Contrast Brilliance/Scintillation and the Isee2 Technology

This is a portion of a new tutorial regarding my most recent research into the issues of contrast brilliance/scintillation and the Isee2 technology.  While hot topics are being posted on the issue of cut I couldn't think of a more appropriate time to post this article and I wanted my friends on PriceScope to be able to read it first.

 

Leonid, please feel free to edit/change/add out portions you deem inappropriate.

 

Contrast Brilliance & Scintillation and a more indepth look at the Isee2 Technology.

 

The Isee2 technology measures 3 elements regarding cut quality and the diamonds beauty.  Those three elements are brilliance, scintillation & symmetry. Before I begin to introduce you to the analysis this technology performs it is important to introduce you to some new concepts concerning brilliance, scintillation & symmetry that you may or may not be familiar with.

I am going to ask that you remove from your mind anything you've learned about diamond brilliance for a moment and walk with me as we think outside the box for a moment. 

Contrast Brilliance & Scintillation

Brilliance:

There is an element to brilliance within diamonds that relates to the contrast seen between facets reflecting back light vs facets reflecting back other elements that are blocking light (ie. your head or body blocking light from behind which the diamond is reflecting within).  To demonstrate this point of contrast I'd like to use a few examples to illustrate.

This first example illustrates 2 checker board patterns.  The board on the left has an extreme degree of contrast (black and white squares)
while the board on the right is the same exact graphic except with reduced contrast, thus changing the colors to different shades of gray.

Sit back from your computer for a moment and gaze at your screen.  One of these checker boards is brighter, more brilliant and attracts the
eye more than the other.  You are now beginning to grasp the concept of contrast brilliance. 
 

Another example I can point to is the contrast setting on your television set.  When you increase the contrast your picture becomes brighter and more brilliant.
The graphics above are also depicting this aspect of brilliance as well but you don't see the pixels blown up to this level on your television set.  However if you were to look at it on a blown up pixel by pixel basis you'd observe the element we are demonstrating above.

This is important in diamond beauty and brilliance because when diamonds are observed in diffuse/office light conditions the laymen is observing one of 3 phenomena.

• Facets reflecting back white light. 
• Facets reflecting back objects blocking the light (like the shadow of your head/body blocking light).
• Light leakage (which would reduce contrast).

It is important to understand that diamonds take on a completely different appearance in diffuse/ambient/office light conditions than they do in stronger direct light conditions.   Strong direct light conditions emphasize fire (or colored light return) and scintillation within a diamond and is dependant upon the strength and intensity of the light return through the crown of the diamond as depicted in this graphic.  We perform optical analysis which represent diamond beauty in these light conditions but this is NOT what the Isee2 is analyzing as it's analysis is done in diffuse light conditions.

Take the same super ideal diamond away from the strong lights (like sunlight, halogens, etc.) and into softer light conditions (office/diffuse/ambient) and now you would be primarily observing the contrast between white light return and areas reflecting back things that are blocking the light.  This graphic taken in office light conditions demonstrates the point.  Next to it is a diamond with poor contrast brilliance/scintillation.  There is a clear observable distinction between these 2 diamonds that the average laymen can easily distinguish.

 

Differing views

Indeed this tutorial is not the first article written on the subject of contrast brilliance, it is however a slightly different concept from that offered by others within the gemological field.  Reference is made to it by our friends at Moscow State University (reflected in the DiamCalc software as well) and from Peter Yantzer (CEO of AGS Laboratories) view contrast brilliance slightly different although we are all primarily on the same frequency.  The contrast they depict is what is also being considered in this study but also that of light return vs light leakage, hence in the DiamCalc software a diamond is rewarded with a higher "contrast brilliance" score when more leakage exists.  This does not make sense to me since in my analysis and study of this subject; light leakage contributes to less contrast since there are less reflective surfaces off the pavilion facets, not greater contrast. The more leakage that exists the more dismal the diamond will appear under both diffuse and direct light conditions.  I would propose to my gemological friends that the most attractive and appealing contrast is not that of light return vs light leakage but that of pavilion facets reflecting back light vs pavilion facets reflecting back shadows of what is blocking light (ie. head obstruction, etc).  So the contrast is that of lights/darks only.  Light leakage detracts from this light/dark contrast since there are no reflections back to the viewer except what is seen underneath the diamond.  Large portions of light leakage contribute to the decrease of contrast brilliance, not enhance it.

Scintillation:

While contrast brilliance focuses on the depth of lights/darks reflected back from within the stone, contrast scintillation focuses on the amount of and points of contrast that exist within the stone.  Ie... Are we looking at a checkerboard pattern that consists of 24 squares or 100 squares?  The more points of contrast that exist within the diamond the more scintillating it will be in diffuse light conditions.

All of the subject diamonds we have tested for contrast scintillation have been those of 57-58 facet rounds brilliants.  There are rounds that have been introduced on the market with more facets than this.  I would be curious to test properly proportioned rounds with more facets than the standard to see if their scintillation scores are higher (ie. more squares on the checkerboard = more scintillation theory).  I would assume this to be the case but don't know until I test em.

          

These are the elements of brilliance & scintillation that the Isee2 Analysis is performing and correlates perfectly with human eye observation under those conditions.

The reason this is important to the consumer and ultimately the beauty of the diamond is because soft light conditions are perhaps the most common conditions which most people observe diamonds under.

My studies have also shown me that the intensity of light being reflected within the diamond is not as critical as it is in direct light conditions.

In direct light conditions the amount of fire and scintillation observed is dependant upon how much light is primarily being directed at high and medium angles (high angles are from 76° to 90° (observer head), medium angles are from 45° to 75° and low angles are from 0° to 44°)1.  We can observe this phenomenon in our LightScope technology which shows us plainly the blacks, and contrast between dark and pale reds.  Blacks and dark reds representing the high and medium angles.

In softer light conditions light being reflected at the lower angles (0° to 44° or light reds in LightScope) plays a more prominent role and doesn’t affect the reduction in light return as much in these conditions because in softer light conditions we are primarily observing moreso the element of reflective/non-reflective surfaces.

A diamond that demonstrates this point is this stone. 

You can plainly see the pale reds under the table which demonstrates areas within the diamond that reflect light weaker than other areas that are in dark red & black.  This affects to a degree it’s performance in direct light conditions which is reflected in it’s BrillianceScope results…

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however, although weak, they still are reflective surfaces on the pavilion and in softer light conditions contribute to the reflective properties of the diamond in those conditions.  The stone has excellent contrast and it’s surfaces are still acting as reflectors, couple that with it’s outstanding symmetry and you can understand why it gets an Isee2 score of 9.8

The point is all reflective surfaces within the diamond, both weak and strong, contribute to the contrast brilliance/scintillation within the diamond.  Blatant leakage (whites in LightScope) contribute to it’s decrease in contrast.

Illuminating the Diamond's Checkerboard

Note how the facets on the diamond on the left all correspond perfectly with regards to their black/white illumination.  Every internal reflection is illuminated to the identical color of it's opposite corresponding reflection.  Where you see black on one side you see black on the other.  Where you see white on one side you see white on the other.  The depth of contrast is top of the line.  Not only the depth but the amount of blacks/whites is superior among those within round brilliants contributing to the very high scintillation score.  Lastly, this optical symmetry pattern is insanely consistent facet by facet, reflection by reflection.   The obvious difference is seen in the 2nd graphic and represents more common cut qualities on the market.

Symmetry:

Lastly the Isee2 Analysis grades symmetry.  The symmetry being analyzed however is not that which is traditionally thought of with regards to symmetry grading as done by the labs (GIA, AGS, etc.).  The symmetry being analyzed on the Isee2 is that of optical symmetry.  Facet alignment on a 3 dimensional, optical scale.  We already perform this type of analysis when we photograph our Hearts & Arrows diamonds.  The difference is this is taking this analysis into the digital realm and putting a technical eye to the subject of optical symmetry and grading it digitally.  Considering the 2 types of symmetry grading (lab graded 2 dimensional symmetry, vs optical/digital graded 3 dimensional symmetry) I can tell you with all confidence which of the 2 affects diamond beauty more and that is the 3d symmetry.

For more details on lab graded symmetry I refer you to this link. http://www.goodoldgold.com/symmetry.htm

Optical Symmetry:

Two ways we currently analyze optical symmetry is through the H&A viewer (called by various names) and through our own LightScope viewer. Each viewer shows us different aspects about the optical symmetry & design of the diamond. 

The example below depicts 2 diamonds that have a high degree of internal relflective/refractive properties (both have minimal leakage), however one is severely lacking in optical symmetry while the other is far superior.  One of these diamonds took approx. an hour to cut while the other took approx. 4 hours.  Both of these diamonds are valued quite differently as well and for good reason.  Certain cut grading tools on the market (the HCA & the BrillianceScope) do not take into account this aspect of craftsmanship which could mistakenly lead a person to believe that 2 stones are of equal beauty or value when the case can in fact be the exact opposite.

This is one of the most important features of the Isee2 technology.  It puts a technical eye to superior craftsmanship and rewards the diamond accordingly.

Here is the Isee2 Analysis on the 2 diamonds above.

Lastly, optical symmetry analysis would not be complete with a view to the pavilion side.  This is done through the H&A viewer which shows optical symmetry through both the crown & the pavilion.

Assigning a Numerical Cut Grade:

The Isee2 Analysis, after looking at the features of brilliance, scintillation & symmetry calculates a final numerical score ranging from 0.0 to 10.0.  However the device is designed not to give any diamond a score higher than 9.8.  Our experience has shown us that the most excellently cut diamonds range in their Isee2 scores from the high 8's to over 9's.  We generally limit our purchasing to diamonds with Isee2 scores over 9.

 

 

I've put together some FAQ's on this subject already based on questions I've received in the past.  Any good questions posed here I'd like to include so whatever questions ya'll have on the subject don't hesitate to ask.

 

Kind regards,

Rhino

Thanks Hodne,

 

The greatest challenge was being able to write/communicate in a way that the average laymen can understand.  I hope that I have kept it simple enough for the average laymen to grasp.

 

Thanks for the questions strmrdr.  My answers will be between your questions.

 

I hope this newsletter and the feb one would also help you understand the concept