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Question about performance rating as a function of color, clarity, carat, etc.

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Adylon

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Nov 14, 2006
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I'm hoping a diamond cut nut can answer my question :) I've always wondered this but wasn't sure if anyone was able to quantify it or have something to offer in terms of some real analysis.

So anyhow my question is: How does carat (or diameter), color and clarity affect a diamonds ability to reflect light performance-wise?

For example;

Does a 2ct reflect double the amount of light then a 1ct all things being equal? Or does a 7mm reflect 16.7% more then a 6mm? [{7-6/6)x100%=16.7%]

Does a SI2 lose say 20% of it's light refraction efficiency compared to a FL clarity because of it's flaws scattering the light internally? What about SI1, VS, VVS?

What about color? Does going up in the color scale also affect the efficiency of a diamond's ability in light performance?

The reason I'm asking is because I'm trying to quantify just how much "Performance Based Value" there is based on all the 4 C's and not just cut. We all know these things make some difference but just how much is the real question? Like is a 1.20ct VS2 AGS1 just as bright as say a 1.10ct SI1 AGS0 due to it's size and clarity advantage? Thanks in advance :)
 

kcoursolle

Super_Ideal_Rock
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Jan 21, 2006
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10,589
This is a good question that I cannot answer, but I have noticed that bigger diamonds tend to have broader flashes than smaller diamonds (assuming all are well-cut). Hopefully an expert will chime in about this, very interesting topic.

EDIT: I think for the most part as well, unless a stone is heavily included or filled with clouds an SI2 will sparkle about as much as a much higher clarity stone.
 

JulieN

Super_Ideal_Rock
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Jul 25, 2005
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13,324
size: what you see vs what you can't see

definitely not 20% for SI2; Paul said maybe 5% for Imperfect (or maybe said 5% of an I1/2 stone's face would be be included)

color effect would be measurable, but you can cut different proportions for different colors.

you forgot fluorescence.

marty is pretty into the fluorescence and color. garry or serg would probably hit the size one. and clarity....maybe Dave Atlas.

reading material about this exists on PS, but mostly dispersed and through several years, so it is hard to find.
 

shiatsu

Rough_Rock
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Jan 2, 2007
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Ya know everything I've seen is subjective, except for the Gemex reports. Even GIA's grading is based on what their study of how hundreds of people thought best looking diamonds were cut. Mathmatically the diamond's light would be a measure of it's reflective surfaces that reflect upwards, which would mean there's gotta be a point of diminishing returns. Generally if you double a diamond's carat weight the diameter will only get about 25%-30% larger. You have to increase a diamond's carat weight almost ten-fold before you see double the diameter. So the small diamonds have the largest surface area relative to it's size- probably why we see so much sparkle from pave.

carat weight - diameter
0.06 ct - 2.5 mm
0.10 ct - 3.0 mm
0.12 ct - 3.2 mm
0.25 ct - 4.0 mm
0.50 ct - 5 mm
0.75 ct - 6 mm
1.0 ct - 6.6 mm
1.25 ct - 7.0 mm

But then there's objectivity again to consider, a certain amount of reflective flash will blind the eye while slightly less flash may seem like a very weak flash to the eye. And each person may be slightly different here. The amount of color to white light in the flash may make a different impression as well, then the's that hard to quantify value of scintillation.

As far as color goes, it's mostly just a different color of light ad doesn't affect the amount of light returned much. But obviously the D-E-F colors look slightly better than the G-H-I-J colors. As far as clarity, ya know some SI clarity stones don't affect the light returned and some do. Anything VS and above probably should have negligable affect on returned light. I mean if you can't see it without a loupe how much will it really affect your light return?
 

strmrdr

Super_Ideal_Rock
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Nov 1, 2003
Messages
23,295
Interesting question,
You will get a lot of opinions but a definitive study hasnt been done...

My opinion from listening to others around here,,,
d-j - not enough to consider other factors make a bigger difference such as pavilion tolerences so its pretty small.
clarity - until you get to si clouds very little and again other factors are likely bigger.

The size issue comparing bling/price/size in todays market .97ct and under is where it is at in RBs in my opinion. (just under the 1ct jump).
The price per surface area jumps a large amount once you hit 1ct and goes up from there.
Considering that you can buy almost 4 1ct and 8 .75ct diamonds for the price of a 2 ct diamond of the same cut clarity and color. The 8 .75s are going to have a lot more bling.

2.004 G VS1 $30380
1.007 G VS1 $7781
0.75 G VS1 $3520

All ACA''s of similar make.
 

stebbo

Shiny_Rock
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Jun 8, 2006
Messages
466
Date: 1/29/2007 7:59:37 PM
Author:Adylon

Does a 2ct reflect double the amount of light then a 1ct all things being equal? Or does a 7mm reflect 16.7% more then a 6mm? [{7-6/6)x100%=16.7%]

Does a SI2 lose say 20% of it's light refraction efficiency compared to a FL clarity because of it's flaws scattering the light internally? What about SI1, VS, VVS?

What about color? Does going up in the color scale also affect the efficiency of a diamond's ability in light performance?
My understanding concerning the effects of siz, clarity and color on brightness:

Carat - the bigger the diamond, the more light it gathers from around but the bigger area it reflects over as well. So flashes will only be broader.

However, internal light absorption is higher (think of shining a torch through the edge of a pane of glass). A perceivable loss of brightness.

Light disperses (breaks into colors) more the further it travels through a bigger diamond, leading to lower white light return, yet more colored light return (fire).

Clarity - if we can't see the inclusions with our naked eye, there's even less chance we're going to see their effect on brilliance with our naked eye. The inclusions we can see with the naked eye, well they're still so tiny compared to volume of a diamond to be in the way. It's going to take a bad I clarity before a noticeable drop in light performance.

Color - Well a diamond with color is like a piece of yellow colored cellophane. White light passing through gets its blue component absorbed. This of course is a loss of energy, but with a diamond and its relatively insignificant tinting, the loss in brightness is again insignificant, especially as the eye responds to the brightness of yellow the most anyway (compared to the other wavelengths making up white light).


Like is a 1.20ct VS2 AGS1 just as bright as say a 1.10ct SI1 AGS0 due to it's size and clarity advantage? Thanks in advance :)
Impossible to answer, as an AGS1 could feasibly be brighter than an AGS0 given equal color, clarity and size, but I don't believe clarity, size and color can come close to making up for loss of brightness due to slightly poorer proportions.

Stebbo
 
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