HCA

[abbymax825]

i have read that some people feel that a HCA score above 1.5 is superior in visual quality than a score below 1.5 because of loss of contrast. Or is it a score of below .5 that there is a loss of contrast. A diamond we are looking at has a score of 1 ex, ex, ex, vg. What do you think of its visual performance?

 

[pqcollectibles]

Actually, Abby,.... Some people prefer an HCA score between 0.5 and 1.5, so your score of 1 would be GREAT!!

 

[valeria101]

The HCA comes with the "reading instruction" that scores above 2 indicate excellent cuts (or potential optical performance, since the HCA itself does not cover all the factors critical for light return). This is not far from 1.5, and the difference is not of meaningful size.

The "2" line is already drawn with buying safety (and the HCA's integrity) in mind... isn't it Garry?

 

[pqcollectibles]

The general feeling among the pros that I've seen comment is,.... Below 0.5 and above 1.5 you tend to loose contrast. In between 0.5 and 1.5, you tend to get the overall better performers with the best balance and contrast.

 

[abbymax825]

with the same diamond, i put in the diamonds crown and pav %'s and it came out with ex,ex,ex,vg 1 and when i put in the same diamonds angles for crown and pav I got ex, ex, ex, vg 1.6 any reason for the difference.
1.46
I I1
depth 60.8
table 56.3
culet 0.6
crown angle 34.3
crown % 14.6
pav angle 41.0
pav % 43.2
7.34-7.37x4.44mm
i'm not really worried about the difference, i think that the diamond is a great performer, just wanted an explanatino as to why the difference

 

[kpebbles]

I believe inputting angles gives you a more accurate score than the percentages.

 

[Garry H (Cut Nut)]

It says this about 2mm from the thing you click called "go"

Select angles or depth % for Crown and Pavilion. Angles are more accurate.

and there is a link that tells you why