HCA vs. Idealscope

[targa]

if a diamond performs well on the HCA calculation is it possible still to have poor lperformance on the idealscope?

 

[strmrdr]

yes.
the hca uses the averages and whats in the averages can be important.

 

[targa]

then is the converse true as well, nice idealscope with high hca number? if so, then IS images become more important in stone selection- how come so many vendors including some on PS don''t use them?

 

[belle]

not all stones look so good under an idealscope

 

[Garry H (Cut Nut)]

IS wins over HCA

Vendors need to have the stones in house to photograph them

it is hard to find stones that look great under the ideal-scoppe

 

[valeria101]

Date: 1/3/2006 1:48:54 PM
Author: targa

then is the converse true as well, nice idealscope with high hca number?

There are some... not too many. E.g. where painted or dug facets help light return under table (found one or two with HCA over 3 recently, they might still be in the database here); oter cases may happen - never tried to make a list of such things.




if so, then IS images become more important in stone selection- how come so many vendors including some on PS don''t use them?

Typically, the stones ever presented with whatever details sound good about them - be it only lab reports (or not even) or a full bunch of bells and whistles

 

[valeria101]

The author of these images should know better if I am seeing things or what... Taking the meaning of the HCA scores and IS images as much as I understand them... these two seem to make a good example for your second question (about good IS and 'bad' HCA).

I don't know waht exactly was modified about the cut to improve light return under the table to that point - the wider variation of girdle thickness hints to some twist of the pavilion facets (azimuth modification, 'painiting' or 'digging' as it was reffered to earlier on this forum), but I would rather not venture to guess.

I am surely no expert - these looked interesting enough to mention. Hope you find them that way too