Experiment: Correlating HCA with Idealscope Images

[boredstiff]

I thought I''d try something out. I''m going to pick diamonds with varying HCA scores to see if the differences in scores translate to differences in idealscope images. Let''s see how this turns out:

HCA 1.4

 

[boredstiff]

HCA 1.8 (showing some slight leaking under table?)

 

[boredstiff]

HCA 0.8 (out of order)

 

[boredstiff]

HCA 2.2 (showing quite a bit of leakage -- does this count as a fish eye?)

 

[boredstiff]

HCA 2.6 (even more leakage)

 

[boredstiff]

HCA 3.8

 

[boredstiff]

HCA 1.3 (this is the one I am thinking of getting) See other post

 

[boredstiff]

Do the HCA scores generally agree with the quality of the IS images? What about for the 0.8, 1.3, and 1.4 stones?

Although I hear the advice to use HCA to weed out bad stones, the scores seem to me to correlate pretty darn well to the quality of the IS, even for low HCA scores. What gives?

 

[Lorelei]

Date: 8/26/2009 1:59:42 AM
Author: boredstiff
Do the HCA scores generally agree with the quality of the IS images? What about for the 0.8, 1.3, and 1.4 stones?

Although I hear the advice to use HCA to weed out bad stones, the scores seem to me to correlate pretty darn well to the quality of the IS, even for low HCA scores. What gives?

Interesting experiment, thanks for doing that!

The HCA is used for rejection not selection as you know, as it can't physically see the diamond it assumes top symmetry, can't allow for variations in proportion averages etc so it can't tell the whole story, nor did the creator intend it to be used for such. Basically the aim is to score below 2 to see if a particular diamond is worth pursuing then evaluate from there with IS, used in this way it is extremely useful. With image #4 it doesn't look like a fish eye to me, plus the HCA will generally warn if this is a possibility, as to any leakage it could be a result of the lighting but if it is leakage it is very slight and might not be noticeable in real life. The images of #5 and 6 show definite leakage which could be visible in reality, the image of the diamond you are interested in looks great.

 

[stone-cold11]

It should correlate well because IS is one of the method used in the construction of the HCA database.

But HCA is only taking in 4 parameters instead of the entired 3D model of the stone, such as star, lower girdle facets, optical symm and brillianteering of the stone, all of which can further impact the performance of the stone. So it is a cut off not a selection tool.

 

[Regular Guy]

Great user name.

Stone cold has among the most helpful points...

Date: 8/26/2009 3:54:13 AM
Author: Stone-cold11
It should correlate well because IS is one of the method used in the construction of the HCA database.

But HCA is only taking in 4 parameters instead of the entired 3D model of the stone, such as star, lower girdle facets, optical symm and brillianteering of the stone, all of which can further impact the performance of the stone. So it is a cut off not a selection tool.

and I think your experiment showed what it''s designed to do ideally, in consideration that 0 - 2 should be weighted equally, more or less.

I personally was surprised by a pick Stone Cold recently made for someone looking exclusively from JA stock. There were maybe 20 options to go through, and without having documented it, I''m guessing he looked at the IS for most of these to come upon one to suggest. But...I think all of these were AGS0 options. I would have thought (and am still unsure what to think) that IS results really, effectively, might be ignored once the 0 for AGS is given. But...the IS results were, it seemed, really pretty various for these, and this surprised me.

 

[stone-cold11]

RG, which thread is that from?

As mentioned in a previous thread, IS is monocular, makes leakage more obvious than our binocular vision. But if there is a choice, I would prefer one with less leakage in the IS.

 

[Regular Guy]

Date: 8/26/2009 10:32:07 AM
Author: Stone-cold11
RG, which thread is that from?

As mentioned in a previous thread, IS is monocular, makes leakage more obvious than our binocular vision. But if there is a choice, I would prefer one with less leakage in the IS.

This one.

JA is frustrating for me. The choice you found is not provided by JA in the search by cut db...where I would otherwise not care if it gets an AGS0...but...searching in the JA database alone for all options that fit the writers constraints did provide really many options...many of which WERE AGS0. I was puzzled why you selected the one you did, until I started opening them up, one by one, and saw that for the many AGS0 options, which did come with idealscope images...many didn''t look so hot...leading me to conclude you looked through these too, and chose the one you did, based on a similar analysis.

Was I right?

 

[stone-cold11]

Ya, looked at the IS of the H&A selection but don''t like any of them.

 

[Regular Guy]

But...they''re all AGS0, right?

Doesn''t anyone think that''s strange?

 

[Regular Guy]

Bored, btw, I think there''s a related thread, found in the "Helpful Threads Archive," up top...