in this tutorial but we have been noting
correlations between DiamCalc results and visual observation for a
while now. Earlier last year (in 2005) when we did our review of the
GIA Cut Grading System we noted a direct correlation between the
various GIA Cut Grades and the Contrast metric in the DiamCalc
software. Results that can also be seen virtually through the
DiamCalc/Gem Advisor software "Office Lighting View". Below is a
demonstration of the comparison we'll be making with photography &
video except here are the DiamCalc results.
DiamCalc Metric | 1.89ct w/HCA >2 | 1.73ct w/HCA of 1.5 |
Office Lighting | ![]() |
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DiamCalc Cut Quality Results (note the lower "dark zone" score. This is the red flag we see which correlates to the AGS Contrast metric) |
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Note
when you compare the 1.89ct with the 1.73ct in the simulated "Office
Lighting" you can note more areas of darkness and less bright
reflections in the 1.73ct. Here are those graphics scaled down. for a
side by side comparison. The diamond on the left is what makes
GIA/AGS' top grade for Light Performance while the diamond on the right
fails in both systems for top optics (and for good reason we believe).
Here
is a photograph of the same 2 diamonds taken under the GIA DiamondDock
simulated diffuse daylight view. Can you pick out which diamond is
which based on the graphics above? I think it'll be easy for ya. ;)
The comparison of the DiamCalc Office Lighting View and the DiamondDock
simulated diffuse daylight view (live) we have found to have the
closest corelations when it comes to real world observations of the
optical characteristic of brightness. At least these have been my
observations.
Here's the same graphic blow up to show more detail.
To view a video comparison of these 2 diamonds under simulated diffuse daylight click here.
Note: While the shallow angled diamond above suffers in diffuse day
lighting environments (both simulated and natural) the diamond does
happen to excel in direct/spot lighting environments (exhibiting
fire/scintillation characteristics). In our professional opinion, for
a diamond to be considered as having top optics or Ideal/Excellent light performance it must excel not only in spot lighting but also natural day lighting as well.