Converting percentages to angles

[GIJoeCam]

Quick simple question: Is there a simple way to approximate the Crown and Pavilion angles if the Crown and Pavilion measurements are given in percentages?

Thanks!

-Joe

 

[StonesThrow]

Date: 3/10/2006 1:45:50 PM
Author:GIJoeCam
Quick simple question: Is there a simple way to approximate the Crown and Pavilion angles if the Crown and Pavilion measurements are given in percentages?

Thanks!

-Joe

It seems I read a thread about this a while ago, but I can''t find it now. But as I understand it, the numbers you''d get would be exactly that: an approximation...which may or not be indicative of the cut quality of the stone in question. This approximation (rounding) is exactly the kind of thing that is degrading the effectiveness of the new GIA cut tool (see thread stickied at the top of RockyTalky).

As an example of the effect approximation can have...using the default parameters given when you load the HCA page here on Pricescope gives a 0.4 HCA score for this fictional diamond. Changing the pavilion angle by .1 (to 40.4) gives a 0.6 on the HCA, and changing it to 40 gives a 1.6 on the HCA. To some, that difference is definitely noticeable.

I''m by no means an expert...I wish I could find you the thread I''m thinking of, but I hope I made a little sense and am not totally off base.

 

[Dancing Fire]

Date: 3/10/2006 1:45:50 PM
Author:GIJoeCam
Quick simple question: Is there a simple way to approximate the Crown and Pavilion angles if the Crown and Pavilion measurements are given in percentages?

Thanks!

-Joe

yes.... a sarin or helium scan.

why make it tough on yourself?

 

[Mara]

No, because percentages are rounded. You could get an angle range but it wouldn''t be exact because there''s no way to know if it was rounded up or down.

This is why sometimes some stones score well on the HCA with % but with angles they don''t. The angles are most accurate.

Get a Sarin or similar and have them give you the angles.

 

[Maria D]

To approximate using basic trigonometry, convert percentages to decimals and plug info into the formulas shown in the file I uploaded (or at least I think I did!). For example, if table percent is 55%, convert to 0.55.