Some expert opinion on this... Leonid ??? Cut Nut ???

[Stephan]

As Aljdewey noticed in this tread, if you do a search by cut quality, there is a problem with the HCA results.
Look at the picture below and then run the same numbers with the cut adviser, the results will be different.

Why?

 

[pricescope]

Thanks, Stephan. Let me check it out...

 

[aljdewey]

Stephan, I actually answered this in the same thread.




I noticed this phenominon about 6 weeks ago when I bought my stone. I asked Garry why the results came out different.




His answer was: The search-by-cut quality results on pricescope allows the HCA to read specific information on the girdle, so it's more accurate.




In the method of manually entering the angles, etc. you are not asked to enter girdle information, so the HCA *assumes* a medium girdle.

 

[pricescope]

I ran the first three by Depth, Table, Crown and Pavilion. HCA results are the same.

Which stones in particular have different HCA results, Stephan?

 

[aljdewey]

Leonid......if you click on the thread link that Stephan provided, you'll see my two posts of different HCA results on the same stone.

 

[pricescope]

Oh, you are talking about different EX and VG grades... I found the reason of discrepancy (in the search page) and fixed it. Thanks!

The problem was only with fire and scint ranges. HCA scores should be the same nontheless.

 

[Mara]

Stephan, AL's response is right on...Garry noted this a few weeks ago in a thread about this same question. One is pulling specific data and the other is making an assumption. Using the PScope cut quality HCA scores will be more accurate at this point.




Garry--can you add in a girdle choice (e.g. girdle range OR just the average (e.g. medium)) into the next rev of the HCA so that people can view the most accurate results?

 

[aljdewey]

Leonid....I'm confused. How could you "fix" it given Garry's former explanation?




Garry said that the PS cut quality takes information on the girdle, which is MORE accurate than just using the cut advisor manually. Why would you want to change that?




And also, it affected more than just fire/scintillation....on my stone, it changed the spread from VG to EX.

 

[pricescope]

Hi Aljdewey,

I haven't read Garry's comments yet. I just noticed difference between ranges for fire and scintillation.

My fix shouldn't change anything for Cut Adviser page. I only fixed discrepancy for fire and scintillation ranges/grades as they shown in the search by cut quality.

 

[aljdewey]

Hmmm....that's interesting.




Since you made that "fix", the stone now scores 1.6 ex-ex-ex-ex.......even more disparate from the manual version of the HCA.




Curious.






1.256, H, SI2, 0 (H&A), 1.6-EX
ex-ex-ex-ex, 60.6, 56, 34.8°, 40.9°, AGS, 1.0-1.4, pt, id/www.pricescope.com/idealbb/images/smilies/3.gif[/img]>/www.pricescope.com/idealbb/images/smilies/3.gif[/img]>

 

[pricescope]

Aljdewey:

----------------
....that's interesting.
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OK… My quick fix made it worse.

I hope I found the real reason and it should be in sync with the next update on Monday.

The problem was with rounding data for Search by Cut Quality.

E.g. if fire scores 0.43 and rounds up to 0.4 it will be shown as EX in the search results while manual cut adviser will show it as VG.

 

[Stephan]

I think that with the total depth, table %, pavilion and crown angle, the cut adviser has enough data's to calculate the girdle...

 

[pricescope]

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On 1/24/2004 4:15:57 AM Stephan wrote:

I think that with the total depth, table %, pavilion and crown angle, the cut adviser has enough data's to calculate the girdle...

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It won't be very accurate though.

 

[aljdewey]

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On 1/24/2004 4:22:09 AM leonid wrote:

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On 1/24/2004 4:15:57 AM Stephan wrote:





I think that with the total depth, table %, pavilion and crown angle, the cut adviser has enough data's to calculate the girdle...

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It won't be very accurate though.

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EXACTLY right, Leonid.....and that's what Garry said. So no, Stephan, it's not intuitive enough to calculate the figure.

It doesn't *calculate* the girdle....it *assumes* a medium girdle and assigns values based on that assumption in concert with the depth/table/crown/pavil entered. Please go back and look at the results for the manual HCA scores. Every result plainly states "The result is for a symmetrical diamond with a medium girdle and very good polish".

My point, Stephan, wasn't to devalue the HCA....I think it's a very helpful tool. Rather, I was opining in the other thread that the wise diamond shopper shouldn't discard a diamond from personal consideration just because it scored VG instead of EX on parts of the HCA.