Help with evaluating images

[kev_b81]

I have been reading this forum for awhile and its been very educational.

However, I am not good at judging pictures of the diamond and the firescope. Can you guys help me out? This is a 1.1 ct, G, S1, AGS proportion Grade 0, round diamond. What do you think?

 

[Garry H (Cut Nut)]

Date: 9/29/2006 5:05:34 PM
Author:kev_b81
I have been reading this forum for awhile and its been very educational.

However, I am not good at judging pictures of the diamond and the firescope. Can you guys help me out? This is a 1.1 ct, G, S1, AGS proportion Grade 0, round diamond. What do you think?

Looks nice - I think it as ideal-scope and not a Firescope image though.
The stone was not sitting straigh in the tray- but should be a very bright looking diamond.

 

[He Scores]

Looks like my work....close to H&A but not like Paul''s Infinities. Looks like about an 875 or so BrayScore.


Bill Bray
Diamond Cutter

 

[JohnQuixote]

Maybe it is your work, Bill? It's a diamond we brought in for the client from an outside supplier.

I didn't know you could determine your score using the ideal-scope image (or are you using the 40X photo to arrive at it?) I'd like to hear more about this. Previously I thought you needed the diamond in-hand.

 

[He Scores]

John,
No I do not need the diamond in hand. To get an accurate score, I need the mfg. data from the Sarin machine uploaded to my websight.

HOWEVER, for those who have never TRIED BrayScores, you need only to look at several stones and you will be able to closely estimate the score based on previous experience.

I have my three stone test. I give someone three annonymous stones and written instructions to place the stones in the order of best to worst cut. Then they are asked to place a score on them from 0-1000.

It was uncanny how many people in the trade could come close to what the actual score was, but even more so was that the differences between the scores on the stones was even more accurately guessed!

I would post the pics of the three stones, but I''ll be darned if I know how.

Any help out there?

Bill Bray
Diamond Cutter and Inexperienced photo poster.

 

[pricescope]

Here are Bill's images. From left to right: 32, 33, 38.

 

[He Scores]

John,

So now can you see how I could guestimate on the score any particular stone would recieve?

The 32 on the left is a BrayScore of 628. What you can''t see in the pic is a very thick girdle. This was a machine cut production stone.

The one in the middle (33) is obviously the nicest. It was cut by a fellow diamond cutter friend of mine with instructions to go as nice of ideal (read Tolkowsky) and under 60% table. It has a BrayScore of 922.

The 38 stone was a stone that I cut. My friend and I each had identical pieces of rough to start with. Same weight, grain etc.
Mine came out with a BrayScore of 861.

My friend worked on his about his for several days and ended up with about 8% more weight loss than mine.

I worked on mine for about 2 hours and had an outside contractor(intentionally, so it would not come out exactly like my friends since we both learned to cut the same way) brilliandeer it.

At the time, none of us knew how to fashion the H&A.

2 of the 3 stones got an H&A comment from the PGS lab in Chicago, the 32 and the 33 stone.

In my survey, approximately 96% of the trades people were able to correctly identify the top two scoring stones.

Out of them, 54% correctly identified the highest scoring stone. (This is explained by the fact that the while the symetry on the 33 stone was better, the finish and "optical refraction" (graded by GCAL) was slightlly better on the 38.

The fact that only 54% could identify the highest score should not be shocking. To put it into context, the variation is similar to judging a flawless to a VV1 or a VV1 to a VV2. You might have a similar judgement error, IMHO.




Bill Bray
Diamond Cutter