Diamond Cut Calculator--One Never Discussed?

[Mara]

Found this a few minutes ago. It looks very interesting!! I''d be interested to see some diamonds plugged into it and see what it says on people''s stones.

Experts...any comments?

http://www.jewellerycatalogue.co.uk/diamonds/diamond_analysis.php?

 

[trichrome]

I just tried it...

"very good" in each and very category.

Trichrome.

 

[Garry H (Cut Nut)]

Interesting to me because if they wish to use it for business purposes in USA then it contravene's my pending HCA patent.

 

[Mara]

double post.

 

[Mara]

My stone scored VG across most categories, with brilliance only as good (funny cuz my stone is a BIC! and is very white brilliant looking) and crown angle and girdle as good--which makes sense because my crown angle is very shallow and the girdle is a tad thin to be with such a shallow angle. So it caught the areas which may need to be flagged (except for brilliance).

Not bad for another tool/aid just randomly found!

 

[pqcollectibles]

Very interesting, Mara!

Mine did come out a bit odd tho.

The program recalculated my Crown Angle off by one degree. The Cert reads 34.6 degrees and the UK program "calculated" it from Crown % at 33.6 degrees.

Everything came out Very Good except Distortion, which it said was/is Deep. What is Distortion??? And, what does Deep mean in relation to Distortion???

I poked around a bit at the website, but I didn't find an explanation of that parameter.

 

[caratgirl]

Hi Pqc,

Mine turned out odd like that too...the program re-calculated my crown angle, plus it gave me a bad girdle reading (it is really a true medium!). I don't think this program is too accurate, even though it gave me very good's on everything else. It is just strange.

 

[optimized]

That is an interesting tool, and I would be interested in knowing if it indeed is at odds with Garry's intellectual property. The similarities in concept are striking. Keep us posted on that, eh Garry?

For the record, I was pretty impressed with how well it extrapolated the other figures based on the input but (like others posting here) it seemed to miss the mark on the crown angle (it showed 33.4/33.6' vs. the Megascope 34.2'). On the other hand, it nailed the 40.8' pavilion angle, so at least some of the math looks reasonable. I suspect it has trouble with some of the calculations since it is only using the averaged crown/pavilion heights and doesn't ask for girdle/culet data.

In the end, my sweetie's stone got 'Very Good' across the board, with that mystery "Distortion" category showing a 'deep' rating. If the bar graphs are consistent though, a 'deep' rating seems to be a good thing. Wish they had some clarification on that point....

-Tim

 

[Mara]

They note that blue means 'very good'...so I guess the mysterious 'deep' means an okay thing. Not sure.

It calculated my crown angle pretty well, my little shallow crown angle. Girdle could be more of a subjective thing..though I guess one could argue that grading cut itself is a subjective thing anyway--as one's opinion through research may not always align with another view (e.g. GIA vs AGS on certain schools of thought).

All in all I think it's a great tool to add to the HCA, Bscope, IS and other tools we have online for fun. Without knowing more about it and the creator, can't really judge it all that well, but I was impressed at what it came up with for my stone (except for brilliance!).

 

[fire&ice]

Cool Tool Mara!

Mine came up VG in every catagory also. Mine also came up Shallow. My quess is that stones are either shallow or deep & the bar indicates how far off in either direction.

Curious, did any one get excellent & what criteria is excellent? What consitutes "good".

Also, I don't know what drives the boat. In HCA, I can adjust table size by .8 & get a much better score. I tried adjusting other parameters & the results were pretty much the same. The pavillion angle, mm's & table being the only constant.

 

[Mara]

Maybe they only have very good, good and poor. Anyone see an excellent? In the notes at the bottom it says something about blue text meaning a well cut stone, so that led me to believe that VG was the top of the scale. Esp if Tim's stone and other excellently cut stones are getting VG's only.

Though I just saw that it says a mathematically perfect stone will fill the bars to the end with blue. So I guess the more blue in your bars as opposed to red, the better.

 

[Mara]

Actually, I just realized I had my pav angle input into the area where the pav % should go. Woops.

So when I put in the correct info, I got this. Better!! Brilliance is much higher. The girdle seems to be a little off though, my girdle is more thin-med rather than med-slightly thick which is what it looks like the % it is giving me is. The one red marker is the crown/pav ratio, which is as it should be I guess as my stone is very shallow up top. Crown % is only 11.1 as opposed to the 13-15% you see in more typical 'ideal' stones.

 

[Final Cut]

Hey all,

Mara - this was very interesting ... I attach the results for my stone... The crown angle seems 0.3off (sb 34.1) but maybe because of a 0.8 culet...

Nice tool though - looks like Cut Nut will need to get an HTML programmer soon !! Looks matter ! .. lol

FC

 

[Mara]

FC--looks like your Distortion is the only 'Very Good' we have seen so far. Very interesting!!!

 

[slmulkey]

My diamond came up with all "very good" ratings except for distortion which was listed as "deep"...I wonder what that friggin means? It's strange that they ask for color and clarity and then don't tell you anything about that...what's the point. Also the color only goes down to "H" and the clarity only to "SI2"...perhaps they don't sell below that color and clarity. It's an interesting tool, see below for the explanation that I copied from their website. Has anyone heard of the Euliz cut?

http://www.jewellerycatalogue.co.uk/diamonds/round-brilliant.htm (click on diamond help in the right hand corner)

It can be seen therefore that a ratio can be realised for any given brilliant cut diamond, and which when calculated, will yield its deviation from the 100% brilliance of the Eulitz Cut (mathematically perfect). We can calculate this for you when you purchase a diamond from us and it indicates mathematically how well your diamond has been cut. We generally reject stones that fall below 9% deviation. You might think this is a hard line approach, but we aim to supply you with diamonds that exceed your expectations.



Types of Brilliant cut:

The 'Ideal' round brilliant cut has changed through out history, but in 1972 Euliz calculated the proportions necessary for 100% brilliance in a diamond. We are currently translating the work from German and will provide more information on the solution in the near future.




(Edited to delete chart that didn't show up when I pasted it...just visit the link above)

 

[pqcollectibles]

I totally disagree, Final Cut. While all the bars on the UK cut thingy are nice to look at, my diamond rates better on the HCA, so the HCA is better! LOL

Honestly, I really do like the info of the HCA better. While all the blue bars are nice to look at, the UK model is lacking. The UK model just measures cut and Distortion, whatever the heck that is. You get no idea from the UK model of what to expect in the way of visual performance for Fire, White Light Return, or Scintillation. Plus the HCA makes buying recommendations, warnings about steep angles, etc. What good are pretty bars if they don't "tell" you anything more than you can learn on your own with a little research, crunching numbers, and looking at charts.

Just my $0.02 worth

 

[mdx]

Interesting thread.

Anyone thought of inviting the UK site owner to join the discussion and tell us about his theories if any.

Wayne

 

[optimized]

"Anyone thought of inviting the UK site owner to join the discussion and tell us about his theories if any."

Already done. I sent a message to them a little while ago. I'm hoping someone from the organization will take the time to check the thread out and contribute.

-Tim

 

[jamesm]

Hi from the UK,

Tim, sorry for the delayed reply but I didn’t open my mail until Monday and Mondays are very busy.
Our diamond cut analyser (DCA) is no big deal, I have been using this kind of tool for around 20 years, as do other members of the trade in the UK. My first version was written by myself in BASIC and it progressed across lap tops, palms and finally made it to the internet for our UK customers. This is actually a cut down version of one that we currently use, written in PHP, with database facilities, price analysis and interrogation. I started to convert the DCA to javascript for the JewelleryCatalogue.co.uk site and then mid way through thought it would be nice to add a vector diagram of the diamond, which changed with the parameters entered. Thus it partly stayed in PHP. It only took a few hours to write so it probably requires a little fine tuning. If you are in the UK and there are any new features you would like then let us know. I started writing a 3D version during the Christmas holidays but got carried away with thoughts of laser mapping. It will have to wait.

I am surprised that we are being challenged on intellectual copyright, its very basic stuff and any credit should go the mathematician Eulitz, who calculated the ideal proportions for a brilliant cut diamond in the early 70's. Anyone with basic programming skills can write their own cut analyser, everything you need can be found in diamond grading handbooks, or on many of the excellent grading courses around the world.
However we have received an email from Gary Holloway warning of possible copyright infringement, and as much as I would like to contribute to the forum, until we receive the specific details from his Lawyers it would be prudent not to enter into any discussions.

Anything that brings awareness to the much neglected diamond cut has to be a good thing and its not rocket science. I am a Physicist, passionate about diamonds, not an International lawyer so we will just have to wait and see.!

Hope this is of interest, grateful for any feedback.

Regards

James

NB Can anyone point me to the GIA’s ‘brilliance’ report from 1998?
My personal email is [email protected]

 

[fire&ice]

Thanks James!


Are the blue bars *after* the recut or is that the diamond as is?

 

[Serg]

Hi James,

Thanks for your input.
Could you give internet link to Eulitz works?

 

[Mara]

James, kudos for coming up with such a cool program. I am sure that Garry feels strongly about his baby, the HCA, but I think it's great that customers have a tool such as yours to use in conjunction with something like the HCA for online diamond buying. Very helpful to have all views. I hope that you two can work things out amiably and you can go on updating the program! Laser mapping?! Ooh.

Also you note that the idea behind the program is really based on the Eulitz 70's idea of a brilliant round cut. How has that changed in the last 30 years and has your program been updated with any of the newer findings on cut? It's a hot topic from what we have heard, and I'd be curious to know what (if anything) has changed from the original Eulitz findings in respect to your program.

As F&I noted, we all have a few questions on the program since having found it. A few are listed below..would appreciate a post if you have the time.

1--What is distortion and what are the parameters for judging? Many excellently cut stones from forum members got 'deep' and 'shallow' with only one 'very good'.
2--What does the 're-cut' # mean, is that what the stone ctw would be if it was recut to the crown and pavilion angle that are noted in 'blue' next to the real crown and pavilion angles?

Thanks!

 

[mdx]

Hi Sergey

The work is titled “Die recherische Ermittlung der optimalen Brillanz des Brillanten” WR Eulitz (1972)

I think you can get a copy through Proffesor Verena Pagel Theisen of the Gubelin lab in Switerland

Hope this helps

Wayne
Melbourne Diamond Exchange Ltd

 

[mdx]

Hi Mara

Eulitz suggests an Ideal Cut with the following proportions with some deviation

Crown Height =14.45%
Girdle =1.5%
Pav Depth = 43.15
Table 56.5%
Crown Angle = 33.36
Pav Angle = 40.48
Ratio of crown height to pav depth 1:3,00

Wayne
Melbourne Diamond Exchange Ltd

 

[Talonnav]

Here's another "deep" w/VG.

 

[caratgirl]

Well, I figured out what happened to mine! It was user error

, seems I used pav degrees instead of % . Now my girdle is very good also, but I ended up with distortion deep too! What does that mean, I wonder?

 

[jamesm]

Hello again,

We have not received anything from Garrys Lawyers yet so I do not wish to encourage the use of our DCA. We currently have no financial interest in the USA so I hope this will be resolved quickly.
Garry, please will you email us the details from your Lawyers to expedite the process.

I have had a look for our copy of Die recherische Ermittlung der optimalen Brillanz des Brillanten to forward but it I think it has been lost over the years. If anyone has one or intends to write to Professor Pagel-Theisen please could we have another copy. (And if you don’t already own one order a copy of her excellent book Diamond Grading ABC ISBN 3-9800434-0-1 )

Thanks Wayne for the values. I think as you correctly say VPT quotes the ratio of Crownavilion as 1: 3.00, I think it actually calculates as 1:2.986. I only mention this because the figure is quoted to 2dp.
Crown angle is 33.6 degrees (decimal) or 36 minutes
Pavilion 40.8 degrees (decimal) or 48 minutes

This forum is an excellent idea, we don’t have anything like it in the UK that I am aware of. Excellent site too, lots of info. Even if we have a lawsuit, I will still read all this stuff, there is so much information and so many excellent contributions.

Regards

James
Still looking for a copy of the GIA’s brilliance’ report from 1998 – Garry you must have one!

 

[Garry H (Cut Nut)]

Hi James,
My patent has not yet been granted, but it is a requirement that a patent owner or pending owner takes the earliest opportunity to warn of any potential conflict.
I do not know that anything you are doing would cause a conflict, but it was my responsability to warn you

I have a hard copy of the brilliance article but I think GIA do not give permission for full photocoying. You should try a library - Gems & Gemology Fall 1998. I have known of Eulitz study for many years.

You are correct about the angles James.
This stone scores DiamCalc2 results of
Light return .98 and .99
Leakage .95 and 1.0
Contrast 1.0
HCA is 0.6

 

[oldminer]

Cut: Round
Weight: 1.13 carats
Table % 56 Grade: 1A
Crown Angle 33.75 Grade: 2A
Crown Height % 14.7 Grade: 1A
Pavilion Depth % 43 Grade: 1A
Girdle Thickness Medium to Medium Grade: 1A
Total Depth % 60.8 Grade: 1A
Polish / Symmetry Excellent Grade: 1A * Not a primary determining factor.

Final Grade: 1A


This is how the 1.13ct diamond above works in the AGA Cut Class calculator..... I think we are pretty much on the same wavelength.... I like the bar graph concept.

It is good to see a coming together of ideas once in a while.

 

[pqcollectibles]

Update on the guys from across the big pond.

I emailed/PM'd James to ask about "Distortion" and here is his reply to me:

------------------------"Quote"---------------------------

We are maintaining a low profile until Mr Holloway provides details of his copyright claim, and I am advised not to enter into discussion until we have seen this.

It’s a real shame, but if everything turns out OK I will be pleased to give regular input.

I think I can ask you what you like and dislike about the DCA and what you would like to see added?

Any feedback would be appreciated.

I can start by saying dislike: lack of notes on features!

I will sort that out at the weekend hopefully.

Thanks for the email,

Regards
James


-----------------------End Quote--------------------------

Looks like we may have to wait until the whole legal issue gets sorted out before we will know what "Distortion" is.

Or, James may post details on the Net sooner. Not really sure.