Over the course of time the term "brilliance" has come to be replaced with "brightness". Part of this is because of the breakdown into the individual metrics of brightness, dispersion/fire, scintillation, contrast, leakage etc. "Brilliance" is a word that takes on different meaning depending on who you're talking to. In the most general sense it is and has been used to describe overall diamond appearance, no matter what lighting conditions you brought the stone into. For example if you bring a highly dispersive stone into strong light conditions, like direct sunlight, this environment emphasizes the metric of fire/dispersion and if one were to say ... "wow, what a brilliant stone" or "that diamond has great brilliance"; although we would be observing the metric of fire/dispersion in direct sunlight all would understand the meaning implied by the use of the word "brilliant" or "brilliance".
GIA Definition of Brightness
AGS Definition of Brightness
Brightness and its relation to contrast as defined by AGS research gemologist, Jim Caudill states...
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What is Brightness?
The amount of white light returned to the observer.
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What is Brilliance?
Brightness with positive contrast effects.
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What is Contrast?
The light and dark patterns seen when observing a faceted diamond. It can be positive or negative in its optical effect. Usually caused by, but not limited to, the observer’s head.
When discussing the metric of brightness and the ASET, AGS states:
We'll come back to ASET in a moment and tie this all together.
When we left off in contrast we were comparing this table. This table will now come in handy because we will use it to demonstrate how contrast impacts brightness.
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Example of a flat white placard with No Contrast (Holloway) 100% light return.
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Bright Contrast (Holloway, Rhino)
50% light return/high intensity
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Low Contrast (Rhino)
50% light return/low intensity
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A recurring theme seems to pop up in each of the definitions.
The amount of white light returned to the observer. GIA and AGS are in agreement with regards to this metric.
Brightness Because of Contrast:
Referring back to our checkerboards, these 3 examples can represent diamond appearance with regards to this metric of brightness.
In the previous chapter on contrast we featured a diamond demonstrating the positive affects of contrast as defined by AGS. The lighting condition was low ambient hemisphere lighting. I get this view while standing in our store in one of the weakest lighting environments and demonstrates AGS' metric vividly to our clients. The arrows primarily reflecting back head obstruction while the rest of the facets reflecting back light from the hemisphere.
Now here is that same diamond alongside itself with one exception. The lighting conditions are a little brighter. This would be akin to taking the diamond away from weak ambient hemisphere lighting and into bright ambient hemisphere conditions ... say cloudy day conditions where the sunlight is being diffused through the clouds.
Note how contrast is increased and the diamond is brighter due to more intense reflections of light. Same diamond, different lighting conditions.
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low ambient hemisphere lighting
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bright ambient hemisphere lighting
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What do we learn from this? Very simple. A diamond can have excellent brightness because of contrast but at the same time that brightness can be increased depending on the light conditions you bring the stone into. You may be wondering ... where does the other board come into play? The flat white board alongside the other 2 checkerboards?
Brightness at the Expense of Contrast
While all diamonds exhibit contrast to some degree (due to leakage or obstruction) there are some that are very bright stones which have different contrast patterns and take on a different appearance.
Take this stone on the left for example, a former AGS "0" ideal. We have learned that blue in the ASET demonstrates contrast due to obstruction. Observe the ASET results of this former AGS Ideal. What's different? Here's the ASET of the diamond we've been using all along (on the right).
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Former AGS Ideal
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New AGS Ideal
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less blues = low contrast
lots of red = high brightness
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excellent distribution of blue = high contrast
lots of red = high brightness
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The diamond on the left is a stone which properly defines what I would consider "brightness at the expense of contrast". Let's see how this plays out in our bright hemisphere lighting conditions.
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Brightness at the expense of Contrast
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Brightness because of contrast
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Lower brightness due to lighting
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Static image
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Dynamic image
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Checkerboard
correlation
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Now we have correlated diamonds with the demonstrations of the checkerboards and you have learned how to positively identify both metrics of brightness and contrast within diamonds and also through ASET (proper amount and distribution of reds and blues). Now ... if you're thinking to yourself as you look at these rotating diamonds, "Hey ... I kinda like the diamond in the first example over the others with greater contrast", guess what?!? YOU are the buyer and while AGS may deem one as being ideal and the other a non-ideal, you are the one who votes because it is your money. Which diamond is more appealing to you? Only you can answer that. We encourage, at every opportunity to view the diamonds you are going to consider.
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