GCAL Light Performance Diagram: Meaningful? Or Meaningless?

[Smith1942]

While Blue Nile can't get ASET images of the stones I'm interested in for my potential stud upgrade, they have offered to send them to GCAL and get a report on them.

My question: How meaningful is the light performance diagram on the GCAL report? The key question: Is it as good as an ASET image? Not sure whether to bother with this or not. I have no idea about light diagrams and what they mean.

Here's a link to a random diamond and its GCAL report. How much can we tell from this? It doesn't seem as good as an ASET, but I wouldn't know. If it's not going to tell me a whole lot, I won't bother asking BN to do it.

http://www.bluenile.com/certs/220790050.pdf?params=cHJvZHVjdD1CTiZwaG9uZT04ODgtNTY1LTc2NDEmbGluaz1odHRwJTNBJTJGJTJGd3d3LmJsdWVuaWxlLmNvbSUyRl9MRDAyNTA0MDgzJnNrdT1MRDAyNTA0MDgzJmxhYj1nY2FsJnNpemU9MTYwMCZjdXJyZW5jeT1VU0Qm

Thanks!

 

[denverappraiser]

Re: GCAL Light Performance Diagram: Meaningful? Or Meaningle

The burden is on GCAL and the dealer to convince you that their data (or any other data they provide) has merit and, if so, how should you use it. The default answer is no. It's the same with any such technology. ASET is decently well explained on the AGS website for people to look but it's the same issue. It's up to AGS and/or the merchant to convince you that there's value to the information they are providing. If they do, consider what they have to say within the context of whatever credibility you decide you want to give them but the default answer is no.

 

[Smith1942]

Re: GCAL Light Performance Diagram: Meaningful? Or Meaningle

Thanks for the quick reply. So I shouldn't ask Blue Nile to do it, because it won't really tell me anything? This is for a pair of ideal-category stones which appear to have signature-ideal specs; however due to the 41 degree pav angle they seem to just miss the Signature category. I'm curious to see if I can get stones which perform to Signature standards without paying the Sig premium. Here are the numbers. I'm concerned about potential leakage and since this is an upgrade it would be difficult to exchange (I'd have to lose the cost of the setting.) This pair is $2856 and I have a credit for the old studs of $1411. Even with the price rises of 2011, this seems like quite a good price?

Edit: They are both D colour Si2 and BN has confirmed they are eyeclean. Yes, it's odd to get Ds but this pair is right at the threshold of the minimum spend to get my upgrade, so the lower colours were actually in more expensive pairs. I own a D pendant and I adore its extra-icy look.


Diamond 1
Cert: GIA
Shape: Round
Carat: 0.56
Depth %: 61.8
Table %: 56
Crown Angle: 34.5
Pavilion Angle: 41.0
Polish: Excellent
Symmetry: Excellent
Girdle: Medium
Culet: None
Size: 5.28 x 5.33 x 3.28 mm
HCA Score: 1.8

Diamond 2:
Cert: GIA
Shape: Round
Carat: 0.56
Depth %: 61.4
Table %: 57
Crown Angle: 34.0
Pavilion Angle: 41.0
Polish: Excellent
Symmetry: Excellent
Girdle: Medium
Culet: None
Size: 5.29 x 5.32 x 3.26 mm
HCA Score: 1.4





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[denverappraiser]

Re: GCAL Light Performance Diagram: Meaningful? Or Meaningle

Thanks for the quick reply. So I shouldn't ask Blue Nile to do it, because it won't really tell me anything? -

By all means ask them, and if they don't tell you anything useful, the fact that they don't have anything to say is part of the answer. Use that information as you wish.

FWIW, I have great respect for GCAL and have several friends who work there. It's a fine lab and a good company. I'm not holding them or their dealers to a standard that I don't put up for any other lab, including my own. The onus is on THEM to persuade you that their opinions have merit and that what they have to say is useful to you.

 

[Smith1942]

Re: GCAL Light Performance Diagram: Meaningful? Or Meaningle

Thanks, I've asked them to do the GCAL grading. From doing some research I knew they were a good lab. I just don't know how to read light performance diagrams, not being an expert! But it will be better than nothing, I'm sure. Perhaps it will put the light leakage question to rest. What do you think of the numbers, Denverappraiser?