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Which one sparkles more? Do I trust my eye or HCA?

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Date: 7/1/2009 9:06:41 PM
Author: Garry H (Cut Nut)
When you looked at the stones it is helpful to hold them so minimal light can enter the pavilion - if they are in tweezers this masks the leakage effect.
My experiance is that the E will show dull zones when it is dirty.

But in this case it is being helped by painting - which is an effect that you can read about by searching for Eight star 8* and ACA new line - so the HCA score is probably effectively closer to around 3.
Click to expand...
There you go Triple, an experts advice and from the creator of the HCA to boot!
 
The point of the HCA can be to help train your eyes so that you know you can trust them. Without some training, the eyes are not the best disciminator. It takes a little effort to learn what to look for and what to see.
 
HI everyone,
Triplec- There are many here who believe "leakage" to be a problem in diamond number three.
However, there are also many experts who don't post here ( and one that does) who feel that such leakage is insignificant in real life- many who would feel there's no problem at all with diamond number three based on:
1) the GIA report
2) Your reaction to it.

I've shown this before by posting photos of a stone that did better on the ASET/IS, that was not as pretty to me as one that had a lesser ASET/IS image.
For someone who wants to use the HCA, or ASET/IS, they are valuable tools.
But they don't work for everyone- and you may very well be in the group for who the results of the HCA and IS ASET are irrelevant. There are many other ways of selecting an exceptionally well cut diamond.
Trust your eyes.
 
The leakage issue is a can of worms unto itself. The thinking at Imagem is it isn''t so much leakage as dark places where light is guided away from as it travels, refracts and reflects internally in the stone. Light is refracted to other places in the stone which concentrate and return the light leaving some dark places which we often refer to as places where there is leakage. Some light does go out on the pavilion of a diamond, but for the most part it is not lost to our eyes, but becomes concentrated in brighter, and less bright zones. This sets us up to see the sparkle, symmetry and contrast which we find attractive about faceted gems.
 
I don''t believe the IS images will tell you anything about sparkle. For that you will have to rely on your eyes.
 
David- here on PS leakage is an issue.
IN the diamond trade as a whole, not so.

It''s truly remarkable the amount of research done into why a diamond looks as it does- and many Pricescope experts are clearly at the forefront in this regard. But the bottom line for many is that how it looks is more important that why it looks that way.

From what Triplec seems to be saying, she fits into the group that''s more interested in how the diamond looks. IMHO a discussion critical of the diamond she''s picked based on it''s visual characteristics is needlessly alarming to the consumer.
 
50% of subjective Leakage is just 15% lost in LR

See Map
it is reason why we disabled The calculation of Leakage mono and Leakage Stereo in Cut Quality estimation in DC since April 20, 2004
For diamond Light Performance is important only Strong Big Leakage Zones
Third diamond has not strong Big Leakage Zones
we changed Leakage to Black Zones

Leakage-LR.gif
 
Leakge is pretty much "a non-issue in the diamond trade", I agree. HOWEVER, it is a non-issue because dealers have buried their heads in their diamond parcels and just have no handle whatsoever wiith technology. "Leakage" is a widely a mis-used word among us techno guys on Pricescope. Most say leakage is where there is no light coming back to the eye. My informed partners tell me that there is really very little light escaping at these dark zones, but it is light that is being bent and reconcentrated and returned elsewhere in the diamond which makes some areas dark in appearance compared to others which are bright in appearance. Leakage is just a poor choice of words. There are dark and bright zones in faceted gems which contribute to their contrast and sparkling effect. We need dark zones as well as bright zones to get a beautiful appearance.
The HCA is a good tool for training our eyes and for screening stones. In the end, the eyes are the way to go, but only after a period of training them so that the eyes are skilled at their task.
 
Serg, can you show an IS image of what you term strong leakage? How strong is strong is what I want to know.
 
Date: 7/2/2009 3:16:04 PM
Author: Stone-cold11
Serg, can you show an IS image of what you term strong leakage? How strong is strong is what I want to know.
Click to expand...

Stone,
See image for Pavilion 41,4 Cr34.5
Leakage is at least 67%+13%+1%=71%
+ direct reflection to observer direction is 17%. Totally LR loss is 89%
It will Dark zone for any Cyclops or Photocamera. For Human stereo View Leakage even for this diamond is much more less. If you tilt diamond just on 5 degree most white zones become red. Angle distance between left and right observer direction fro normal distance is near 7*2=14 degrees

For Pavilion 41,2 Leakage is much more less even for Cyclops

Important comments. Even for Human stereo Vision P40.7C34.5 has bigger LR than P41.4C34,5.( But difference is not so dramatic how you could see in IS or ASET)

StrongCyclopicLeakageP41_4C34_50.jpg
 
Date: 7/2/2009 3:14:53 PM
Author: oldminer
Leakge is pretty much 'a non-issue in the diamond trade', I agree. HOWEVER, it is a non-issue because dealers have buried their heads in their diamond parcels and just have no handle whatsoever wiith technology. 'Leakage' is a widely a mis-used word among us techno guys on Pricescope. Most say leakage is where there is no light coming back to the eye. My informed partners tell me that there is really very little light escaping at these dark zones, but it is light that is being bent and reconcentrated and returned elsewhere in the diamond which makes some areas dark in appearance compared to others which are bright in appearance. Leakage is just a poor choice of words. There are dark and bright zones in faceted gems which contribute to their contrast and sparkling effect. We need dark zones as well as bright zones to get a beautiful appearance.
The HCA is a good tool for training our eyes and for screening stones. In the end, the eyes are the way to go, but only after a period of training them so that the eyes are skilled at their task.
Click to expand...
Dave- I would respectfully disagree. The only valid method of training people how to identify well cut diamonds involves using actual diamonds. Even if one wanted to use the IS/ASET and HCA, any real, meaningful training will require the diamonds to be physically examined in relation to the ASET/IS/HCA.

In terms of leakage: We agree that there are many sellers who don;t understand diamonds, nor care what they sell. But there are MANY diamond dealers that do understand diamonds, and care a great deal what they sell. It's not fair to lump all dealers together as people with their heads buried in the sand ( or their parcel papers) The technology used to cut diamonds, is completely different than the technology used to select diamonds.
A diamond cutter not using today's latest diamond technology today is....well, out of touch and probably out of business. However the tools for assessing the quality of cut are not in the same category. It IS possible to select the finest cut diamonds without IS/ASET and HCA.
AS you have said- "leakage" is a just a poor choice of words, and it's frequently misused.
 
Serg, how much more significant must the leakage be or the area large enough before it is significant enough for you to consider as strong big leakage zone?

Thanks.
 
Useful explanation and graphics Serg.



Date: 7/2/2009 4:33:45 PM
Author: Stone-cold11
Serg, how much more significant must the leakage be or the area large enough before it is significant enough for you to consider as strong big leakage zone?

Thanks.
Click to expand...
In my experience a lot of it depends on lighting/environment. I've seen worse examples which are fine under spotlights (much looks fine under spots).

It also depends on the diamond. For instance, the wireframe example at 41.4 above assumes all 8 mains are precisely 41.4. Actual diamonds may have a number of p-mains several tenths away from the listed avg and/or variations in optical symmetry which may influence degree of visibility.
 
Date: 7/2/2009 4:51:47 PM
Author: John Pollard
Useful explanation and graphics Serg.




Date: 7/2/2009 4:33:45 PM
Author: Stone-cold11
Serg, how much more significant must the leakage be or the area large enough before it is significant enough for you to consider as strong big leakage zone?

Thanks.
Click to expand...
In my experience a lot of it depends on lighting/environment. I''ve seen worse examples which are fine under spotlights (much looks fine under spots).

It also depends on the diamond. For instance, the wireframe example at 41.4 above assumes all 8 mains are precisely 41.4. Actual diamonds may have a number of p-mains several tenths away from the listed avg and/or variations in optical symmetry which may influence degree of visibility.
Click to expand...
Thats the thing isn''t it, too many variables to give a definite answer?
 
Date: 7/2/2009 4:33:45 PM
Author: Stone-cold11
Serg, how much more significant must the leakage be or the area large enough before it is significant enough for you to consider as strong big leakage zone?


Thanks.
Click to expand...

25%-50% from Total Power ( what is roughly 50%-71% from maximum Intensity In IS/ASET images) is Medium leakage. Biggerleakage is strong Leakage.

Size is much more complex issue( It account eye angle resolution what depends from brightness and contrast, so also very important clastarisation ( if you see separate facets under table for P41.5 for you it seems as one ring. ALso important is it static or temporal Leakage zone. Brain account the Time during area is visible . So small static zone is much more critical than bigger Temporal zone( which can even create positive contrast) . But Very bug Temporal zone is bad too)
Could I ask you Who are you?
 
Serg, just a consumer. Engineer by training.
 
Date: 7/2/2009 4:51:47 PM
Author: John Pollard
Useful explanation and graphics Serg.




Date: 7/2/2009 4:33:45 PM

Author: Stone-cold11

Serg, how much more significant must the leakage be or the area large enough before it is significant enough for you to consider as strong big leakage zone?


Thanks.
Click to expand...

In my experience a lot of it depends on lighting/environment. I''ve seen worse examples which are fine under spotlights (much looks fine under spots).


It also depends on the diamond. For instance, the wireframe example at 41.4 above assumes all 8 mains are precisely 41.4. Actual diamonds may have a number of p-mains several tenths away from the listed avg and/or variations in optical symmetry which may influence degree of visibility.
Click to expand...

Thank you John,
you can find more in our
IDCC1 article
 
Date: 7/2/2009 2:08:33 PM
Author: oldminer
The leakage issue is a can of worms unto itself. The thinking at Imagem is it isn''t so much leakage as dark places where light is guided away from as it travels, refracts and reflects internally in the stone. Light is refracted to other places in the stone which concentrate and return the light leaving some dark places which we often refer to as places where there is leakage. Some light does go out on the pavilion of a diamond, but for the most part it is not lost to our eyes, but becomes concentrated in brighter, and less bright zones. This sets us up to see the sparkle, symmetry and contrast which we find attractive about faceted gems.
Click to expand...
that would be what I would call dark zones...
leakage is leakage, image 6 you can see the fingers through the diamond.
That is one of my first checks on a mounted diamond, can I see the setting through the stone.
What saves leaky stones is you tilt them slightly and those areas will often start returning light.

image007.jpg
 
Here you go at 2 degrees tilt, leakage is much less, this is also why a 2 eyed view can help cover leakage depending on how the diamond is viewed.
I have used exactly this test on diamonds in a b&m.
For years I kept a bright red business card in my wallet for doing this test when I didn't have my IS/ASET with or the jeweler wouldn't let me use them.
I call this soft leakage

leakageCompare.jpg
 
This one has what I would call hard leakage, it does not get less leaky with a slight tilt to the extent the above combo does.

evendeaperP2degrees.jpg
 
When I am designing diamonds and want to use leakage for contrast I will use soft leakage but not hard leakage.
Hard contrast kills to much performance.
Done right soft leakage can produce a lot of contrast scintillation.
 
as you can tell this is a complicated subject where there is disagreement among even those that have studied diamonds.
 
So hard leakage presumably is the result of much higher pavilion angle than this 41.4 degree? Around what score of HCA do you think that set in? Greater than 4?
 
Ok, thanks.
 
Date: 7/2/2009 6:27:27 PM
Author: Stone-cold11
Ok, thanks.
Click to expand...
complicated isn''t it.....
 
Ya, GIA rounding of numbers for the lower facet is definitely not going to be useful in these cases.

I am guessing the larger LGF number will be better for these cases?
 
Date: 7/2/2009 6:40:19 PM
Author: Stone-cold11
Ya, GIA rounding of numbers for the lower facet is definitely not going to be useful in these cases.


I am guessing the larger LGF number will be better for these cases?
Click to expand...
yep
 
Date: 7/1/2009 7:22:18 PM
Author: sarap333
I agree with stone-cold about the leakage in the IS for the E. However, maybe in real life the leakage is not apparent. Make sure to compare the stones under a table, away from direct light to see if the E goes ''dark.'' The other thing I''m wondering -- and others who know more about this than I do, please chime in -- is that maybe what appeals to you about the E is that you like the combination of the long lower girdles (80%) and the E color. I had a stone with similar specs (a D with 81% lower girdle facets) and it was indeed white and sparkly. That may be the visual quality of the stone that is appealing to you, and there''s nothing wrong with that - colorless stones with long lower girdles have a definite zip to them, IMHO. I''d say double-check one more time in a dimly light part of the store to compare the two stones, and if the E still looks good to you, go with that one.
Click to expand...

Then SaraPJ''s observation makes perfect sense.
 
HI everyone!
I don't know if TripleC is even still looking on...
The conversation certainly has taken a life of it's own...

If she has been following and still wants guidance, is it safe to say that in this case, she should trust her eyes?
We can't really "recommend" any diamond we haven't personally seen- but based on the ASET/IS and TripleC's real life impressions, wouldn't it be safe to say she should go with her eyes in this case?
 
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