shape
carat
color
clarity

The amazing work of Bruce Harding; AKA Beryl

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
ChunkyCushionLover said:
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).

Sorry CCL - which page? Which grid?
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).

Sorry CCL - which page? Which grid?

Under Dead Center.
I mean I know pavilion slopes from 24.5 to 35 are going to be undesireable as well but its not explained explicitly.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
ChunkyCushionLover said:
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).

Sorry CCL - which page? Which grid?
CCL this chart is for ALL gem materials, not just diamond.
And I think the 36.75 cut off seems to work well for both quartz and diamond when a 10 degree tilt of the stone or viewers monoscopic view is used.
Almost all of Bruce's work is valid for ALL gem materials - which when you think about it - is amzing.
No?
Under Dead Center.
I mean I know pavilion slopes from 24.5 to 35 are going to be undesireable as well but its not explained explicitly.
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).

Sorry CCL - which page? Which grid?
CCL this chart is for ALL gem materials, not just diamond.
And I think the 36.75 cut off seems to work well for both quartz and diamond when a 10 degree tilt of the stone or viewers monoscopic view is used.
Almost all of Bruce's work is valid for ALL gem materials - which when you think about it - is amzing.
No?
Under Dead Center.
I mean I know pavilion slopes from 24.5 to 35 are going to be undesireable as well but its not explained explicitly.

Garry the critical angle for quartz/air is 40.49 degrees so no that cutoff won't work at all.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
ChunkyCushionLover said:
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).

Sorry CCL - which page? Which grid?
CCL this chart is for ALL gem materials, not just diamond.
And I think the 36.75 cut off seems to work well for both quartz and diamond when a 10 degree tilt of the stone or viewers monoscopic view is used.
Almost all of Bruce's work is valid for ALL gem materials - which when you think about it - is amzing.
No?
Under Dead Center.
I mean I know pavilion slopes from 24.5 to 35 are going to be undesireable as well but its not explained explicitly.

Garry the critical angle for quartz/air is 40.49 degrees so no that cutoff won't work at all.

CCL you know this is only one aspect - that of obstruction. This is a work that examines zones and type of obstruction. In many cases the RI and critical angle are not factors.
I do not have time to totally read and get inside Bruce's head.
 
  • Like
Reactions: AV_

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
ChunkyCushionLover said:
Garry H (Cut Nut) said:
http://www.gemology.ru/cut/english/faceting/
This was ground breaking work that went unrecognized for 2 or 3 decades.
Bruce was cutting and polishing a beryl in his attic late at night in the 1970's and discovered head obstruction. Being an engineer, he devised charts for each type or cause of darkness caused by our head. He made these charts for all popular gem materials.

I began communicating with Bruce over a decade ago, I think Michael Cowing may have 'discovered his work?
I met Bruce around 2001/2 and we discussed some points where we had disagreed via email - over the breaking of bread we became of the same mind. In 2004 Bruce travelled to Moscow for the first diamond cut conference. He also worked as a consultant for the AGS's cut grading system.

Of late Bruce has been collating some of his other work and sending out emails.

Garry,

I have some questions about the article are you going to be able to answer them or Bruce?
For example how come he didn't put on the grid from 24.5 - 35 (as the CA of diamond is 24.5).

Sorry CCL - which page? Which grid?
CCL this chart is for ALL gem materials, not just diamond.
And I think the 36.75 cut off seems to work well for both quartz and diamond when a 10 degree tilt of the stone or viewers monoscopic view is used.
Almost all of Bruce's work is valid for ALL gem materials - which when you think about it - is amzing.
No?
Under Dead Center.
I mean I know pavilion slopes from 24.5 to 35 are going to be undesireable as well but its not explained explicitly.

Garry the critical angle for quartz/air is 40.49 degrees so no that cutoff won't work at all.

CCL you know this is only one aspect - that of obstruction. This is a work that examines zones and type of obstruction. In many cases the RI and critical angle are not factors.

Garry,

Simply linking to an article and putting in one line of effort doesn't start a discussion.

Pavilion angles under 40 degrees will allow light to pass right through a quartz pavilion its leakage not obstruction and you should be well aware of that.

The chart later on in the paper (under materials) the suggested pavilion angle for quartz is 43 degrees with varying crown angles which makes sense given its critical angle.
 

Karl_K

Super_Ideal_Rock
Trade
Joined
Aug 4, 2008
Messages
14,685
ccl, after my wedding we can discuss this some more but critical angle does not work like you think it does in gemstones.
The obstructive angle doesn't either, pay careful attention to which angles he is talking about in the article.
It confused me for a while also, it seems simple but it is very very very deep.

see screen shot: material is diamond

criticalAngle.jpg
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Karl,

Note to you and Garry, its not what you know its how well you explain, prove, and support your statements that allows others to learn.
For the benefit of lurkers I am responding in detail here as the responses here are lacking in details and proper context.

Quartz has an RI of 1.54 that is low compared to most other precious gems (e.g. sapphire, spinel, tourmaline, topaz, tanzanite, zircon etc.), this means the pavilion mains for this material must be cut at steeper angles to avoid leakage out the bottom.
While the same methodology in Bruce's article can be applied to it, the example grids throughout the paper do not, the pavilion angles for the optimal zones have to be shifted steeper than 40.5 degrees to make any sense for this low RI material.

Experienced precision gemstone cutters(who are not cheating for weight) do not cut Quartz below its critical angle. Most cutters routinely cut the pavilion at least 1.5 degress(usually more) above the critical angle for all materials. To avoid a large and noticeable tilt window cutting well over the critical angle is better.

Being below the critical angle doesn't mean its all leakage, there are two factors that allow a stone with pavilion angles below its critical angle to return light to the viewer this applies to all materials:

1) Rays do not have to all come in through(perpendicular) to the table. If they are bent in from the crown at lower angles they can still be returned to the viewer.

2) The critical angle is the angle below which rays perpendicular to the table start to leak through the pavilion, as in they are not totally internally reflected. That doesn't mean all the intensity is lost by leakage just below the critical angle.

3) See your example below for diamond, I put the pavilion angle 0.1 degrees below the critical angle of Diamond to show the leakage through the pavilion beginning (14% lost). The ASET still shows these regions can be lit by low angle light but some intensity will be lost.

BelowCriticalAngleofDiamond.jpg
 
  • Like
Reactions: AV_

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Karl_K said:
ccl, after my wedding we can discuss this some more but critical angle does not work like you think it does in gemstones.
The obstructive angle doesn't either, pay careful attention to which angles he is talking about in the article.
It confused me for a while also, it seems simple but it is very very very deep.

see screen shot: material is diamond

criticalAngle.jpg

Congratulations and have a great wedding btw. This stuff is much less important than that. We'll continue after the honeymoon ;))
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Garry H (Cut Nut) said:
CCL you know this is only one aspect - that of obstruction. This is a work that examines zones and type of obstruction. In many cases the RI and critical angle are not factors.

Garry,

Perhaps when you have time you could link to the specific sections in Bruce's article that relate to obstruction and explain with a DC ray trace or two correlated with ASET. I think that would help more posters focus on the importance of the article and how to apply and understand it.

Thanks,
CCL
 

beryl

Shiny_Rock
Joined
Nov 6, 2003
Messages
288
I was making a nice thorough reply when it disappeared from my screen. No time to do it again. Hopefully I will find it later.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
beryl said:
I was making a nice thorough reply when it disappeared from my screen. No time to do it again. Hopefully I will find it later.
Hi Bruce, sorry you have a problem. Some times its a good idea to write up in word and then you have a saved copy.

CCL asked what the RI was in Faceting limits?
I think you mentioned 1.8 to 1.9?
I can not see where it is mentioned in the article?
 

beryl

Shiny_Rock
Joined
Nov 6, 2003
Messages
288
The ENTIRE ARTICLE is about head obstruction. It was written from the viewpoint of a colored-stone cutter and included diamonds only to complete the spectrum.
The Russian reproduction listed it under ‘Diamonds’ and thereby caused confusion. The charts shown during the text are for RI= 1.67 because it served the purpose well.
In the original GIA article all specific charts were shown on one page; since pavilion slopes less than 34° for RI >1.8 were absurd, higher RI charts were truncated at this point to better-fit them on the page (you can see that in the GIA article).
This started when I cut a garnet at 40/40 per Sinkankas’ recommendation. Then I sat in a chair with a reading lamp above and behind me to admire my work. It was pretty until I moved it close to me and it went dark. By tracing the reflections with a pin point, I found the cause to be obstruction of the light by my head.
For many years I had tried to define proportions of a ‘good’ gem unsuccessfully. When this happened I decided to approach the subject from the other end – by indicating all the ‘bad’ gems on a chart. To verify my results I noted all of the proportions that were recommended as ‘best’ by historical evolution. I was pleased to find that they all fell outside these ‘bad’ zones (except Sinkankas, which was not historical).
The surprising thing, however, was that these points all fell near the edges of the upper obstruction zone. Garry explained that 25 years later because it caused light:dark contrast between the mains and break facets, which is appealing to the eye.
At that time (2000), Garry was trying to tell people about a relationship between pavilion and crown slopes which gave good results. He was ridiculed until my article was brought to bear (via Mike Cowing) and proved his point. The rest is history.
The original GIA article is now available via Internet at GIA archives.
The 'amazing' thing about this article is that it was ever published. We owe gratitude to Richard Liddicoat, then Pres. of GIA, who published it despite objections by GIA's expert advisors. One said 'the viewer's head can have no place in a scientific study. Much flak ensued at GIA and they removed cut proportion grading from their course.
My best work in this field was in a talk I gave at Antwerp in 2005, but primarily of interest to colored-stone people.
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
beryl said:
The ENTIRE ARTICLE is about head obstruction. It was written from the viewpoint of a colored-stone cutter and included diamonds only to complete the spectrum.
The Russian reproduction listed it under ‘Diamonds’ and thereby caused confusion. The charts shown during the text are for RI= 1.67 because it served the purpose well.
In the original GIA article all specific charts were shown on one page; since pavilion slopes less than 34° for RI >1.8 were absurd, higher RI charts were truncated at this point to better-fit them on the page (you can see that in the GIA article).
This started when I cut a garnet at 40/40 per Sinkankas’ recommendation. Then I sat in a chair with a reading lamp above and behind me to admire my work. It was pretty until I moved it close to me and it went dark. By tracing the reflections with a pin point, I found the cause to be obstruction of the light by my head.
For many years I had tried to define proportions of a ‘good’ gem unsuccessfully. When this happened I decided to approach the subject from the other end – by indicating all the ‘bad’ gems on a chart. To verify my results I noted all of the proportions that were recommended as ‘best’ by historical evolution. I was pleased to find that they all fell outside these ‘bad’ zones (except Sinkankas, which was not historical).
The surprising thing, however, was that these points all fell near the edges of the upper obstruction zone. Garry explained that 25 years later because it caused light:dark contrast between the mains and break facets, which is appealing to the eye.
At that time (2000), Garry was trying to tell people about a relationship between pavilion and crown slopes which gave good results. He was ridiculed until my article was brought to bear (via Mike Cowing) and proved his point. The rest is history.
The original GIA article is now available via Internet at GIA archives.
The 'amazing' thing about this article is that it was ever published. We owe gratitude to Richard Liddicoat, then Pres. of GIA, who published it despite objections by GIA's expert advisors. One said 'the viewer's head can have no place in a scientific study. Much flak ensued at GIA and they removed cut proportion grading from their course.
My best work in this field was in a talk I gave at Antwerp in 2005, but primarily of interest to colored-stone people.

Thanks you Bruce it was an excellent article. I found the original published text in the Fall 1975 G&G
http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/fall-1975.pdf.

I beleive your work is applicable to all materials and would like to see images or commentary from your 2005 talk, due to cheaper rough cutter's can be more creative with colored stones, but I beleive the designs and principals for colored stones have great relevance to future diamond design as well.

One of the first things that jumped out at me was the table to table rays framework where you consider the viewer's head as a cone of obstruction of only 10 degrees.

This is in contrast to Sassian's publication and foundations of AGSL's ASET http://www.agslab.com/spie/spie_lo_res.pdf which considers the viewer seeing their own reflections or blocking light from an angular range of 30 degrees.

At viewing of one foot is the viewer really only blocking 10 degrees? If so the adjusted ASET 10 image of a Tolk Round diamond would look like this.

TolkowskyASET10Fixed.jpg
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Whereas the classical Tolk Round looks like this with a cone of obstruction of 30 degrees. How close does the viewer need to be to see the contrast in the arrows under the table in the faceup position?

TolkowskyASET30.jpg
 
  • Like
Reactions: AV_

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
This slide validates your table to table rays calculation for RI=1.67 material.

The virtual facets under the table mains in a tolk round gather light right around 85 degrees for RI=1.67 material.
PA = 40.75 CA= 34.5

ASETImagesRI167.jpg

However for diamond RI=2.418 these same virtual facets gather light from around 78.5 degrees.
 
  • Like
Reactions: AV_

beryl

Shiny_Rock
Joined
Nov 6, 2003
Messages
288
. The 10° angle approximated measurements made hastily before a mirror with a ruler; no attempt at precision - just a handy base for plotting the charts. Actually, the shaded area is not distinct, as I have shown it; it should be graduated for various angles of obstruction, depending on viewing distance and size of viewer's head (or hair or hat).
. Note, from Fig.1 (or 2) of the article, that the angle is from one eye to the ear on the same side. The attached illustration shows a later analysis I did for studying stereo images. The total angle of head obstruction here is 12.4° + 2 X 8.9° = 30.2° from ear-to-ear; perhaps that is what Jose Sassian had in mind; I never inquired and am unaware of his publication.
. The original Russian studies (1998) had a viewer with one eye in the middle of the head, so I don't know how they measured it. Anton Vasiliev of LAL, who was on that team, had a copy of my article and made it known to the others. He published an article about this (Poland, 1995, ‘Selecting Facet Slope Angles’, Acta Universitatis Wratislaviensis, 1607, 143-6, later reproduced in Russian at www.gemology.ru). He also wrote an article for Russian Gemmological Bulletin (5) 2002 No.2, p.33-41, "Optimizing Faceting for Beauty", in which he modified the charts to include a tilt angle between the viewer's eye and the axis of the stone; this has been re-published in British Gemmological Journal, Vol.29 No.1, January 2004, p.25-36. (I can email you a copy ).
. The important fact is that the historically evolved ‘best’ cuts are near the edges of the head obstruction zone, which is good, and, by Garry’s observation, cause light:dark contrast with the nearby break facets. I think all of this implies good credibility for the method of analysis. It is also important to note (as Michael Cowing does) that all of this significance comes from a 2-dimensional analysis of rays only in a central plane !!!
. I will send you a copy of my 2005 Antwerp presentation when I know your email address.

stereo.GIF
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
beryl said:
. The 10° angle approximated measurements made hastily before a mirror with a ruler; no attempt at precision - just a handy base for plotting the charts. Actually, the shaded area is not distinct, as I have shown it; it should be graduated for various angles of obstruction, depending on viewing distance and size of viewer's head (or hair or hat).
. Note, from Fig.1 (or 2) of the article, that the angle is from one eye to the ear on the same side. The attached illustration shows a later analysis I did for studying stereo images. The total angle of head obstruction here is 12.4° + 2 X 8.9° = 30.2° from ear-to-ear; perhaps that is what Jose Sassian had in mind; I never inquired and am unaware of his publication.
. The original Russian studies (1998) had a viewer with one eye in the middle of the head, so I don't know how they measured it. Anton Vasiliev of LAL, who was on that team, had a copy of my article and made it known to the others. He published an article about this (Poland, 1995, ‘Selecting Facet Slope Angles’, Acta Universitatis Wratislaviensis, 1607, 143-6, later reproduced in Russian at www.gemology.ru). He also wrote an article for Russian Gemmological Bulletin (5) 2002 No.2, p.33-41, "Optimizing Faceting for Beauty", in which he modified the charts to include a tilt angle between the viewer's eye and the axis of the stone; this has been re-published in British Gemmological Journal, Vol.29 No.1, January 2004, p.25-36. (I can email you a copy ).
. The important fact is that the historically evolved ‘best’ cuts are near the edges of the head obstruction zone, which is good, and, by Garry’s observation, cause light:dark contrast with the nearby break facets. I think all of this implies good credibility for the method of analysis. It is also important to note (as Michael Cowing does) that all of this significance comes from a 2-dimensional analysis of rays only in a central plane !!!
. I will send you a copy of my 2005 Antwerp presentation when I know your email address.

You can get my e-mail from Garry or from Admin, I know I'm not allowed to post it in the forums.

Your input and the references are much appreciated.

As you said the viewing distance is taken into consideration, I beleive AGSL used 8 inches, the idealcscope is 10 inches (Garry is that right?).

Then their is the issue of Cyclops versus Stereovision, in any case I'd like to take a look at the references you listed above and your input.

Best Regards,
CCL
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
Sorry for not responding earlier - been a lot happening here.

Bruce I think 30 degrees is a bit much for at least 2 reasons:

1. Light coming from above the head makes an angle of about 22 degrees - and that is to both eyes.

2. If either eye sees a flash from the light coming from 8.9 or 10 degrees then a flash is recorded in the mind. Of course there is nearly twice the chance if you use 30 degrees as the bench mark - but really the best value lies somewhere between.

Ideal-scope lens / darkness is about 25 degrees for those reasons.

The actual reason AGS used 30 degrees was because the US military 'human' standard vision difference is about 8 inches. I think that is too close for most obesrvations.
Sergey usually prefers 14 inches (35cm).
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459

beryl

Shiny_Rock
Joined
Nov 6, 2003
Messages
288
CCL:
. In my response of Oct 29, I mentioned an article by Anton Vasiliev, "Selection of Facet Slopes", which had been published in Poland in 1995 and later reproduced at the Russian website. Today I was there and noticed that it is no longer listed with other articles. However, it is there, listed in the bibliography of "Rainbow in a Colorless Gem" and I found it intact by clicking on that reference:
. http://www.gemology.ru/cut/english/vasiliev/vas1.htm
. My name is spelled wrong in the bibliography but you should see how it's spelled in Russian; they have no character for the sound 'H'!
 

Serg

Ideal_Rock
Trade
Joined
Mar 21, 2002
Messages
2,626
beryl|1289856154|2767098 said:
CCL:
. In my response of Oct 29, I mentioned an article by Anton Vasiliev, "Selection of Facet Slopes", which had been published in Poland in 1995 and later reproduced at the Russian website. Today I was there and noticed that it is no longer listed with other articles. However, it is there, listed in the bibliography of "Rainbow in a Colorless Gem" and I found it intact by clicking on that reference:
. http://www.gemology.ru/cut/english/vasiliev/vas1.htm
. My name is spelled wrong in the bibliography but you should see how it's spelled in Russian; they have no character for the sound 'H'!

Hi Bruce,

we do not change and update www.gemology.ru last several years

You can find full list here http://www.octonus.com/oct/projects/

Screen shot 2010-11-30 at 10.40.15 PM.png
 

ChunkyCushionLover

Ideal_Rock
Joined
Jun 21, 2009
Messages
2,463
Thanks for the update Bruce. When I have more time I will look into this further.
 

beryl

Shiny_Rock
Joined
Nov 6, 2003
Messages
288
Sergey:
. Thank you for this list. There are many things I have missed in recent years; I look forward to reading these. At 1st IDCC conference I promised to participate in 'Cut Group' but did not know where to find it, nor did I know of the 2nd IDCC conference in 2009. Often it is assumed that people know things when they don't = missed opportunities at both ends. Good products often do not sell because they are not advertised well; Olga knows that. Say 'Hi' to Olga.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,459
beryl|1291212621|2784033 said:
Sergey:
. Thank you for this list. There are many things I have missed in recent years; I look forward to reading these. At 1st IDCC conference I promised to participate in 'Cut Group' but did not know where to find it, nor did I know of the 2nd IDCC conference in 2009. Often it is assumed that people know things when they don't = missed opportunities at both ends. Good products often do not sell because they are not advertised well; Olga knows that. Say 'Hi' to Olga.
Bruce we pulled the plug on IDCC2 because of the financial crisis
 

AV_

Ideal_Rock
Joined
Aug 5, 2018
Messages
3,889
This thread is still indispensible

- for its intended purpose & for reading videos of diamonds too.
 

Karl_K

Super_Ideal_Rock
Trade
Joined
Aug 4, 2008
Messages
14,685
I used things he taught me in designing the Octavia.
He was a good man, smart and generous with his time explaining things.
RIP
 
Be a part of the community Get 3 HCA Results
Top