What procedures to follow when reflectors cannot (any longer) help?

[strmrdr]

Date: 7/31/2009 2:42:45 PM
Author: litebrite

Storm, so the contrast patterns in asschers - this means that amongst the different patterns, that some are bound to reflect more light than others? I have always found the pattern in LaurenthePartier''s asscher to be most pleasing and I think I like the wide step pattern best b/c there''s a minimum of black contrast. Does the bright drop suffer from the 5 tilt angle problem? What about a really well cut bright drop?

A well cut bright drop the dark areas will flash at 1-3 degrees tilt.

"Also, thanks for the thoughts on hard vs soft contrast. Is that similar to dark black arrows on an H & A versus more silvery arrows?"
Dark close then silvery at a distance is what I was discussing above.
One with contrast issues the arrow shafts stay dark to far away.

 

[Serg]

Date: 7/31/2009 10:13:30 AM
Author: jet2ks
I don''t know about anyone else, but I am loving the technical aspects of this discussion. Some of it is still a little over my head (esp. some of the acronyms), but it is all interesting.

Date: 7/30/2009 9:15:13 AM

Author: Garry H (Cut Nut)


Sergey also mentioned that we have 2 eyes (stereo vision) the leakage from one view can be light return from another - this is imporant.

I know this was brought up by Serg in the other thread and is now a couple of pages old here, but I had a question about how this affects diamond viewing. Hope it doesn''t sound too stupid.


Garry, Storm and Serg, you have all mentioned hard contrast, static black zones, whatever you want to call them. How does the stereo optic view change that and how do you factor in viewing distance when looking for these? As the viewing distance increases the variation of angles between the two eyes decreases. So as the diamond moves further away, one of these zones should be both easier to detect due to the angle becoming more acute, and harder due to the eyes having to focus on a relatively smaller spot. Do you have an optimal distance for checking for these leakage areas?

Hi Jet,

we need account at least two facts to correct account Human stereo vision
1) Distance from left pupil to left ear is in more than two times less than from same pupil to right ear. For example for Yurii head first distance is 40 mm, second distance is 95 mm. It gives for distance 250mm( between nose and diamond) 9.1 degree and 20,8 degree. Sum is roughly 30 degree as in ASET, but ASET does not account what head obscuration is not symmetrical ( in perpindicular direction obscuration is bigger but less important for RBC).
2) distance between pupils is 55mm, what give 12,4 degree for 250mm and 7 degree for 450mm observer distances

if we account these two facts together we receive for some cuts and VFs effective obscuration angle is near 6 degree( for 250 mm) instead 15 degree in ASET.
for other cuts or VF''s it could be 9-11 degree.
In next 1-2weeks I will publish images for easy understanding, but I hope main idea is clear now.

 

[strmrdr]

Serg does raise an interesting point both IS and ASET overstate obstruction compared to on the hand view at 1/2 arms length or further.
That is why the arrows on rounds are more silvery than black unless there is a contrast issue.
The main fact is that no one scope or no one image can tell you everything about a diamond.
But there comes a point that you have to jump or you will be splitting frog hair for a decade.
I talk of them being pieces of the puzzle, when you get enough pieces to be comfortable, jump.

 

[jet2ks]

Thanks Storm,

Interesting looking at how the angle combination affects the contrast

Serg,

I''ll look for the article with images. I hadn''t done the math on it to come up with the exact angle variations. (I''m not even sure I could remember how at this point, back in college it would have been a snap). Is there any way to overlay images with the angles accounted for to get a better idea of what the brain processes from the two eyes? Maybe that will be in your article, I''ll wait and see.

The reason for the question was because I have been asking myself for a while now how well images on websites from a single lens camera or IS/ASET scope accurately reflect how a person views a diamond. This thread is greatly helping with my understanding.

Anyways, thank you both for taking the time to explain to a newbie consumer. Math and physics is just fascinating to me, even though I am far out of practice figuring the numbers any more. Combining those with something else (in this case, overheated carbon) to create beauty just takes it to another level.

 

[jet2ks]

Date: 7/31/2009 3:40:46 PM
Author: strmrdr
Serg does raise an interesting point both IS and ASET overstate obstruction compared to on the hand view at 1/2 arms length or further.
That is why the arrows on rounds are more silvery than black unless there is a contrast issue.
The main fact is that no one scope or no one image can tell you everything about a diamond.
But there comes a point that you have to jump or you will be splitting frog hair for a decade.
I talk of them being pieces of the puzzle, when you get enough pieces to be comfortable, jump.

Yes! I think that is what some people aren't understanding. The only way to really know what a particular diamond is going to look like is to see it in person--everything else just helps fill out the picture in your mind. I haven't seen anyone disagree with that, yet. When PS members ask for IS or ASET, we are getting more pieces in place, to the point where we are comfortable offering a recommendation--that point can be different for each person, shape or angle combination.

 

[Serg]

Date: 7/30/2009 4:41:24 PM
Author: Garry H (Cut Nut)

Date: 7/30/2009 1:43:58 PM

Author: Serg

Date: 7/30/2009 1:13:59 PM

Author: strmrdr

Date: 7/30/2009 9:15:13 AM

Author: Garry H (Cut Nut)


And another feature that is hard to describe - but i will try in the next few days - is that sometimes a stone can have an entire dark zoe thru a range of movements because of obstruction.

This is what I would term hard contrast.

Jon has a video of an asscher that shows it very well.

I don''t have a link at the moment.

Garry, good example for small such phenomena is some AGS0 princesses with 4 or more shevrons

Angles between shevrons are 1-2 degree and very often you can receive angles between opposite facets in range 44-46 degree. It creates 4 static black squares.

Sergey could you please do an image (send me an email if you are still away) or give us a better description?

see example

 

[Serg]

dmc file for upper image

 

[Serg]

Date: 7/30/2009 1:23:50 PM
Author: oldminer
It is truly amazing how over the top and complex this subject can become. What I see emerging is some sort of strategy which would well apply to the creation of finely cut and high performing diamonds, but something way too complex for ''grading'' diamonds. Grading is normally done under a rather simple lighting scenario, with an eye toward repeatabily, accuracy and consistency within this limited scenario only. The rest, the subjective and important judgment of personal beauty is done in as many environments as you have time to study the diamond in. Beauty appreciation is a separate thing from ''grading''.


So long as the understanding of these two elements, both highly important to diamond dealers and to consumers, are kept in separate arenas, this topic is not going off course. If anyone thinks that ''grades'' will arise from such complexity, I have serious doubts about it ever happening. We will have far better looking and more interesting diamond cuts based on these new techniques which are something to look forward to.

Surely, some elementsw of this high tech stuff will find their way to the grading labs in due course, but it will be a selective few bits, not the entire mass of this growing knowledge base.


I am more oriented around ''grading'', but there are many here who have design and beauty as their higher goals. Great thread!

Hi David,

please check


"c) Cluster approach to BLR data

The Master Stones Set will be divided into different BLR groups based on expert human grades; e.g. brilliance, scintillation, fire, and contrast. The same process will be performed by the computer based 3D model cut grades.

As a result we receive two sets of data that can then be compared: (1) Computation-based clusters and (2) Expertise-based clusters (fig. 3).
A proposed method for correlation between these two cluster maps is via ''Neural Networks'', a special statistical method for comparing data arrays to build a common system.

The BLR-based grades and the experts'' grades may match or not match:

If they do match, then the system is complete.
Clusters in the BLR grading match more than one cluster in the expert human observations; the match is not adequate.
Clusters have inadequate matching.
To complete the cut grading system, we may need to improve either the computed BLR set, or question the expert observers.
In this way the Master Stone Set may be used to verify various cut grading systems and 3D models and the ETAS approach may be used for both Cut Grading and devising new cuts.

This approach is robust against errors in both diamond expertise and BLR computation."
http://www.gemology.ru/cut/english/conferens-article/2.htm

 

[Serg]

Date: 7/31/2009 3:45:36 PM
Author: jet2ks
Thanks Storm,


Interesting looking at how the angle combination affects the contrast


Serg,


I''ll look for the article with images. I hadn''t done the math on it to come up with the exact angle variations. (I''m not even sure I could remember how at this point, back in college it would have been a snap). Is there any way to overlay images with the angles accounted for to get a better idea of what the brain processes from the two eyes? Maybe that will be in your article, I''ll wait and see.


The reason for the question was because I have been asking myself for a while now how well images on websites from a single lens camera or IS/ASET scope accurately reflect how a person views a diamond. This thread is greatly helping with my understanding.


Anyways, thank you both for taking the time to explain to a newbie consumer. Math and physics is just fascinating to me, even though I am far out of practice figuring the numbers any more. Combining those with something else (in this case, overheated carbon) to create beauty just takes it to another level.

re:Is there any way to overlay images with the angles accounted for to get a better idea of what the brain processes from the two eyes?

See
illustration. My my understanding Brain tries receive image with highest contract from both eyes



more you can find
http://www.gemology.ru/cut/english/conferens-article/6.htm

 

[strmrdr]

Serg can you explain this one please?
E) ray tracing study. Check cross ray ability

I think I know what your referring to but not sure.

 

[Garry H (Cut Nut)]

Date: 7/31/2009 5:51:17 PM
Author: strmrdr
Serg can you explain this one please?
E) ray tracing study. Check cross ray ability

I think I know what your referring to but not sure.

Storm Sergey is referring to what i posted on page 3 here: 7/30/2009 6:49:54 PM

And also mentiuoned in the blue part of the reply to Jet at the top of this page (4) P: 7/31/2009 3:29:09 PM


Hi Jet,

we need account at least two facts to correct account Human stereo vision
1) Distance from left pupil to left ear is in more than two times less than from same pupil to right ear. For example for Yurii head first distance is 40 mm, second distance is 95 mm. It gives for distance 250mm( between nose and diamond) 9.1 degree and 20,8 degree. Sum is roughly 30 degree as in ASET, but ASET does not account what head obscuration is not symmetrical ( in perpindicular direction obscuration is bigger but less important for RBC).

2) distance between pupils is 55mm, what give 12,4 degree for 250mm and 7 degree for 450mm observer distances

if we account these two facts together we receive for some cuts and VFs (virtual facets) effective obscuration angle is near 6 degree( for 250 mm) instead 15 degree in ASET.
for other cuts or VF's it could be 9-11 degree.
In next 1-2weeks I will publish images for easy understanding, but I hope main idea is clear now.
Sergey Sivovolenko
CEO OctoNus

For others trying to follow this - here is Bruce Hardings article that was written many years ago.
RockDiamond if you want to understand some background it would be worth your time to read it
http://www.gemology.ru/cut/english/faceting/f1.htm#viewer Bruce aka Beryl occasionally visits here and has been mentioned on the bias thread recently.

 

[Rhino]

Date: 7/30/2009 1:38:24 PM
Author: Regular Guy

Date: 7/30/2009 1:23:50 PM

Author: oldminer

It is truly amazing how over the top and complex this subject can become. What I see emerging is some sort of strategy which would well apply to the creation of finely cut and high performing diamonds, but something way too complex for ''grading'' diamonds. Grading is normally done under a rather simple lighting scenario, with an eye toward repeatabily, accuracy and consistency within this limited scenario only.

I don''t know Dave, and forgive me if my understanding is off, but I''ll take a stab at repeating what I''ve read.


There''s a difference between defining grading as how it is normally done, and historically done. I think AGS is a big enough player, to call their contemporary practice authoritative. I think they do capture an aset view, and then do many (90?) rotations. Is this the same, different, or consistent with doing a movie? I think it''s consistent with it. And is a strategy for appreciating a different result of light performance from different positions. This is current practice, based on, as I understand it, the need to grade, based on evaluating the diamond in different positions, rather than a static one, at least...

Yep. I think you''ve touched on a key point here Ira. At least with regards to the evolution of cut evaluation here on the net amongst us geeks. The static view, in a controlled environment can tell us as gemologist''s much about diamond quality, precision of cut, the ability of the pavilion to reflect what is entering it and the ability of the crown to draw in light from the brightest resources in environment.

The factor which dynamic optical testing takes into account (which we are exploring here) is the the asymmetrical, non static view in environments that are NOT predictable. Garry''s illustrations with of the pears and squares being one example. Live examples I can think of off the cuff are Asscher''s wherein there was too much blue in an ASET which would sometimes result in overdarkness and then in some instances not at all. Blue in an ASET doesn''t always translate to obstruction. In fact in spot lighting it can result in very strong fire. Bottom line ... different lighting will produce different results. The key is understanding how technology correlates to human observation. When you got that down ... its gravy. Unfortunately it''s not always easy. I''ve got it mastered on some shapes but certainly not all. That takes time and lots of observation testing.

Peace,

 

[strmrdr]

Thanks Garry is what I thought.
Basically optimize for in and out return outside the obstruction zone.

 

[Rhino]

Date: 7/31/2009 11:58:11 AM
Author: Rockdiamond
I think everytone agrees ''Trust me'' coming from a seller about a diamond you might like or not sounds pretty slimy.

But in fact, trust is exactly what has to develop for a person to buy.

Both stores, and websites have had to find ways of earning trust- and communicating what they find beautiful and why.

Personally I have found that photos, video and personal observations work incredibly well.... and that ASET would arbitrarily ''downgrade'' stones I have picked based on visual attributes- which is why we don''t use it.



However, even an ASET/IS needs to be interpreted using....well, our eyes, right?

Plus, consumers who have not taken the time to learn , or simply have no interest in learning the fine points of an ASET still need to trust the vendor interpreting it for them.



Again, I''m not trying to make this into a knock against reflector technology- and Ira, it''s your thread- but I really would like to know what some of the others think of the points I''ve raised here

Wazzup mang?

Not taking it as a knock whatsoever. The thing is this ... put yourself in the shoes of the consumer... wait ... put the consumer on hold a sec ... Let me speak from a vendor perspective. I call up cutting facilities, suppliers, manufacturers all the time for diamonds to have them sent in to inspect, You know as well as I do what the response is going to be 99.9% of the time when we ask them "How does this diamond look?" BEAUTIFUL is the general response. What''s even funnier is I''ve shopped competition WHOM I KNOW haven''t even seen the diamond and they say the same thing. Forgive me Dave but I''m a natural born skeptic. When a supplier says "It''s BEAUTIFUL" ... I want objective proof. ASET, IdealScope, DiamXray are some means by which to demonstrate that to a pretty strong degree. As I have mentioned earlier they are CERTAINLY not end/all be/all solutions ... they have their flaws and their drawbacks but when I say a diamond is beautiful, it gives credibility when you can point to hard evidence backed by testing of other laboratories and other experts in the field. Now ... if you or I are going to advise a consumer that a diamond is gorgeous or bogus when in fact reflector technology states otherwise ... the burden of proof lies on us to be able to demonstrate *why*.

My .02c

 

[Rhino]

Date: 7/31/2009 12:56:51 PM
Author: strmrdr
34/41 at 400mm for comparison

Personally ... I enjoy how the mains light up with this combo and focal length though I''m not 100% sure how far 400mm is from my face.

 

[Rhino]

Date: 7/31/2009 3:40:46 PM
Author: strmrdr
Serg does raise an interesting point both IS and ASET overstate obstruction compared to on the hand view at 1/2 arms length or further.

That is why the arrows on rounds are more silvery than black unless there is a contrast issue.

The main fact is that no one scope or no one image can tell you everything about a diamond.

But there comes a point that you have to jump or you will be splitting frog hair for a decade.

I talk of them being pieces of the puzzle, when you get enough pieces to be comfortable, jump.

Ever eat frogs legs?

 

[Serg]

Date: 7/31/2009 5:51:17 PM
Author: strmrdr
Serg can you explain this one please?

E) ray tracing study. Check cross ray ability


I think I know what your referring to but not sure.

Karl,

See below 4 images what demonstrate ability cross type( ray from eye to diamond has intersection with ray from diamond) rays to reduce obscuration

without tilt both rays( LeftEyeLeftEar and LeftEyeRightEar) have 12 degree cross angle
with tilt 6 degree first become 10 degree( -2), second become 16 degree(+4).
10-16 is much better than 12-12 for Human stereo vision( I explained it above)

 

[Serg]

LeftEyeRightEar without tilt , same 12 degree

 

[Serg]

LeftEyeLeftEar tilt 6 degree( for 250 mm) cross angle is 10( no obscuration for 250mm distance yet, it mean no obscuration for bigger observer distance too)

 

[Serg]

LeftEyeRightEar tilt 6 degree in same direction of course( for 250mm distance), cross angle become 16 degree what is much better than 12 degree but not enough for 250 mm observer distance yet ( 21 angle is necessary)

 

[Serg]

LeftRight ray. Tilt 3 degree(for 520mm observer distance) , cross angle 14 degree, not obscuration.

so this phenomena help RBC avoid main part obscuration for both eyes from distance 350 mm( 4,5 degree tilt , cross angle for LeftRightRay is 15 degree,angle distance between left eye right ear is 15 degree too. crossAngle for LeftLeftRay is 10,5 degree, bigger than enough)

ASET/IS can not exam this and give benefits for cut with such cross rays. this is one of critical ASET/IS limitations to grade new fancy cuts.

In same time it is very useful technology for below tasks:
1) If you have sample of nice cut and want cut same or find similar
a. control cutting process last stages
b. quality control for polished diamonds. ( If you have image from sample diamond you can easy compare two diamonds).
2) Rejection tool for arbitrary cut
a. To control heavy leakage better to use IS( or ASET with strong backlight is good too)
b. ASET is helpful to catch diamonds with bad attitude CoVFs distribution. For example cuts what have only one color ( green or red or blue) or cases when these colors have bad distribution in ASET image( one color is connecting to one type real facets only)

 

[strmrdr]

Date: 8/1/2009 1:02:17 AM
Author: Rhino

Date: 7/31/2009 12:56:51 PM

Author: strmrdr

34/41 at 400mm for comparison

Personally ... I enjoy how the mains light up with this combo and focal length though I''m not 100% sure how far 400mm is from my face.

~15.75 inches

 

[Garry H (Cut Nut)]

Date: 7/31/2009 4:17:03 PM
Author: Serg
dmc file for upper image

Andrey is looking into why the DiamCalc file did not upload.
Meanwhile I will try a .gem file.

And I made some movies and loaded them here

http://www.youtube.com/watch?v=9QgQk2Ieg54
http://www.youtube.com/watch?v=WpFv0c0fuqQ
http://www.youtube.com/watch?v=PnUyGVLRRIA
http://www.youtube.com/watch?v=mIKroxc-cyI
They show persistant dark zones as the stone rocks resulting from head obscuration

 

[diagem]

Date: 8/1/2009 8:24:59 AM
Author: Garry H (Cut Nut)

Date: 7/31/2009 4:17:03 PM
Author: Serg
dmc file for upper image

Andrey is looking into why the DiamCalc file did not upload.
Meanwhile I will try a .gem file.

And I made some movies and loaded them here

http://www.youtube.com/watch?v=9QgQk2Ieg54
http://www.youtube.com/watch?v=WpFv0c0fuqQ
http://www.youtube.com/watch?v=PnUyGVLRRIA
http://www.youtube.com/watch?v=mIKroxc-cyI
They show persistant dark zones as the stone rocks resulting from head obscuration

Depending in which environment you look (you show four), in the HDR it appears perfectly ok blending in with the contrast?

 

[Garry H (Cut Nut)]

Date: 8/1/2009 8:54:27 AM
Author: DiaGem

Date: 8/1/2009 8:24:59 AM
Author: Garry H (Cut Nut)

Date: 7/31/2009 4:17:03 PM
Author: Serg
dmc file for upper image

Andrey is looking into why the DiamCalc file did not upload.
Meanwhile I will try a .gem file.

And I made some movies and loaded them here

http://www.youtube.com/watch?v=9QgQk2Ieg54
http://www.youtube.com/watch?v=WpFv0c0fuqQ
http://www.youtube.com/watch?v=PnUyGVLRRIA
http://www.youtube.com/watch?v=mIKroxc-cyI
They show persistant dark zones as the stone rocks resulting from head obscuration

Depending in which environment you look (you show four), in the HDR it appears perfectly ok blending in with the contrast?

That lighting will be rather favourable to the dark zones DG
Here are the ETAS and the observer that were used

 

[diagem]

Date: 8/1/2009 9:12:04 AM
Author: Garry H (Cut Nut)

Date: 8/1/2009 8:54:27 AM
Author: DiaGem

Date: 8/1/2009 8:24:59 AM
Author: Garry H (Cut Nut)

Date: 7/31/2009 4:17:03 PM
Author: Serg
dmc file for upper image

Andrey is looking into why the DiamCalc file did not upload.
Meanwhile I will try a .gem file.

And I made some movies and loaded them here

http://www.youtube.com/watch?v=9QgQk2Ieg54
http://www.youtube.com/watch?v=WpFv0c0fuqQ
http://www.youtube.com/watch?v=PnUyGVLRRIA
http://www.youtube.com/watch?v=mIKroxc-cyI
They show persistant dark zones as the stone rocks resulting from head obscuration

Depending in which environment you look (you show four), in the HDR it appears perfectly ok blending in with the contrast?

That lighting will be rather favourable to the dark zones DG
Here are the ETAS and the observer that were used

Obviously, but thats one of the common light environment IRL.
I notice a clear visual difference between seeing how it blends right in the HDR vs the other three..., in the rest you clearly see a difference between the dark-zones under the table vs. the green-red (ASET) or red (IS) in the crown area.

 

[strmrdr]

Date: 8/1/2009 9:24:57 AM
Author: DiaGem
Obviously, but thats one of the common light environment IRL.

I notice a clear visual difference between seeing how it blends right in the HDR vs the other three..., in the rest you clearly see a difference between the dark-zones under the table vs. the green-red (ASET) or red (IS) in the crown area.

imho there isn't a huge downside to small persistent dark zones.
But if you have a huge VF that does it like a pavilion main in a round or under the table in my asscher example it is much more of a problem.
lifesize at 1ct those dark zones in the princess are tiny.

 

[diagem]

Date: 8/1/2009 10:23:43 AM
Author: strmrdr

Date: 8/1/2009 9:24:57 AM
Author: DiaGem
Obviously, but thats one of the common light environment IRL.

I notice a clear visual difference between seeing how it blends right in the HDR vs the other three..., in the rest you clearly see a difference between the dark-zones under the table vs. the green-red (ASET) or red (IS) in the crown area.

imho there isn''t a huge downside to small persistent dark zones.
But if you have a huge VF that does it like a pavilion main in a round or under the table in my asscher example it is much more of a problem.
lifesize at 1ct those dark zones in the princess are tiny.

So you are going to need more movement...., a natural part of the Diamonds environment..., movement.

 

[strmrdr]

Date: 8/1/2009 11:15:56 AM
Author: DiaGem
So you are going to need more movement...., a natural part of the Diamonds environment..., movement.

I don''t think many people would want to have to move their hand through a 15 degree ark every time they wanted to see some life to their diamond.
1-3 degrees is much more reasonable.

 

[diagem]

Date: 8/1/2009 11:40:49 AM
Author: strmrdr

Date: 8/1/2009 11:15:56 AM
Author: DiaGem
So you are going to need more movement...., a natural part of the Diamonds environment..., movement.

I don''t think many people would want to have to move their hand through a 15 degree ark every time they wanted to see some life to their diamond.
1-3 degrees is much more reasonable.

Either a Diamond or the person or the light must move to notice the life-light moving..., 15 or 3 degrees is a problem?