GIA Diamond Cut Grading: Problems with Diamond Dock

[strmrdr]

I noticed something in the CZ pictures.
The girdle area looks worse on the bad cz in the DD than the other images.
Is the problem with DD and painted girdles the angle of the light striking the girdles, traditional girdles are returning more light when lit at that angle??
It sure looks that way to me when taken to the extreme of the bad cz.
Id like to see more images!

 

[JohnQuixote]

Garry, thank you for the overview. While diamonds are not about a simple static view, the comparison photos are helpful in illustrating what''s been discussed here and in other threads.

Date: 3/16/2006 2:43:19 AM
Author: Garry H (Cut Nut)

Rhino, Sergey has discussed an experiment. Line the walls and base of Diamond Dock(r) with white paper, conduct a survey with a big range of diamonds, then line it with black paper, do the same again and finally do the survey with the GIA Gray - have I got it right Sergey?

This would show how the various backgrounds and eye adaption can influence the results.

I''m interested in the results of that proposal if Rhino is agreeable to it. I also believe the suggestion for mounting the stones rather then only having them observed in a tray is valid. Is there a scientific reason that analysis in both trays & temporary settings would not be valid?

 

[JohnQuixote]

Date: 3/16/2006 9:33:45 AM
Author: strmrdr
I noticed something in the CZ pictures.
The girdle area looks worse on the bad cz in the DD than the other images.
Is the problem with DD and painted girdles the angle of the light striking the girdles, traditional girdles are returning more light when lit at that angle??
It sure looks that way to me when taken to the extreme of the bad cz.
Id like to see more images!

The girdle area looks pretty bad in this stock photo as well (upper = stock, lower = in DD). What is surprising to me is how poor the well cut CZ looks in the DD.

 

[strmrdr]

John,
compare both of them to the on finger shots.
The black background in the Garry''s stock photo also exagerates the difference compared to the hand shots.
I could be on the wrong track but id like to see it looked into.
If I could run DC, id run some traces into the girdles when the "diamond" is at an angle and compare the results between the two types.

 

[Rhino]

Hi Garry, Sergey, strm, tars, and all,

Just getting ready for my late day here and thought I''d check in on this thread before leaving for work. Let me thank you for keeping the discussion intellectual as we all explore these issues in greater depth together. I agree with Belle in that a photograph, even an excellently done photograph is still not a final arbitrator unless of course you are a cycloptic colleague.

She also notes however that a good photograph can show critical elements which is also true. Thank you for that input belle. I see I must read that article before continuing here.

Pondering the issues that have arrised on these boards lately I have taken a series of photographs in varying environments which I would like to garner your input on to see if you can observe, in the photographs, the optical phenomena I and the consumers we surveyed observe with our eyes in stereo vision. I realize this may be a challenging experiment, but I am of course open to your input and always open to listening to reason.

Kind regards,

 

[JohnQuixote]

Date: 3/16/2006 2:25:20 AM
Author: Serg
re:And - conversely - it is possible to design a diamond that will max out the metric of any such evaluative environment.

John,

Such statement is not obviously at least( Even could be wrong) . I do not know how it could be done. You can optimize limited number parameters of any cut for fixed ilumination. But How will you find BEST TYPE of CUT for this illumination? How do you know what is maximum?

Serg,

I was thinking specifically of Brilliancescope (and Isee2) where a manufacturer can identify specific configurations that perform well in the metric and replicate them for that purpose. It's from an old discussion I had with Marty (2004 thread).

Date: 11/27/2004 3:52:38 PM
Author: adamasgem
2) Knowing the way the BS scope lighting works, you can probably design a 'cut' to maximize its returned 'performance' metric.

There is a funny correlation here. At the time of that thread, Brilliancescope was being pitched as decisive by some people. Others maintained that any single view cannot be considered absolute. It was an ongoing debate - the conversations got pretty extreme. Since that time the PS community has come to view BS in what I consider a more reasonable perspective.

I believe all ways of looking at diamonds, including Brilliancescope - and now DD - can provide us with useful info. The key is for us to remain calm - not hype or disregard them completely... and keep them in perspective.

 

[strmrdr]

te:[/b] 3/16/2006 10:12:50 AM
Author: JohnQuixote
The key is for us to remain calm - not hype or disregard them completely..and keep them in perspective.

[/quote]
Well said.
Im trying to get perspective on the DD and the GIA system and the way the threads have been going thats impossible which is why im frustrated.
It is also creating confusion for those that are trying to follow along.

 

[adamasgem]

Date: 3/16/2006 9:39:11 AM
Author: JohnQuixote
Garry, thank you for the overview. While diamonds are not about a simple static view, the comparison photos are helpful in illustrating what's been discussed here and in other threads.

Date: 3/16/2006 2:43:19 AM
Author: Garry H (Cut Nut)

Rhino, Sergey has discussed an experiment. Line the walls and base of Diamond Dock(r) with white paper, conduct a survey with a big range of diamonds, then line it with black paper, do the same again and finally do the survey with the GIA Gray - have I got it right Sergey?

This would show how the various backgrounds and eye adaption can influence the results.

I'm interested in the results of that proposal if Rhino is agreeable to it. I also believe the suggestion for mounting the stones rather then only having them observed in a tray is valid. Is there a scientific reason that analysis in both trays & temporary settings would not be valid?

John: RE Mounting: It is a much more difficult problem relative to human perception, let alone modeling the effects. Mountings vary in their reflectivity based on type and color of metal, number of prongs, the prong polish (finish) backgound reflection into the pavilion due to illumination. placement of prongs on stone will effect the patterning seen, etc, etc, etc

Human visual perception and color vision is a complex interaction between the reflectivity (absorption) of the test item, the illumination spectra, the intensity of the illumination, the immediate background (spectra and relative intensity) the "surround" (spectra, intensity), scotoptic or photopic adaptation of the viewer as well as his color vision, etc etc etc..

I had six "try" mounts made out of different colors of gold and platiunim with different types of prongs, including channes mount by have a stone set in the mounting, and then the mounting slit from the shank into the bottom of the prong.
I looked at the relative spectra I obtained on a series of each of my master stones, all being about the same 1/3ct size, and found significant differences, all consistent mounting to mounting.

The entire problem is highly NON LINEAR also, so it makes for a difficult analytic task.. with a lot with "interpretation" or "mis interpretation" problems with the "results".. a big task to do it correctly, and beyond the resourses of anyone here, I believe.



By the way Sergey/Leonid/Garry Excellent summary of the problems with DD

 

[WinkHPD]

A huge thank you to Gary for posting pictures that back up my initial perception of the DD, that it does in fact take horribly cut diamonds and make them look like pretty good diamonds. I have four of the sets that Gary has made and they are invaluable in showing people why they want to have a well cut diamond. It is a LOT cheaper to own a poorly cut CZ to use as an example than a poorly cut diamond, although I have a little .33ct H-SI1 that is itself pretty ugly. Cut properly it should weigh less than .25ct, but at least then it would be attractinve...

I show it next to a premium cut for cut comparrisons, then show the premium next to the H&A. MUCH less difference between a premium and an ideal than many might think, but there is definitely a difference.

Wink

 

[JohnQuixote]

Date: 3/16/2006 1:29:45 PM
Author: adamasgem

John: RE Mounting: It is a much more difficult problem relative to human perception, let alone modeling the effects. Mountings vary in their reflectivity based on type and color of metal, number of prongs, the prong polish (finish) backgound reflection into the pavilion due to illumination. placement of prongs on stone will effect the patterning seen, etc, etc, etc

Human visual perception and color vision is a complex interaction between the reflectivity (absorption) of the test item, the illumination spectra, the intensity of the illumination, the immediate background (spectra and relative intensity) the 'surround' (spectra, intensity), scotoptic or photopic adaptation of the viewer as well as his color vision, etc etc etc..

I had six 'try' mounts made out of different colors of gold and platiunim with different types of prongs, including channes mount by have a stone set in the mounting, and then the mounting slit from the shank into the bottom of the prong.
I looked at the relative spectra I obtained on a series of each of my master stones, all being about the same 1/3ct size, and found significant differences, all consistent mounting to mounting.

The entire problem is highly NON LINEAR also, so it makes for a difficult analytic task.. with a lot with 'interpretation' or 'mis interpretation' problems with the 'results'.. a big task to do it correctly, and beyond the resourses of anyone here, I believe.

By the way Sergey/Leonid/Garry Excellent summary of the problems with DD

Marty, thanks for elaborating. So, the main issue is that mountings would introduce yet another layer of variability (and taste). Understandable, if frustrating, since most diamonds are viewed in settings.

The first post here and the journal article are well presented technical and graphic explanations of what you/Serg have expressed about the drawbacks of the DD environment. That said, I'm interested in understanding more about what it can tell us that is useful.

 

[JohnQuixote]

Date: 3/16/2006 10:42:27 AM
Author: strmrdr

Date: 3/16/2006 10:12:50 AM
Author: JohnQuixote
The key is for us to remain calm - not hype or disregard them completely..and keep them in perspective.

Well said.
Im trying to get perspective on the DD and the GIA system and the way the threads have been going thats impossible which is why im frustrated.
It is also creating confusion for those that are trying to follow along.

Yeah, those trees keep getting in the way as we try to map out this forest.

The critical environment is natural for something new. It''s easy to get caught up in the momentum, no matter which ground you''re defending. Actually, not too long ago, I was the one encouraging patience as we were pre-judging the GIA system (somewhere around here)... The system is not quite the refined one many of us hoped for/expressed, but at least there is one in place.

Unless upstream manufacture shifts significantly to steep/deep (ergo steeper/deeper) I still feel consumers are better served by a GIA with a cut grading system over a GIA without one. Yes, there are issues to be worked out, but the overall awareness generated by a lab of their stature implementing this change is very positive (there''s that forest).

 

[Rhino]

Date: 3/16/2006 10:12:50 AM
Author: JohnQuixote

Date: 3/16/2006 2:25:20 AM
Author: Serg
re:And - conversely - it is possible to design a diamond that will max out the metric of any such evaluative environment.

John,

Such statement is not obviously at least( Even could be wrong) . I do not know how it could be done. You can optimize limited number parameters of any cut for fixed ilumination. But How will you find BEST TYPE of CUT for this illumination? How do you know what is maximum?

Serg,

I was thinking specifically of Brilliancescope (and Isee2) where a manufacturer can identify specific configurations that perform well in the metric and replicate them for that purpose. It''s from an old discussion I had with Marty (2004 thread).

Date: 11/27/2004 3:52:38 PM
Author: adamasgem

2) Knowing the way the BS scope lighting works, you can probably design a ''cut'' to maximize its returned ''performance'' metric.

There is a funny correlation here. At the time of that thread, Brilliancescope was being pitched as decisive by some people. Others maintained that any single view cannot be considered absolute. It was an ongoing debate - the conversations got pretty extreme. Since that time the PS community has come to view BS in what I consider a more reasonable perspective.

I believe all ways of looking at diamonds, including Brilliancescope - and now DD - can provide us with useful info. The key is for us to remain calm - not hype or disregard them completely... and keep them in perspective.

Amen to this. I had mentioned in the other thread but will also reiterate here too ... while I am having fun experimenting with the DiamondDock and find excellent corellations between its views and daylighting environments, neither I nor GIA says it is the only environment in which these comparisons can be drawn or made.

Here is a photograph I''ve taken under it of 2 ideal H&A stones except one girdle is classic and one is dug out.

Not only can one see these differences with their eyes but it''s easy for me to photograph as well. I will say this though ... the photograph seems to be a little more dramatic since it is a static image and one can stare at it. When you''re rocking and tilting the diamonds it isn''t as obvious but it is still notable.

Seeing these kind of differences are helping me to better understand the logic behind their system. It is interesting study.

Hope this helps.

 

[adamasgem]

Date: 3/16/2006 9:43:52 PM
Author: Rhino

Here is a photograph I''ve taken under it of 2 ideal H&A stones except one girdle is classic and one is dug out.

Not only can one see these differences with their eyes but it''s easy for me to photograph as well. I will say this though ... the photograph seems to be a little more dramatic since it is a static image and one can stare at it. When you''re rocking and tilting the diamonds it isn''t as obvious but it is still notable.

Seeing these kind of differences are helping me to better understand the logic behind their system. It is interesting study.

Hope this helps.

Rhino, as a suggestion, you might annotate which stone is which on the photo to make it clearer for the general consumer.

Also, how about photos with just the LED lights on to show the fire effectin the DD.

I suggest that you also put a couple of pencil marks on the DD to attempt to position the tray and stones at the same X,Y point relative to the LED''s otherwise you WILL get different perspectives every time you do it. You can take a single stone and move it ever so slightly and get a completely different picture, so watch out about jumping to any conclusions

When I developed the Fire Performance Scope, using a controlled methodolgy which resulted in over 5000 white light sources, a miniscule rotation of the stone about its table to culet axis (via a built in rotator tray), the rotation relative to the 5000+ light sources, would cause a particular facet to light up an entirely different color...

So my conclusion is that trying to do a repeatable quanitative direct comparison with two stones and only 12 "point source" LEDS, is also frought with problems.

One collimated source, may be more quantitatively repeatable, but not a good overall measure of fire performance.

 

[Serg]

re:Here is a photograph I''ve taken under it of 2 ideal H&A stones except one girdle is classic and one is dug out.

Rhino, "dug out " produce big leakage in crown girdle facet ( at least for parameters near Tolkowsky. I am not sure about all type combination)
Such diamonds are bad in most reasonable light conditions( DD GIA is reasonable but not correct for cut grading)

in Opposite "painted''( 1 click and right star facets) is not bad.

GIA penalty "dug out " and "painted'' by same (one) rule. Penalty does not depends from type girdle and value of "painted'' and "dug out " .
It is GIA mistake.

 

[Serg]

BTW,

Rhino, On your nice photo even nice diamond is semi( or quarter ) dead. Even nice diamond can not work completely in DD GIA.

It is bad sign.

I think it is possible to develop fancy cut which will much better in DD GIA than any other round .( But this fancy will not nice in consumer conditions)

It is really hard task( direct tasks) , but is possible. I will need help from volunteers in winter 2006 to develop such fancy cut.

 

[Serg]

Date: 3/16/2006 10:12:50 AM
Author: JohnQuixote

Date: 3/16/2006 2:25:20 AM
Author: Serg
re:And - conversely - it is possible to design a diamond that will max out the metric of any such evaluative environment.

John,

Such statement is not obviously at least( Even could be wrong) . I do not know how it could be done. You can optimize limited number parameters of any cut for fixed ilumination. But How will you find BEST TYPE of CUT for this illumination? How do you know what is maximum?

Serg,

I was thinking specifically of Brilliancescope (and Isee2) where a manufacturer can identify specific configurations that perform well in the metric and replicate them for that purpose. It''s from an old discussion I had with Marty (2004 thread).

Date: 11/27/2004 3:52:38 PM
Author: adamasgem

2) Knowing the way the BS scope lighting works, you can probably design a ''cut'' to maximize its returned ''performance'' metric.

There is a funny correlation here. At the time of that thread, Brilliancescope was being pitched as decisive by some people. Others maintained that any single view cannot be considered absolute. It was an ongoing debate - the conversations got pretty extreme. Since that time the PS community has come to view BS in what I consider a more reasonable perspective.

I believe all ways of looking at diamonds, including Brilliancescope - and now DD - can provide us with useful info. The key is for us to remain calm - not hype or disregard them completely... and keep them in perspective.

John,

Marty wrote : "you can probably design a ''cut'' to maximize " . It is correct( key words probably and maximize ( not maximum). ANd for BS such work is much more easy than for arbitrary light scheme.

You wrote: "And - conversely - it is possible to design a diamond that will max out the metric of any such evaluative environment". I do not know How It can be done
THis is importnant difference

 

[Garry H (Cut Nut)]

Date: 3/17/2006 3:37:34 AM
Author: Serg

BTW,

Rhino, On your nice photo even nice diamond is semi( or quarter ) dead. Even nice diamond can not work completely in DD GIA.

It is bad sign.

I think it is possible to develop fancy cut which will much better in DD GIA than any other round .( But this fancy will not nice in consumer conditions)

It is really hard task( direct tasks) , but is possible. I will need help from volunteers in winter 2006 to develop such fancy cut.

In hong Kong I asked Tom Moses how they were progressing with fancy cut grading.
He looked blank for a few seconds, and then said "We have not done much...er I think...I have not had much to do wwith the cut team lately - been very busy...."

Sergey I do not think GIA will grade your better cut

 

[Serg]

re:Sergey I do not think GIA will grade your better cut

Garry,

I do not need it. My task to do GIA mistake obvious for consumers

 

[strmrdr]

If someone comes up with an accurate DC light scheme that duplicates the DD when I get my windows computer back up next week Id be very interested in doing some testing to see which shapes and angles work best under it.
This sounds like something that val and belle would be interested in also.

 

[Garry H (Cut Nut)]

I modelled something like it a couple of months ago - but not easy with round lights etc

 

[dhog]

Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye''s playing
tricks on me again.

 

[Serg]

Date: 3/17/2006 2:33:38 PM
Author: dhog
Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye''s playing
tricks on me again.

Dhog, Thanks. I see it now too

I think it is not important for this case, but
Rhino,
Please do not publish photomontage without notification.

 

[dhog]

Thank you Sergey and Gary for the research
and your best interests for consumers.

 

[Garry H (Cut Nut)]

Date: 3/17/2006 2:47:26 PM
Author: Serg

Date: 3/17/2006 2:33:38 PM
Author: dhog
Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye''s playing
tricks on me again.

Dhog, Thanks. I see it now too

I think it is not important for this case, but
Rhino,
Please do not publish photomontage without notification.

It is difficult to take these photo''s so that both stones are directly face on to the camera lens and also face the the lights.

Another issue is the size, color and distance of the camera lens to the stones.

Rhino please describe this or take photo''s
My photo''s were taken with a small matt silver Canon Ixus http://www.canon.com.au/images/big_products/ixus_40_front%20small.jpg with my hands also partially in the lighting.
This is probably adding less darkness to the images than Jonathons huge camera I have seen at vegas.

 

[belle]

Date: 3/17/2006 2:33:38 PM
Author: dhog
Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye''s playing
tricks on me again.

thanks for pointing that out dhog.
what harm is there in a little cut and paste? matching up two different photos and declaring it one...what''s the big deal?
surely there is a reason for going through the trouble of trying to perfectly match up two different photos and calling them one original other than differences in lighting.

 

[scotch]

Date: 3/17/2006 3:39:33 PM
Author: belle

Date: 3/17/2006 2:33:38 PM
Author: dhog
Rhino

this is again from a consumers point of view

the photo you posted above looks to me to
have 2 different light sources from the angles
that I can see.

I submit this for all P/S members to look close
in the middle of the photo and then slowly look
up to the top.

is this what I think it is or is it my eye''s playing
tricks on me again.

thanks for pointing that out dhog.
what harm is there in a little cut and paste? matching up two different photos and declaring it one...what''s the big deal?
surely there is a reason for going through the trouble of trying to perfectly match up two different photos and calling them one original other than differences in lighting.

I would not necessarily assume any ill intention. Jonathan may just have tried to photograph both stones in the exact same position.

Scotch

 

[dhog]

Date: 3/17/2006 4:10:18 PM
Author: scotch

I would not necessarily assume any ill intention. Jonathan may just have tried to photograph both stones in the exact same position.


Scotch

nobody assumed anything

since the jury is still out it is one of the
facts needed to make up your own mind.

if you would read this thread you would see
that the claim has been made that this theory
is easy too
PHOTOGRAPH



Please keep this thread on track and read between the /s

 

[scotch]

Date: 3/17/2006 4:58:08 PM
Author: dhog

Date: 3/17/2006 4:10:18 PM
Author: scotch

I would not necessarily assume any ill intention. Jonathan may just have tried to photograph both stones in the exact same position.


Scotch

nobody assumed anything

since the jury is still out it is one of the
facts needed to make up your own mind.

if you would read this thread you would see
that the claim has been made that this theory
is easy too
PHOTOGRAPH



Please keep this thread on track and read between the /s

Easy tiger....
I would hope you heed your own good advice.

Scotch

 

[Rhino]

Date: 3/17/2006 12:55:12 AM
Author: adamasgem

Rhino, as a suggestion, you might annotate which stone is which on the photo to make it clearer for the general consumer.

My apologies. For clarification the diamond on the left has the classic girdle and the diamond on the right has the dug out girdle. I can repost it with text if you''d like.

Also, how about photos with just the LED lights on to show the fire effectin the DD.

Fire is a little tougher to capture however he''s a shot I just snapped off. In the pic below the diamond with the digging is on the right as in the photo above.

I suggest that you also put a couple of pencil marks on the DD to attempt to position the tray and stones at the same X,Y point relative to the LED''s otherwise you WILL get different perspectives every time you do it. You can take a single stone and move it ever so slightly and get a completely different picture, so watch out about jumping to any conclusions

I hear ya ... haha ... I snapped off the shot before reading this paragraph so this one will have to do for now. I hear what you''re saying though. Fire is best seen than photographed me thinks. I''m about to cut out of work for the day but thought I''d try and catch up here.

Kind regards,

 

[Rhino]

Hi Sergey,

Date: 3/17/2006 3:28:47 AM
Author: Serg

re:Here is a photograph I''ve taken under it of 2 ideal H&A stones except one girdle is classic and one is dug out.

Rhino, ''dug out '' produce big leakage in crown girdle facet ( at least for parameters near Tolkowsky. I am not sure about all type combination)
Such diamonds are bad in most reasonable light conditions( DD GIA is reasonable but not correct for cut grading)

in Opposite ''painted''( 1 click and right star facets) is not bad.

GIA penalty ''dug out '' and ''painted'' by same (one) rule. Penalty does not depends from type girdle and value of ''painted'' and ''dug out '' .
It is GIA mistake.

Attached in the below graphic is the same stones along with their ASET images. Interestingly the ASET image explains the darkness we can observe in the darker stone of the 2 as it is drawing more light from the hemisphere than from above. Similar results with painting as well, also confirmed by ASET. My studies into this with the ASET have been a hoot. I love the ASET!

As you noted Serg, this difference can be seen in common daylight environments as it can also be done in the diamonddock as well. I like it because it provides a consistent viewing environment wherein a layman can observe these differences as well.

BTW the dug out stone has 34.0 crown angles, 40.9 pavilion angles, 56.2 table, 77% lower half length and 55% stars.

Kind regards,