Should I be concerned about contrast in a diamond with HCA 0.7?

[Kim N]

I did a search on the PS search engine to find out more about the pros and cons of HCA scores above and below 1.0. I know it''s all personal preference, but I prefer to have good contrast in a diamond. I know nothing will compare to seeing the diamonds in person, but will there be less contrast in a diamond with 0.7 HCA score as opposed to one with 1.2 or 1.3 score?

 

[strmrdr]

depends on the angles.
For a ring a pavilion angle angle under 40.6 can be an issue.
Some 40.6 are fine and others are a problem depending on what is in the average.
Its a diamond by diamond decision.
What are the crown and pavilion angles?

Further its complicated by that with long lgf% it will have less effect than with short lgf% and can even be a good thing with some combos.
So it really is a case by case decision.

 

[Kim N]

Storm,

The crown is 34.9, and the pavilion is 40.6. Would those angles be a problem?

Also, I was looking at two other diamonds with HCA 0.9. One had crown 34.7, pav 40.7. The other had crown 35, pav 40.6. Should I be concerned about lack of contrast in those with HCA 0.9?

Thanks!

 

[strmrdr]

34.9, 40.6 == moderate possibility of a problem, but not always.
crown 34.7, pav 40.7 == should be fine
crown 35, pav 40.6 == case by case, but should be ok, 35.4 would be better.

 

[Kim N]

Thanks, Storm! I appreciate it.

 

[Kim N]

One additional question: Is the potential loss in contrast something I can see in the IdealScope image?

 

[strmrdr]

Date: 10/25/2005 4:35:59 PM
Author: Kim N
One additional question: Is the potential loss in contrast something I can see in the IdealScope image?

no

 

[JohnQuixote]

Date: 10/25/2005 4:35:59 PM
Author: Kim N
One additional question: Is the potential loss in contrast something I can see in the IdealScope image?

What you can see in the ideal-scope images is whether light performance is robust or not. Remember the crown and pavilion angles are (a) averages of 8 numbers each and (b) subject to a small degree of error, depending on whether it was Ogi, Sarin or Helium & how well the machine was calibrated. If it''s an AGS diamond you can compare the grading report numbers to a Sarin, if one was run.

Example: We have a number of AGS diamonds listed at 40.6/34.9. In some cases our local Sarin returns slightly different numbers than those on the report. Still, we always list them at the angles given on the official lab document, since those numbers are considered the authority. This is when the IS image is helpful to verify light performance in broad terms.

We visited this a bit back in this thread too, Kim

When well-cut with good patterning and effective minor configurations, diamonds at these angles are wonderful for rings, pendants or belly-buttons. If not well-cut, or with combinations of minors that don''t compliment the major angles, you need to evaluate the diamond to be sure there is not a loss of contrast or performance.

 

[JulieN]

belly buttons, eh?

 

[JohnQuixote]

 

[Kim N]

Thanks for the additional explanation, John. LOL about the belly buttons.

 

[Garry H (Cut Nut)]

I think you could all be navel gazing a bit.

I am seeing more and more diamonds with upper and lower girdle painting and digging than ever before.

You can easily be caught out - or your ranges extended.
As John says - look at the ideal-scope (or ASET) image and you can get a better idea.

 

[strmrdr]

Date: 10/25/2005 10:34:18 PM
Author: Garry H (Cut Nut)

As John says - look at the ideal-scope (or ASET) image and you can get a better idea.

neither of which show the problem.
It is one of those things that you have to trust your vendor with.


There is another issue here if one likes a lot of contrast and fire in a diamond they are better off looking at more midrange angles and short lgf% or better yet asschers :} which are the ultimate contrast diamond cut.

A mid 34.x crown, high 40.x pavilion , 75% lgf%, 50%-55% star, with great optical symetry, will be a better combo for lots of contrast and tons of fire than the ones under consideration.

 

[strmrdr]

say something like this one:

http://www.goodoldgold.com/1_017ct_i_si2_h%26a.htm

 

[strmrdr]

or its little brighter twin sister:
http://www.goodoldgold.com/1_012ct_i_si2_h%26a.htm