Rapaport-article on the new AGS-system

[Paul-Antwerp]

Running around in Vegas, it is difficult to find the time to go online and check what happens on Pricescope.

Anyway, this is just to inform the homefront that we have not forgotten about you.

Here is a link to an article on the Rapaport-site regarding the new AGS cut-grading system: article

Read it carefully, because, even if it does not give you the nitty-gritty details, there is sufficient info to understand the basis of the new grading system and the philosophy behind it.

In the next weeks, you can expect me to write some articles on further details and on how to use and interpret certain new information.

Live long,

 

[JohnQuixote]

Definitions
• Brightness is the return of white light.
• Contrast caused by obscuration is the dark areas seen in a faceted diamond.
• Brilliance is brightness with positive contrast effects.
• Scintillation is the combination of white and colored sparkles seen as the gemstone and/or the observer and/or the light source(s) move. Dynamic contrast plus dynamic fire equals scintillation.
• Leakage is areas that do not return light.


Though a metric for scintillation is still to be fully developed, this is the most robust foundation we have seen. Contrast is a starting point for understanding overall scintillation, since contrast influences the sharp, on/off quality perceived as the stone moves through a range of tilt, as well as the prismatic effects of dispersion in a diamond.

As it has been previously described, a diamond''s contrast footprint may be thought of as one frame in the moving picture of scintillation. "Dynamic" contrast = contrast through movement. "Dynamic" fire = dispersion through movement. Modeling and observation of these elements will be key in development of a meaningful (finally) metric for human perception of scintillation.

 

[WinkHPD]

Spending time with Paul this week was a whirlwind adventure. He was constantly sharing his views and interpretations of the new AGS system with me and others and he was constantly in conversations with some of the most informed people in our industry, including of course Peter Yanzer, head of AGS.

Wink was often allowed to be the fly on the wall, listening and absorbing enourmous quantities of information. Early in the fist full day I was there Paul''s business associate Lieve (pronounced Leeva) told me of taking two stones around and being told by the men that they liked one stone better and by the women that they liked the other stone better.

Later in the day in a presentation at the AGS Laboratory to a small group of appraisers taking a class there Peter Yanser talked about obscuration angles from 30 degrees to 40 degrees. It turns out that a stone cut to proform best with a 30 degree obscuration angle looked better to the men while the larger hairdos of the women blocked too much light for these stones, and that the stones cut for the 40 degree obscuration angle did not have enough contrast for the men, leaving the stones to look not as "lively" to them as the stones with the smaller obscuration angle. (Obscuration is the light blocked by the head of the observer.)

There was a lot of discussion about contrast at the presentation and a big AH HA was felt by me when I realized the answere to Lieve''s question of why men and women tended to like different stones differently. I am betting that stones cut for a 35 degree obscuration angle will be well liked by both. It was but one of the AH HA moments at this conference.

Wink

 

[Paul-Antwerp]

Hey Wink,

Interesting idea about the hairdo. Although, in Lieve''s case, her hairstyle would take her to the other category.

By the way, we missed you here yesterday.

Live long,

 

[WinkHPD]

Yes, but she did not say that she liked one stone or the other better, only that the men and women she showed it to did. Maybe she did say it and I did not hear it, I am not the perfect fly on the wall, only a fairly good one.

I appreciate your comment, but I think you were too busy to miss me much! I see that you met Brian the Cutter and the lovely Lesley. I hope it was a fun meeting.

When do you return to Antwerp? I need more of the Princess cuts. Go HOME, NOW!

Wink