Misleading IdealScopes??

[teobdl]

Kenny often posts the very helpful 2 step process for selecting rounds:

1) Choose a few diamonds with HCA < 2
2) Select the diamond with the best IdealScope (with the help of PSers)

I'm wondering if someone with real life IdealScope experience could comment on circumstances in which an IS image that showed leakage and has an HCA >2 is actually a more attractive diamond than an IS that shows no leakage and has an HCA <2 .

How could this be the case? Is there a rule/set of circumstances that might predict when a diamond with a great IS and HCA < 2 isn't preferable?

 

[GoSounders]

Short answer: Everyone's eyes are different, and no tool encompasses everyone's visual taste.

Long answer:
I suppose you're asking because of the other thread where an inferior HCA and IS led to a better-looking stone. No tool used here will tell you definitively whether one stone is better than another. The tools only narrow it down to safer bets.

The HCA tool doesn't have a single "ideal" measurement, but rather judges how the measurements work together to create a well-cut stone. Low-HCA stones generally perform better than High-HCA stones, but there are exceptions.

Idealscopes measure light return, but not the method of return. A stone with a great IS may suffer in fire and scintillation. If a stone has been dug around the girdle, the light return might not be coming from the optimal high angle, as well.

In the specific recent case, I believe the table size (and corresponding crown height) was the main reason why the "poorer" cut stone looked better. The stone with 0.9HCA and a perfect IS had a 59% table, and the stone with 2.4HCA and a bit of leakage in the IS had a 56% table. A smaller table leads to more fire and scintillation, which is what I think happened there.

Thread here for reference:
[URL='https://www.pricescope.com/community/threads/finally-have-idealscopes-best-diamond.192117/']https://www.pricescope.com/community/threads/finally-have-idealscopes-best-diamond.192117/[/URL]

 

[msop04]

Short answer: Everyone's eyes are different, and no tool encompasses everyone's visual taste.

Long answer:
I suppose you're asking because of the other thread where an inferior HCA and IS led to a better-looking stone. No tool used here will tell you definitively whether one stone is better than another. The tools only narrow it down to safer bets.

The HCA tool doesn't have a single "ideal" measurement, but rather judges how the measurements work together to create a well-cut stone. Low-HCA stones generally perform better than High-HCA stones, but there are exceptions.

Idealscopes measure light return, but not the method of return. A stone with a great IS may suffer in fire and scintillation. If a stone has been dug around the girdle, the light return might not be coming from the optimal high angle, as well.

In the specific recent case, I believe the table size (and corresponding crown height) was the main reason why the "poorer" cut stone looked better. The stone with 0.9HCA and a perfect IS had a 59% table, and the stone with 2.4HCA and a bit of leakage in the IS had a 56% table. A smaller table leads to more fire and scintillation, which is what I think happened there.

Thread here for reference:
[URL='https://www.pricescope.com/community/threads/finally-have-idealscopes-best-diamond.192117/']https://www.pricescope.com/community/threads/finally-have-idealscopes-best-diamond.192117/[/URL]

Very well said, GoSounders.

 

[teobdl]

Yes, GoSounders, the other thread is what prompted my post. I didn't want to hijack the other thread and make it a discussion about using IdealScopes and HCA.

A diamond with a HCA <2 and a great idealscope performed worse than one with a fair amount of leakage. This is a big deal. PS purports to have relatively simple way of sifting through a thousands and thousands of diamonds to find top performers. In that person's case, if s/he had just presented the HCA and IdealScopes for the two diamonds, I don't think one person would have chosen the one with leakage and HCA > 2. A few may have said they didn't like the table size (which I did point out in that thread), and said pick a couple others, but the majority probably would have said, "HCA <2 and idealscope looks perfect--go for it."

It makes me question the system that we use a bit more. With my limited diamond experience, I'm happy to have just gotten a dummy-proof BGS. But others, like the poster in that thread, rely on "prosumer" advice to sort and select. I'm very happy for this community and the knowledge they bring to diamond naive consumers. I'm just pointing out that most prosumer advice would have judged wrongly, and I'm wondering if there are red flags for lesser-performing diamonds that otherwise pass HCA and IS.

 

[delight]

If you want to be smart, never make a round diamond purchase based on an Idealscope. Make your judgement based on ASETs. Good Idealscope images still hide issues that ASETs will show.

 

[chrono]

ASET has its own set of limitation too. I've read somewhere that IS is better for rounds?

 

[Christina...]

Brilliance can be affected by a number of things, for example clouds and twinning wisps can interfere with a stones brilliance yet have a beautiful corresponding idealscope image. Girdle enhancements can negatively impact a stones performance, surface graining and internal graining can also affect brilliance yet to my knowledge, none of these will show up in idealscope images.

It's also important to consider the positioning of the stone when the image was taken. If the stone is even slightly tilted it will appear as though there is slight leakage under the table even if none exists. Another important thing to consider is that these images are monoscopic and as humans we view them in stereovision, sometimes the minimal leakage shown on an idealscope is impossible for the human eye to detect. Also, I believe the point was already made, but, idealscope measure light return, not what type of light is being returned, so even two stones with very similar IS images, could perform very differently in a side by side comparison.

 

[Christina...]

While I really do think that all the new gemological stuff like ideal scopes and ASET images are super helpful, it's also feels like trying to decide if food is good by only looking at the menu and never taking a bite. Everyone has different taste, literally.

This is very true and why I think it's a good idea to ask the gemologist WHY he chose one stone over another, especially when it goes against what appears to be the logical choice. We can ask the waiter what he would recommend, but if he says 'the broccoli' well, then I'm ordering something else!

 

[teobdl]

ice_baby-- do you remember what the cut grade was for the diamond with whack symmetry?

Also, diamond store lights are meant to sell diamonds... even the dogs. I wonder if that same stone would have looked as good in as many different lighting situations as the precision cut diamond.

 

[Christina...]

ASET has its own set of limitation too. I've read somewhere that IS is better for rounds?

Is this the thread that you were thinking of Chrono?

[URL='https://www.pricescope.com/community/threads/do-not-request-aset-images-for-round-diamonds.153890/']https://www.pricescope.com/community/threads/do-not-request-aset-images-for-round-diamonds.153890/[/URL]