Difference between ideal cut and vendor superior cut?

[bruceb916]

What is the difference between a GIA ideal cut and a vendor''s superior cut for RB''s? ie BN''s Signature Ideal cut. Is it worth the extra money?

 

[Garry H (Cut Nut)]

GIA do not call diamonds "ideal" they use excellent as their top grade (which might not be all that excellent).

BN are opaque about their grading system. they will not for example take ideal-scope or ASET photo''s, which I think is a shame.

They use a lab called GCAL for some of their signature stone grades, and we are still waiting for Angelo Palmeri (sp?) who has joined this board to explain how their cut grading systems work. I am glad they try - but not happy we have no real info.

 

[stone-cold11]

For a GIA grading probably, GIA giving more lee-way compared to AGS in their definition of ideal, as you can see in a HCA grading plot. I do not think there is anything different in BN signature ideal, just that they regrade it to their more narrow grading system and send it to another grading company for grading. They will have more pictures, I think also a ASET and Brilliance plot on their signature report.

So the extra $$ is more for the extra grading done, you probably get a better diamond compared to their other stocks or at least more mind clean but probably can get a better deal with other vendors on PS if you search for it using the cut quality tool above. BN also has a larger stock to choose from, so you are more likely to find a stone within certain specs that other vendors but of course not their signature stones.

My 2cts opinion. :p

 

[stone-cold11]

Gary, don''t the GCAL report has some sort of plot that looks like a ASET?

 

[Garry H (Cut Nut)]

Date: 9/16/2008 4:45:50 AM
Author: Stone-cold11
Gary, don''t the GCAL report has some sort of plot that looks like a ASET?

Looks like, but is not like.

I would like a clear definition. but have not got it yet

 

[Finally!]

So what does the "white" image with the bits of blue and green around it show the prospective buyer? GCAL is calling it "optical brilliance". I was assuming that it was an actual picture of stone that shows the light leakage points, and, going by the key they provide, I could look at the picture and determine if it looked like the "excellent" pic in the key, or something less. I have to trust them that there is no better "look" for this measure than the "excellent" pic in the key. Now that I think about it, I'm going on faith here - I have no idea if a diamond with extremely little light leakage (all in the right places) would produce an image like this, or if it would look some other way. In fact, I don't know HOW the whitish image was produced at all.

What does the image with the red, blue, and black show the prospective buyer? They are calling it "optical symmetry". I was assuming this picture (of the stone, I assume) allowed me to make a determination of the stone's symmetry, based on a comparison with the key. I thought it was something like the ACET scope (which I have looked through at a jeweler's.) The image for "excellent" looks a lot like what a well-cut diamond looks like when viewed with an ACET scope, to my uneducated eye, but the colors are different. I see what looks to me like compass points - I assume these are the arrows. My assumption was, the more well-defined the compass points, the better the cut. At least in this instance I have my own experience to help me feel like I understand what I'm looking at, unlike with the "optical brilliance" image.

The thing is, there are no GCAL reports for mediocre-cut diamonds for me to compare the pictures with, for either image. Without them, I can't feel confident that the images - and what they imply - are genuine or just more marketing.

It's funny - when I started this post I was a fan of the GCAL report. I like its layout, and I thought I understood what I was looking at. But now... I'd like to see the explanation of GCAL's grading, too.

 

[GCAL]

Guys,

Thank you for the inquiry and for the opportunity to better expalin GCAL''s Cut Grade and the Direct Assesment Light Performance (Optical Brilliance & Optical Symmetry) we utilize on just about every diamond GCAL certifies.

LIGHT PERFORMANCE
The light returned through the crown of the diamond is analyzed by GCAL in two categories: optical brilliance and optical symmetry.

The methods analyze the actual diamond and not a model, which means every nuance, such as inclusions and transparency, are considered.

OPTICAL BRILLIANCE ANALYSIS
The Optical Brilliance image is actually a digital photograph of the diamond taken in a special lighting environment that creates a strong contrast between the bright and dark areas. The image is then processed in a proprietary computer program that calculates the percentage of brilliance and the amount of light loss. This is a scientifically accurate and repeatable way to measure brilliance. The light gray areas of the image are facet outlines resulting from image processing to provide a realistic representation of the diamond’s unique faceting.

In the Optical Brilliance Analysis image on the certificate, the white represents the light return and the blue represents areas of light loss. The light return is quantified based on measurable light return (aka – performance) and then graded as: Excellent, Very Good, Good, Fair or Poor.

Since the Optical Brilliance is measured by direct assessment, meaning that it is judged based on the way each diamond actually performs rather than a theoretical model, the brilliance image of each individual diamond will always look slightly different.

Example of Excellent Optical Brilliance http://www.gemfacts.com/certs/br/181770141br.jpg
Example of Good Optical Brilliance http://www.gemfacts.com/certs/br/172970075br.jpg

OPTICAL SYMMETRY ANALYSIS
Symmetry is the beauty and organization of everything in nature, science and art. Aesthetically pleasing proportions and balance represent perfection. Patterns repeated in radial or reflective symmetry have harmony. The symmetry of a diamond’s facets is in fact artwork created by the master craftsman who cut the diamond.
The Optical Symmetry Analysis image is a digital photograph taken of each diamond in a special lighting environment that reveals the patterns of light return. All light returned at the same angles is represented by the same color. For example, all red areas represent light being returned within a consistent angle range. Therefore, the Optical Symmetry assesses the consistency of angles and alignment of facets by looking at the equality of light return. The symmetry of the color pattern demonstrates the balance, angle equality and alignment of each facet.

Since the Optical Symmetry is measured by direct assessment, meaning that it is judged based on the way each diamond actually performs rather than a theoretical model, the symmetry images of each individual diamond will always look slightly different. Like the beauty and ever changing color patterns in a kaleidoscope, each diamond reveals its unique reflective pattern of symmetry.

Example of Excellent Optical Symmetry http://www.gemfacts.com/certs/y/181770152y.jpg
Example of Fair Optical Symmetry http://www.gemfacts.com/certs/y/181960054y.jpg
CUT GRADE
The GCAL Cut Grade encompasses ten factors to determine a diamond’s light handling ability. These factors are separated into the categories of Light Performance, Finish and Proportions. The sum of these categories equals the total Cut Grade, with Ideal (100) being the highest possible grade. I have attached our cut grade integration chart that shows how each Cut Grade can be attained.

CUT GRADE - LIGHT PERFORMANCE
GCAL utilizes Diamond Profile® direct assessment imaging technology to visually illustrate and analyze a diamond’s Optical Brilliance and Optical Symmetry. Light Performance is the most significant attribute of the total cut grade.
Points awarded in this category are: Excellent (40), Very Good (35), Good (30), Fair (25) and Poor (20).

CUT GRADE – FINISH
Finish is comprised of two grading factors: Polish and External Symmetry. Finish is graded by examining a diamond’s surface under 10x magnification.
Points awarded in this category are: Excellent (30), Very Good (25), Good (20), Fair (15) and Poor (10)

CUT GRADE - PROPORTIONS
Proportions are calculated by a computerized measurement technology, which produces an individual diagram with the actual dimensions and angles of each diamond. The GCAL Cut Grade considers six proportion factors: table%, total depth%, crown angle, pavilion angle, girdle thickness and culet size.
The total points awarded in this category are: Ideal (30), Excellent (30), Very Good (25), Good (20), Fair (15) and Poor (10)

That''s a quick summary of GCAL''s light performance and Cut Grade methodologies. Please feel free with any follow-up questions...we would be happy to answer any of your questions.

Thanks

 

[stone-cold11]

A question on the GCAL report. Why is it that some reports do not have the optical brillianace analysis and optical synnetry analysis printed on the report?

 

[VVFF]

Date: 9/17/2008 10:57:27 AM
Author: Stone-cold11
A question on the GCAL report. Why is it that some reports do not have the optical brillianace analysis and optical synnetry analysis printed on the report?

Those are probably princess or other fancy cuts that they don''t do the brilliance assessment on.

So that leads me to my follow up question. Are the fancy shape''s "cut" simply graded on table and depth/crown percentages combined with their finish grades?

 

[Kelli]

Just wanted to chime in and agree that not all GIA excellents are excellent. I made the mistake of thinking they were, and will probably not buy a GIA stone ever again, now knowing there are far more reliable grading reports.

 

[Paul-Antwerp]

So, the ''Optical Brilliance Analysis'' is an idealscope without a viewer and with different colour-coding.

And the ''Optical Symmetry Analysis'' is a funky way of showing the symmetry of a diamond, in which I do not understand whay the meaning is of ''light returned at the same angles''.

Is this the summary?

 

[GCAL]

Just about every GCAL certificate has Optical Brilliance Analysis...Optical Symmetry is included on many but not all.

 

[GCAL]

Date: 9/17/2008 11:02:33 AM
Author: VVFF

Date: 9/17/2008 10:57:27 AM
Author: Stone-cold11
A question on the GCAL report. Why is it that some reports do not have the optical brillianace analysis and optical synnetry analysis printed on the report?

Those are probably princess or other fancy cuts that they don''t do the brilliance assessment on.

So that leads me to my follow up question. Are the fancy shape''s ''cut'' simply graded on table and depth/crown percentages combined with their finish grades?

In order for a fancy shape to get a cut grade, optical brilliance & symmetry must be included. A fancy shape''s cut is graded the same way as round brilliants, just with different proportions

 

[stone-cold11]

So why aren't these analysis pics included in the report of for example a princess cut if the pics are already taken for analysis? I would have thought that would be more useful for the buyer than all those words and diagrams of the cut as printed? Fancy cuts relies more on viewing optical performance report to determine a good cut than round brilliant, I would have thought it would be common sense to include that?

 

[GCAL]

Date: 9/17/2008 11:30:56 AM
Author: Stone-cold11
So why aren''t these analysis pics included in the report of for example a princess cut if the pics are already taken for analysis? I would have thought that would be more useful for the buyer than all those words and diagrams of the cut as printed? Fancy cuts relies more on viewing optical performance report to determine a good cut than round brilliant, I would have thought it would be common sense to include that?

GCAL includes the optical brilliance image and analysis on just about every diamond we certify, and on every diamond that we certify for Blue Nile. Optical Brilliance measures light return, which we believe is an essential element for a consumer to make an informed decision.

GCAL offers an extensive variety of images and analysis that not all clients choose to display on the certificate. For example, GCAL gemprints every diamond we certify, some reatilers choose not to have that reference, image, or information displayed on the certifcates we produce for them.

We do not, and cannot force clients to take advantage of the entire menu of services we offer. As it is, the GCAL certificate, even in an abbreviated format, provides much more consumer informative and consumer friendly information than any other lab report.

That brings me to my conclusion, that GCAL is the only laboratory in the world, that has a fully backed guaranteed certificate for the accuracy of the 4 C''s...further, GCAL is one of only three labs in the world that has been laboratory certified and accredited ISO 17025.

 

[stone-cold11]

So what you are saying is the Blue Nile choose not to display the pics of the Optical brilliance and symmetry pictures on the certificate you issued? Is there anyway we can view the associated Optical pictures of the reports on GCAL site? Or is that limited access because Blue Nile choose not to include those pics in the report? Do they need to pay extra for those information to be presented?

I am just wondering how best to assess information available about GCAL certs to determine if a particular fancy cut is of my liking instead of just assuming a GCAL certified diamond is to my liking and that individual stones do not have their distinctive character. Not dissing GCAL or anything.

 

[GCAL]

Date: 9/17/2008 12:04:37 PM
Author: Stone-cold11
So what you are saying is the Blue Nile choose not to display the pics of the Optical brilliance and symmetry pictures on the certificate you issued? Is there anyway we can view the associated Optical pictures on GCAL site?

That is not what I am saying...take a look at the GCAL certificates on Blue Nile...you will see that is not the case.

 

[stone-cold11]

Ok, look at this report number than. 172550020

This is the one I bought so I am sure the optical plots are not included in the report. I check the report check on your website to make sure I got every part of the report and yes, it is the same as what I have.

 

[strmrdr]

strong iso(white dome) no head with purple background then do a post process color match to remove the border and then apply a red outline which I didn't bother doing.

edit: woops meant to quote Paul...Hope this helps understand what is going on with the images.

 

[strmrdr]

The post process color match is why you get the dips in the outline as seen here.
The color was a very close match to the background so it got removed.

 

[VVFF]

http://www.bluenile.com/certs/619/GCAL181900005_zoom.jpeghttp://www.bluenile.com/princess-cu...=expReport&cert_icon=gcal_zoom#grading_report

I bought this diamond and as you can see it is rated "Blue Nile Signature Ideal" in cut but shows no images of the optical analysis. So how was the cut judged?

 

[VVFF]

Bumping this because I am still wondering why there are no optical images when you say there should be.

 

[GCAL]

Date: 9/18/2008 1:25:29 PM
Author: VVFF
Bumping this because I am still wondering why there are no optical images when you say there should be.

I apologize about that...i was mistaken. The rounds have both images and the fancies have neither.

 

[stone-cold11]

And why is that so if the data is already there? Why not post it on the report?

 

[VVFF]

So my question is still this; Are the fancy shapes judged at all on light return or simply of table/depth percentages and finish details?

 

[Garry H (Cut Nut)]

Date: 9/17/2008 12:16:18 PM
Author: strmrdr
strong iso(white dome) no head with purple background then do a post process color match to remove the border and then apply a red outline which I didn''t bother doing.

edit: woops meant to quote Paul...Hope this helps understand what is going on with the images.

Dear Angelo (sorry for misspelling your name earlier) thanks for popping in for explanations.

I have lots of questions - but we will not try to do too much too quickly.

Re the image Storm has been discussing - the one that purports to display Optical Brilliance.
This image is of a stone with very little leakage, using your methodology your image should be very similar to this one (I could be wrong of course).
If I am correct - the stone is an absolute dog - it would have only around 2/3rds of the light return of a nice round and it would have very ugly appearance to boot.
Care to comment?

 

[strmrdr]

Date: 9/19/2008 2:23:54 AM
Author: Garry H (Cut Nut)

Date: 9/17/2008 12:16:18 PM

Author: strmrdr

strong iso(white dome) no head with purple background then do a post process color match to remove the border and then apply a red outline which I didn''t bother doing.


edit: woops meant to quote Paul...Hope this helps understand what is going on with the images.

Dear Angelo (sorry for misspelling your name earlier) thanks for popping in for explanations.


I have lots of questions - but we will not try to do too much too quickly.


Re the image Storm has been discussing - the one that purports to display Optical Brilliance.

This image is of a stone with very little leakage, using your methodology your image should be very similar to this one (I could be wrong of course).

If I am correct - the stone is an absolute dog - it would have only around 2/3rds of the light return of a nice round and it would have very ugly appearance to boot.

Care to comment?

I''m interested in the answer also.
But thinking out loud it would be easy enough to to run an average on the pixels in the stones image and separate that one out. (Imagem does this)
I suspect that the images are done in b&w and the color added latter to the gcal pictures but will stand corrected if told otherwise.
They are obviously heavily edited before being put on the report.

 

[Garry H (Cut Nut)]

It is possible Karl

Here is an ASET of the stone I posted above

 

[stone-cold11]

Date: 9/18/2008 1:34:40 PM
Author: Stone-cold11
And why is that so if the data is already there? Why not post it on the report?

Bumping this thread in the hope that Angelo see this and answer to our concerns.

 

[Finally!]

OK, I have to admit that Karl and Gary have lost me.

Can someone summarize the concern? Thanks.