WHY do people want whiter diamonds?

[Tourmaline]

The top six things affecting the look of any diamond are:
lighting
lighting
lighting
lighting
lighting
cut

Hahaha! I love it.

 

[Tourmaline]

One would think Tourmaline's diamond is drawing alot of low angle light in order to be reflecting the wall colors so dramatically. (Unless the ceiling is also painted the same color or photo is shot with hand perpendicular to the ceiling).
Very interesting collage.

No, the ceilings are white and the photo was taken with my hand parallel to the floor and ceiling. I was in my daughter's room and happened to look at my ring (which I do a million times a day, hee hee), and I saw that it looked totally pink! So I got my camera and took photos in a bunch of different rooms.

 

[Rhino]

Karl, Garry ... based on what we've gone over in this last topic, do you think these would be an accurate statements? If not how would you refine?

"The length of light rays in a diamond or the more it will refract within the diamond will cause color entrapment thus making a diamond face up to a stronger tonal color than how it may be graded in the face down position.

At the same time, while ideal cut diamonds appear whiter than their non ideal counterparts they will not necessary have color entrapment but will be perceived to be a lower color merely due to the fact that the ideal cut is reflecting back more bright white reflections than the non ideal. The areas of blatant leakage showing the color behind the diamond, while areas of secondary leakage showing a gray tonal colors.

Thoughts?

 

[GemFever]

no,
The top six things affecting the look of any diamond are:
lighting
lighting
lighting
lighting
lighting
cut

This looks like a great thread, can't wait to go through it after work. Love this quote though!

 

[Rhino]

Based on the studies of optical scientist Jose Sasian who worked with AGS to refine their ASET technology, the theory states that light entering from the 0-45 degree angular spectrum (green in ASET) is weak ... dull illumination as light bouncing off of walls is not bright nor as intense as light entering from the 45-75 degree angular spectrum (red in ASET). Hence dull in = dull out.

Rhino

AGS far underestimates the effect of low angle lighting.
Many people spend much of their day or should I say evening where low angle lighting is the brightest lighting.

One would think Tourmaline's diamond is drawing alot of low angle light in order to be reflecting the wall colors so dramatically. (Unless the ceiling is also painted the same color or photo is shot with hand perpendicular to the ceiling).
Very interesting collage.

I was thinking her diamond may produce considerable red in ASET but not the strength of blue we'd typically see in H&A' with 75-78% lower halves

 

[Karl_K]

Karl, Garry ... based on what we've gone over in this last topic, do you think these would be an accurate statements? If not how would you refine?

"The length of light rays in a diamond or the more it will refract within the diamond will cause color entrapment thus making a diamond face up to a stronger tonal color than how it may be graded in the face down position.

At the same time, while ideal cut diamonds appear whiter than their non ideal counterparts they will not necessary have color entrapment but will be perceived to be a lower color merely due to the fact that the ideal cut is reflecting back more bright white reflections than the non ideal. The areas of blatant leakage showing the color behind the diamond, while areas of secondary leakage showing a gray tonal colors.

Thoughts?

needs to be ungeeked and add That some cuts by design have have areas of minor leakage which can increase contrast in a positive way.
Or words to that effect.

 

[JulieN]

Based on the studies of optical scientist Jose Sasian who worked with AGS to refine their ASET technology, the theory states that light entering from the 0-45 degree angular spectrum (green in ASET) is weak ... dull illumination as light bouncing off of walls is not bright nor as intense as light entering from the 45-75 degree angular spectrum (red in ASET). Hence dull in = dull out.

Rhino

AGS far underestimates the effect of low angle lighting.
Many people spend much of their day or should I say evening where low angle lighting is the brightest lighting.
With the laws mandating cfl it is also very flat and soft light in many cases.
Perfect lighting for omc/oec or other cuts that take advantage of it(*cough* Octavia).
The omc and oec were designed for low level soft lighting that was prevalent in their day.

What combo of red/green is best for earrings?

 

[Karl_K]

I was thinking her diamond may produce considerable red in ASET

I would think so also.
What AGS is missing that areas of a diamond can be red in ASET and still draw light strongly from the green region in ASET.
I haven't worked out a total proof yet but know it happens and can be enhanced by the design.

Here is why AGS underestimates it, it plays little part in a modern tolk.
Here is an image with the red zone black.

compared to the full ASET

 

[Karl_K]

What combo of red/green is best for earrings?

If I was designing a design for earrings I would as much as possible draw light from the red/green border region making sure to have strong green region draw in the red areas.
Closest thing you might be able to find on the market in a round is a good fic or oec.

 

[Garry H (Cut Nut)]

Karl, Garry ... based on what we've gone over in this last topic, do you think these would be an accurate statements? If not how would you refine?


"The length of light rays in a diamond or the more it will refract within the diamond will cause color entrapment thus making a diamond face up to a stronger tonal color than how it may be graded in the face down position.
Jon inside the diamond the light is reflecting around, and sometimes small amounts 'refract out'. The internal reflections work like the difference between looking thru the side of a very tall glass of orange juice vs looking down from the top. When refraction happens (light is inside the critical angle of 24.5 degrees) there is a portion of the light escapes. Never all of the light can escape - at 90 degrees internal bounce 83% of the ray will exit but 17% will still reflect back inside the gem. If that happens then the ray could exit out the crown, and possibly in the direction of a light source, and so be brighter, or out the pavilion and be duller, darker, greyer or browner.

At the same time, while ideal cut diamonds appear whiter than their non ideal counterparts they will not necessary have color entrapment but will be perceived to be a lower color merely due to the fact that the ideal cut is reflecting back more bright white reflections than the non ideal. The areas of blatant leakage showing the color behind the diamond, while areas of secondary leakage showing a gray tonal colors.
I do not know what the definition of blatant and secondary leakage is Jon? All ideal cut diamonds leak. In the image you can see around 20% leakage in a default DC ideal cut.
Thoughts?

 

[Karl_K]

Same images for a very well cut fic. model.

Mod. ASET with the red zone black

regular ASET



This shows the difference.

Disclaimer: this is not a high level of proof yet because ASET does not show the intensity of the return.

 

[Karl_K]

In an earring the obstruction would be reduced and the blue zone smaller and less intense.
Garry, any opinion on what degree of obstruction to use in simulating earrings?

 

[Demon]

Aww, thanks Yssie.

Thanks Jon. Yes, you did a video of it after you sent it out to have it repolished and the girdle cleaned up. You realize this stone/ring is hanging out at your shop right now, yes?

My ideal diamond would be one with the color of this old vintage (maybe even a bit more color), cut as a AVC (they truly have superior performance), with very strong florescence.

Demon: The collection of yours that you just described - wow.

Well, they're not very big, unlike your gorgeous avatar. The W-Z is .71, and they go down from there. I'm finding that the more colored diamonds I see, the less I like white diamonds. I'm also liking yellow gold more than white. Maybe I'm just feeling cold in my old age and am attracted to warmth, lol.

 

[Garry H (Cut Nut)]

In an earring the obstruction would be reduced and the blue zone smaller and less intense.
Garry, any opinion on what degree of obstruction to use in simulating earrings?

Hi Karl,
All the modelling that has been done is fundamentally flawed.
We (the Cut Group) have just published our first of a series major articles.
We took over the entire issue of the Australian Gemmologist. The topic is Human Vision.
This figure shows that for a close up (ring) viewing distance (12 inches / 30cm) that one eye can see lights from 6 degree so 12 degree is the realistic first level obstruction (from the side of the head). For earrings (as i always said) its way further and so I think a really useful model would be about 20 degrees.
Based on that a lot of my preference for shallower diamonds makes sense.

 

[Karl_K]

20 degrees obstruction for the above fic.
53t 36 crown 40.5 pavilion

 

[JulieN]

What was it above, 30? 35? That looks like a huge difference.

 

[Karl_K]

What was it above, 30? 35? That looks like a huge difference.

30 so 10 degrees less.

 

[Rhino]

Karl, Garry ... based on what we've gone over in this last topic, do you think these would be an accurate statements? If not how would you refine?


"The length of light rays in a diamond or the more it will refract within the diamond will cause color entrapment thus making a diamond face up to a stronger tonal color than how it may be graded in the face down position.
Jon inside the diamond the light is reflecting around, and sometimes small amounts 'refract out'. The internal reflections work like the difference between looking thru the side of a very tall glass of orange juice vs looking down from the top. When refraction happens (light is inside the critical angle of 24.5 degrees) there is a portion of the light escapes. Never all of the light can escape - at 90 degrees internal bounce 83% of the ray will exit but 17% will still reflect back inside the gem. If that happens then the ray could exit out the crown, and possibly in the direction of a light source, and so be brighter, or out the pavilion and be duller, darker, greyer or browner.

At the same time, while ideal cut diamonds appear whiter than their non ideal counterparts they will not necessary have color entrapment but will be perceived to be a lower color merely due to the fact that the ideal cut is reflecting back more bright white reflections than the non ideal. The areas of blatant leakage showing the color behind the diamond, while areas of secondary leakage showing a gray tonal colors.
I do not know what the definition of blatant and secondary leakage is Jon? All ideal cut diamonds leak. In the image you can see around 20% leakage in a default DC ideal cut.
Thoughts?

I'm happy to expound on my thoughts mate. Unfortunately DiamCalc 3.0 or 3.3 is not working on my Windows 8.1 laptop so I can't demonstrate but must refer to the graphics you guys have posted.

Primary leakage or blatant leakage: That leakage which occurs wherein we see bright whites in IdealScope/DiamXray/ASET with proper back illumination. Best demonstrated by yours and Karl's graphics that clearly show the color behind it. Ie. Karl's "tiffany blue" behind the diamond for example. We see this in general photography as well.

Secondary leakage: Those areas of leakage in fancy shapes and or fancy colors wherein light is traveling within the diamond across areas of leakage at a greater distance causing us to not clearly see the color behind it but "clouding" the view. In fancy colors increasing it's intensity. In shapes like pears, ovals, marquises, cushions, etc. which feature "crushed ice" appearances it will also enhance color in I/J colors when comparing to diamonds with ideal optics as these diamonds in I/J colors will certainly face up whiter.

Make sense?

Best regards,
Jonathan

 

[Garry H (Cut Nut)]

I understand Jon, but don't think we need another new definition - mainly because its almost impossible to define a boundary.
In the example I posted above for you, there is plenty of that going on in a well proportioned round brilliant. So a well cut round has both primary and secondary leakage.
Give me a model of your best stone and I will show you.
You did get SS's message with a new DC hasp download for Windows 8?
I sent you a message to your Rhinosrocks address

 

[Rhino]

I understand Jon, but don't think we need another new definition - mainly because its almost impossible to define a boundary.
In the example I posted above for you, there is plenty of that going on in a well proportioned round brilliant. So a well cut round has both primary and secondary leakage.
Give me a model of your best stone and I will show you.
You did get SS's message with a new DC hasp download for Windows 8?
I sent you a message to your Rhinosrocks address

Got it. When I'm in tomorrow I'll forward you a most awesome model.

 

[Karl_K]

I understand Jon, but don't think we need another new definition - mainly because its almost impossible to define a boundary.
In the example I posted above for you, there is plenty of that going on in a well proportioned round brilliant. So a well cut round has both primary and secondary leakage.
Give me a model of your best stone and I will show you.
You did get SS's message with a new DC hasp download for Windows 8?
I sent you a message to your Rhinosrocks address

Got it. When I'm in tomorrow I'll forward you a most awesome model.

Send it to me also please.

 

[Texas Leaguer]

This is a thought provoking and pretty wide ranging thread, but this comment is related to at least a couple of the subtopics.

I had never thought about this before in quite the same way, but expert cutting of fancy colored diamonds requires that certain aspects of light performance intentionally NOT be optimized. (I should state for the record that I am totally NOT an expert in this area).

It occurs to me that light leakage in a fancy can be highly desirable in certain cases. I think about the technique that is commonly used in setting fancy yellows where the jeweler takes a plate of high polish, high carat yellow gold and essentially molds the pavilion of the diamond to it. The reflections from the yellow gold greatly intensify the apparent color of the diamond.

This technique would then seem to have greater benefit to stones with greater amounts of leakage! Of course the cutter would have to achieve a balanced mix of optics so that you have cut driven color concentration and light return for sparkle. (Otherwise you have a glorified rhinestone).

I have a great respect for diamond cutters in general. But when you think about some of the challenges a cutter has in maximizing overall beauty in a fancy color, it really goes to another level.

 

[Karl_K]

I have a great respect for diamond cutters in general. But when you think about some of the challenges a cutter has in maximizing overall beauty in a fancy color, it really goes to another level.

They are optimized just not for the same thing.
What is interesting is that diamcalc color and the OctoNus color studies are making it more of a science rather than a rare art it always has been.
This has allowed more cutting houses to play in the colored diamond market.

 

[Rhino]

I understand Jon, but don't think we need another new definition - mainly because its almost impossible to define a boundary.
In the example I posted above for you, there is plenty of that going on in a well proportioned round brilliant. So a well cut round has both primary and secondary leakage.
Give me a model of your best stone and I will show you.
You did get SS's message with a new DC hasp download for Windows 8?
I sent you a message to your Rhinosrocks address

Got it. When I'm in tomorrow I'll forward you a most awesome model.

Send it to me also please.

Done.

 

[Karl_K]

based on the scan of a real diamond.
Blue to near blue is direct leakage, green and greenish blue are reflections of what is behind the diamond that has traveled through the diamond a greater distance.
One would have thought the leakage at the edge would be direct from the bottom and the arrow shapes would be more drawn from the opposite rear, however ......

 

[Rhino]

based on the scan of a real diamond.
Blue to near blue is direct leakage, green and greenish blue are reflections of what is behind the diamond that has traveled through the diamond a greater distance.

I hear ya ... if that was the case the distance is greater at that blue area where tips of the upper halves meet the star facet is and that is showing direct leakage.

One would have thought the leakage at the edge would be direct from the bottom and the arrow shapes would be more drawn from the opposite rear, however ......

Based on what we've been discussing I'd think the greenish areas by the edges is where direct/primarily leakage WOULD be except perhaps that there are light rays crossing into that area preventing the direct leakage. Hence the green. Garry?

 

[Garry H (Cut Nut)]

Jon I already mentioned I am not grading "degrees of leakage. Get off it, its way more complex and a simplification like that will rarley work.

I sent a ray through the left side leakage right next to the X in the dialogue box.
I will try to post 2 images - one at 14 bounces and one at 15 bounces. About 30% of the light is escaping on the 15th bounce.
It's complicated.


See how much leakage occurs in the next image!

 

[Garry H (Cut Nut)]

Stone rotated so the ray passes thru one of the small 8 leakage zones at the tips of the star facets. Jon you might have thought this is primary leakage.
But you will need to make a rule
e.g. when more than half the light entering or leaving exits the pavilion within X number of bounces (or whatever).
Let me know when you have a definition and I will ask Sergey why it won't work.... hahahaha

 

[Karl_K]

Stone rotated so the ray passes thru one of the small 8 leakage zones at the tips of the star facets. Jon you might have thought this is primary leakage.
But you will need to make a rule
e.g. when more than half the light entering or leaving exits the pavilion within X number of bounces (or whatever).
Let me know when you have a definition and I will ask Sergey why it won't work.... hahahaha

I would call those both indirect because the light is being drawn from the other side of the diamond in both cases.
Ok, I have the feeling the color test is not sensitive enough to tell direct leakage from indirect in all cases.

 

[Dreamer_D]

Here is a fun collage that shows the chameleon that is my L diamond. These photos are totally unedited. Top left was taken in a room with blue walls, top right in a room with pink walls, bottom left - yellow walls, bottom middle - ivory walls, bottom right - outside while snowing.



Great job...shows the real world, now would a 'D' show the same way?

My experience with a wide range of diamond tints is that more colorless stones don't show the same color shifting quality as more tinted stones. Of course, they show some! Perhaps the blue and pink would look similar in a D and L color stone. But in my experience, the more tinted stones take on taupe and yellow and brown MUCH more readily than colorless stones.