Cut Adviser?

[hoovillemd]

I have been keeping a close eye on how my diamond scores on the cut adviser.
I have just noticed that when I enter the angles(35.1/40. I get a score of 1.7 but when I enter the %(15.3/42. the score is 0.6. This is a big jump. Does anyone know what number is correct? I will give you all the figures and maybe someone will have a true value.

The Diamond is an AGS Ideal 0 H&A
Table: 56%
Depth: 61.2%
Crown: 15.3% or 35.1 angle
Pavillion: 42.8% or 40.8 angle
Culet: 0%

Does anyone know if the % or Angle is more accurate and why there is such a big difference?


Thanks Alot for everyones help
Matt Dabney

 

[hoovillemd]

Does anyone know who I might contact about this?
Thanks

 

[strmrdr]

It is my understanding that the angles are much more accurate.
There are people here that will be able to answer better than I can on how much more accurate.

 

[hoovillemd]

Thanks alot for your quick reply strmrdr. I will look forward to everyone elses info.

 

[aljdewey]

Hooville: Using the angles is more accurate. Using percentage means you are using figures that have rounded off. That's hugely less accurate than going with the *actual* angles.




Think of it this way.....there's a serious difference between $851.00 and $900. Under the percentage rounding system---because it's more than "eight and one-half hundreds"----$851 would be rounded up to $900.

 

[Garry H (Cut Nut)]

Excellent example of why angles are essential info over %'s.
Note that the table % is rounded and in actual fact the crown angle HCA has calculated would be 34.76.
Also the depth of the stone is shallower because the scan has not picked up the presence of a small culet.

IF YOU HAVE ANGLES ALWAYS USE THEM.

%'s reduce scores by about 0.3

 

[Garry H (Cut Nut)]

oops
forgot

 

[mike04456]

Garry, I've been wondering: is there a theoretical diamond out there that would score a 0.0 (or even less)? Or is the program structured so that the minimum score is going to be around 0.1? Or something higher?




Just curious.

 

[aljdewey]

LawGem, a few folks have commented recently (although I'd love to hear from Garry on this too) that super-low scores on this HCA aren't optimal, either.




The thought process is that stones below a 0.6 won't have enough contrast....kind of like reciting a speech in a complete monotone with no inflections.




Garry.....input on this?

 

[Garry H (Cut Nut)]

0.0 is impossible

I think.
if the spread = 0.0 then some other factors will not be 0.0

 

[Mara]

What about a 0.6 or a 0.4 Garry. How does such a low score affect the stone? I have heard it means there won't be as much contrast? Thoughts?




Secondly, this is why we stress ANGLES to people over %'s....the %'s can give you the nice low score and then angles bump it up a point and a half.




What if the %'s give the stone a 1.8. From my experience with typing in %'s then angles, that same 1.8 as % will be more like an almost 3.0 with angles. That may be a purchasing deal-breaker for someone...but if they don't have the angles, they won't know for sure.

 

[aljdewey]

Garry....since you're here....another question:




Why is it that when I do a search by cut quality, some stones will reflect different results (not in the score but in the ex/vg) then they do if I enter it manually?

 

[Garry H (Cut Nut)]

A can you give some eg's?

 

[Mara]

Garry....




What about a 0.6 or a 0.4. How does such a low score affect the stone? I have heard it means there won't be as much contrast?




/idealbb/images/smilies/confused.gif

 

[aljdewey]

Yup.....


This is from the PS cut-quality search....see all ex?




1.244, H, SI2, 0 (H&A)
0.9-EX
ex-ex-ex-ex, 60.5, 56, 34.6°, 40.7°, AGS, f 0.7%-1.4%, pt, id, id, neg, $5690*‡/www.pricescope.com/idealbb/images/smilies/3.gif[/img]>/www.pricescope.com/idealbb/images/smilies/3.gif[/img]>


Put the numbers in manually, though, and get VG on the spread instead. Why?




Selected: 60.5% depth, 56% table, 34.6° crown angle, 40.7° pavilion angle
The result is for a symmetrical diamond with a medium girdle and very good polish
Note: HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.

 

[Garry H (Cut Nut)]

OK - I see the problem.
There are 2 slightly differentmethods - the search by cut quality has access to better girdle data - which we do not trust people to get or enter online.
The actual spread index is on the cusp of VG / Ex.

Change either 0.7% to 0.8, or 1.4 to 1.5 and you get VG spread - it is that close.

Not a big issue - because it is so hard for people to get good quality girdle data - we work out the girdle by subtraction - so even table rounding etc introduces a small variable.

Make sense?

 

[Mara]

Garry doesn't want to answer my questions...I'll just go CRY in the corner....

 

[Garry H (Cut Nut)]

Sorry Mara - its Xmas here

a low spread means a shallower stone which can appear darker if you stick your head up real close.

But if you want a stone for a pendant or earrrings they are very big and no one can get that close to block the light with their noggin

Shallow stones have very little leakage, but slightly less light return because of head obstruction.

The areas that are dark can display more fire - even if the crown angle is low.

 

[aljdewey]

----------------
On 12/4/2003 7:17:52 PM Cut Nut wrote:





OK - I see the problem.
There are 2 slightly differentmethods - the search by cut quality has access to better girdle data - which we do not trust people to get or enter online.
The actual spread index is on the cusp of VG / Ex.

Change either 0.7% to 0.8, or 1.4 to 1.5 and you get VG spread - it is that close.

Not a big issue - because it is so hard for people to get good quality girdle data - we work out the girdle by subtraction - so even table rounding etc introduces a small variable.

Make sense?
----------------

Yup.....and considering that's my newly purchased stone, I'm DELIGHTED to hear that. Woo-hoo!

 

[valeria101]

----------------
On 12/4/2003 8:12:43 PM Cut Nut wrote:

[... Big] spread means a shallower stone which can appear darker if you stick your head up real close.----------------

So shallow stones look good only when not looked at

I'll write this down on my jewelry case

 

[aljdewey]

----------------
On 12/4/2003 11:55:02 PM valeria101 wrote:

So shallow stones look good only when not looked at

I'll write this down on my jewelry case
----------------

While you're writing that, you may want to also write this: Semantics, I know, but important points:

1. Garry didn't say shallow stones didn't look good, he said under *some* conditions they can look *dark*. There was no implication that shallow stones are undesirable or *bad*.......dark is not specifically synonymous with bad.

2. He said they can look dark if your head obstructs the light.

3. And yes......if the only way you can "look" at your stones is with your head glued to them (instead of normal viewing distance like earrings, etc.)....then yes, expect them to look dark.