Author Topic: Aset, useful or a distraction to consumers?  (Read 14055 times)

Offline Diamondsbylauren

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Re: Aset, useful or a distraction to consumers?
« Reply #25 on: September 21, 2010, 09:10:30 PM »
Warning - if some of you get a sense of deja vu is because this was initially posted a couple of days ago, then got lost when David split this thread from the "Asscher" thread. Thanks to David's presence of mind, the post's contents were saved, and despite my reply being somewhat critical of David's position, he has invited me to re-post on this discussion. Double kudos to David for caring about potentially lost forum content, and more so for recovering it when it contains some disagreement.

So, here it goes...

Interesting OMC!
 
After using the aset to look at a lot of stones that I consider well cut, and some that I did not like, I came away feeling like the results were so mixed.
The image below is a perfect example.
Both stones are GIA triple EX. The one on the right shows much more distinct patterning.

But the use of ASET is not that of helping to identify patterns... or at least it's not only the symmetrical pattern that matters. Like Clgwli - and perhaps yourself - I like best slightly irregular cuts, and modern H&A leave me relatively cold. The ASET of the stone on the right does not interest me - it's a lot easier to tell from a standardised image than it is from two photos of perhaps two vendors using totally different lighting, photo techniques and post-processing.
 
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Yet, in real life there's no comparison where I'm concerned. The stones on the left sweeps me off my feel- the one on the right is nothing to sneeze at- but the non patterned stone flashes a lot more sparkle in my opinion.

Which is why entirely agree with you that an ASET (or indeed any other standardised viewing tool, such as a Brillancescope, ISEE2, IdealScope, or whatever other gizmo will be invented next) is useless to evaluate beauty. First of all because to a large extent beauty IS in the eye of the beholder, and secondly because to some extent even to the eye of the same beholder beauty is contextual. In a brand new piece of jewellery, scratches are not nice. Patina on a 30, 50, 100 year old piece can be, yet it's still scratches!
 
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But in terms of the quality of cut, according to GIA, both stones are equal.
There's the rub, for me.

I'm sorry, but I feel this is simplistic, particularly coming from you. There are good, nice eye-clean SI2 or I1 and very nasty ones. There are Fancy Yellows that are a lot closer to Intense than to Fancy Light and viceversa. There is surface graining leading to a "Good" polish grade, and there is sloppy(ish) polishing leading to the same grade. Even where one is not issuing a judgment on "beauty", you have always emphasised that a grade is a range, and it encompasses a variety of individual situations which can make the difference between a "good" and a "so-so" (or "bad") stone.
 
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It would be easy to make a case that the stone with the better aset is a better cut. If one wanted such a pattern, then the aset is useful.
But too many times the implication is that the better aset is the better cut.

Ah, but there are two "buts". First of all, AGS has not developed the ASET to detect arrow patterns or to assess optical symmetry in a stone, although it may help to do so. There is an H&A viewer to do that (not developed by AGS, although not dissimilar from an ASET in its operating principles - which incidentally are nothing new - darkfield illumination has been around by roughly 100 years, and ray tracing to assess diamond performance was used by Tolkowski in his 1919 book).
 
Secondly, there is no "better" ASET. There are two different ASET images and they tell me the same things about the stones. The distribution (% surface) of blue, green and red  is what I need to know to assess the likely amount of light reflected back into my eye, the presence or absence of contrast, and  the presence or absence of windows. Of course it also helps to assess the symmetry or otherwise of the pattern, but the judgement that the "symmetrical" ASET is the better one is yours, not mine. There is nothing anywhere that says I have to interpret the ASET in a certain way or that one image is better than the other. However, if you showed me an image of a round that is mostly blue, white or green - regardless of its symmetry - I would be cautious about approaching that particular stone. Can one say the same thing about a standard photo? No - there are plenty of "nice" images of crappy diamonds, taken using "tricksy" lighting.
 
And please don't give me any BS about your photos being "standard". There ain't nothing standard in those. To start with, they are truthful and unretouched. ;D
 
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And we're only talking about round diamonds.
Once we get to fancy shapes, it's even less useful to consumers.
There are stones with some dark areas- such as a bow tie- that aset does not identify.
And vice versa- times that the aset indicates potential dark zones where none exist in real life

The issue is that - if taken correctly, and thus under standardised conditions, including stone height and orientation - ASET images add information. Whether that information is easy to use, is another matter entirely. I can - to some extent - interpret ASET images of emerald and Asscher cuts as well as rounds; I cannot claim to have used it to any extent in other shapes. Interpret in the sense that I can form a pretty good idea of the manner in which contrast and reflection will play in the stone. Will it tell me "oh, this is a beauty"? No. Will it tell me "this is definitely best avoided"? Quite likely. With time (and enough exposure to ASET images and corresponding real stones)
 
Incidentally, I'd be quite interested to see a bow-tie under an ASET tool. If the stone is positioned correctly, the bow-tie should show as blue or white. I wonder though if the fact that the ASET sphere is round and bow-ties tend to show up in elongated shapes means that the reflection patterns are somehow distorted, and/or whether the fact that elongated shapes tend to be shallower than rounds... it would be interesting to test.
Thanks so much for reposting omc!
Let me clarify- GIA EX cut grade would include both stones, and many of the common aset interpretations of the two images will favor the more organized pattern.
People would make case that one stone was a better cut than the other, due to aset, and misinterpretation. That  aspect being "the rub".
I'm glad you bought up GIA, and it's grading system- which allows for human error, to some degree.
If the person submitting the stone really believes it's an F, and GIA gave it G, they can re-submit, sometimes GIA will change the grade.
There are numerical aspects to GIA cut grades (measurements) and subjective aspects ( polish and symmetry)
I would suggest even these aspects are less subjective than color or clarity.
The point is, I value GIA's cut grade. As a professional, I feel it's a fair statement to say that any diamond receiving GIA EX cut grade will be considered well cut by knowledgeable people.
There is a fairly wide range of acceptable measurements, meaning that there's a fairly wide range of outcome.
I am pointing to this to validate my point that there's a range of stones that can be considered "at the plateau" in terms of cut quality.

In fact, this is a key difference in the grading of cut, as compared to color or clarity.
Whereas the color/clarity scales are completely linear, the cut grade scale is more of a plateau, with drop offs at the edges.
And in some instances, the drop off is so very slight, as to be undetectable.
There's a lot of cases where people will prefer a given VG cut grade to a given EX cut grade due to proportioning.
This will include cases of stones downgraded for less than VG on Polish or Symmetry. In many cases the reasons for the downgrade take a microscope to see.
I like longer LGF's leading to more narrow "arrow shafts", for example. I have sen many cases where I prefer a stone given VG cut grade as compared to an "ideal cut" given EX cut grade.

There are sellers charging a premium for stones that are, supposedly, more strictly graded for cut than GIA's cut grade.
Or more accurately, stones selected to fit a certain taste within GIA cut grade.
The example of the two aset photos is perfect for demonstrating my point.


Here's a stone with a distinct bow tie


« Last Edit: September 21, 2010, 10:58:17 PM by Diamondsbylauren »
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Offline Diamondsbylauren

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Re: Aset, useful or a distraction to consumers?
« Reply #26 on: September 22, 2010, 06:00:42 PM »
Maybe the above marquise was not the best example.
It's not a very dark bowtie IRL
I'll search for another.
Meantime, here's the 1.20ct Faint Green
Another standardization problem may seem so simple- but it's not easy getting a diamond level on the platform to take the photo.
With a 1.00 round it's difficult.
With a 5ct Radiant, near impossible
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Offline oldmancoyote

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Re: Aset, useful or a distraction to consumers?
« Reply #27 on: September 22, 2010, 07:36:42 PM »
That really is an interesting cut. The table is so wide - but it doesn't seem to "damage" it. The relative shallowness and length of the lower girdle creates the "big culet" effect which one can see in the normal photo as well as in the ASET image. Is it as visible in real life, I wonder?

Offline Diamondsbylauren

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Re: Aset, useful or a distraction to consumers?
« Reply #28 on: September 23, 2010, 04:38:04 PM »
That really is an interesting cut. The table is so wide - but it doesn't seem to "damage" it. The relative shallowness and length of the lower girdle creates the "big culet" effect which one can see in the normal photo as well as in the ASET image. Is it as visible in real life, I wonder?

No- I can't see that circle in real life.
I took a few photos of the marquise, and have again revised my opinion- at least photographically, the marquise shows a black line running through it- which does not seem to translate into the aset.
There is certainly evidence of the line in the aset- but not as we see it in the photo.
« Last Edit: September 23, 2010, 04:38:55 PM by Diamondsbylauren »
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