How lighting can influence on grade appearance

[michaelgem]

from michael: . ">>> Michael Cowing

Diamondsrock asks: ok, so now as a regular consumer I am completely confused. The most beautiful diamond I have seen (at least in pictures) on Pricescope had crown 34.1 and pav. 41.0. Is this considered a shallow stone and are you saying it will have less brilliance?

P41Cr34.1 is great combination. Sergey Sivovolenko

Sergey is right, P41Cr34.1 is an Ideal combination for the 16 main facets. Any round brilliant that is cut this way is a potential super ideal providing that the symmetry and other 41 facets are also in the range of Ideal.

My above statement is a matter of degree. The ‘sweet spot’ for Ideal is not a point such as Tolkowsky’s P40.75Cr34.5, which was arrived at with a questionable math-physics argument. The sweet spot extends in a non-uniform way centered on Henry Morse’s P41Cr34-35.

Tolkowsky knew this and even says so explicitly and implicitly in his book. IMO the only reason he changed from 41 to 40.75 was to accord with his now questioned derivation.

The fact that Diamondsrock sees P41Cr34.1 as “the most beautiful diamond I have seen” is to be expected if those like myself espousing Morse’s and Tolkowsky’s range of main angle combinations are correct.

Michael Cowing

www.acagemlab.com

 

[strmrdr]

Date: 1/18/2006 10:21:33 AM
Author: diamondsrock
from michael: <<<''(iv) With the pavilion angle held close to 41°, crown angles below Tolkowsky''s 34.5° yield decreasing brilliance under close-up observation in spite of the fact that they show increasing WLR in hemisphere illumination. With a pavilion angle near 41°, shallow crown angles are not a direction to go in search of greater brilliance. ''>>>


ok, so now as a regular consumer I am completely confused. The most beautiful diamond I have seen (at least in pictures) on Pricescope had crown 34.1 and pav. 41.0. Is this considered a shallow stone and are you saying it will have less brilliance? These are the angles I was shooting for in my next stone but now I''m confused!

I haven''t seen one yet with these angles anyways in all my searches through vendor inventories here but I was thinking if one came up I would be interested. NOw I don''t know.

That is one of my favorite combos as long as the LGF is fairly long (78%+) and the diamonds angles fairly tight.
GOG has some diamonds in that combo often.
Iv seen a few in person with that combo and they are my favorites.

 

[Garry H (Cut Nut)]

Date: 1/18/2006 8:27:03 AM
Author: Yuri
This is a picture of Magna Colorscope, Eickhorst System production, an observer, and the set of stones under discusion. One upper light is turned on.

Thank you Yuri. Nice hair.
I have put the 2 photo''s together. You can see that even with the Echorst light turned on that there is still a lot more light in your environment than the background light in the GIA example - there could be different levels of eye adaption?
It is also interesting that the Echorst tube is about 1/4 the distance from the diamonds. If the tubes were the same brightness then there would be 16 times more light in the Echorst.

 

[Yuri]

Here is a pair: real photo and DC model to compare. Lighting conditions are similar with Magma Colorscope and results are similar too.

 

[Yuri]

Attached is a GemAdviser file of the same stone in the same light.

 

[diamondsrock]

not to split hairs here, but can someone tell me how a 34.1 crown 41.0 pav. stone would differ in visual appearance from a 34.4 crown 40.8 pav.? Or from a 34.8 crown 40.7 pav.?

 

[strmrdr]

Date: 1/18/2006 4:13:07 PM
Author: diamondsrock
not to split hairs here, but can someone tell me how a 34.1 crown 41.0 pav. stone would differ in visual appearance from a 34.4 crown 40.8 pav.? Or from a 34.8 crown 40.7 pav.?

in order to answer that a lot of assumptions have to be made.
1> lgf% of 78%
2> stars of 50%
3> "classic" style girdle treatment on all.
4> equal hearts

34.1/41 slight white light return over colored light return but can still have kicken fire

34.4/40.8 more of the same but not as much so as the first one

34.8/40.7 slight colored light return over white light return but still can be very bright.

In all 3 cases it would be a personality difference rather than a quality difference.
There are other factors that could change things slightly and often all the other factors arent even so its really a diamond by diamond comparison but if you took a bunch of each and averaged it out thats the way I think they would fall.


The differences wouldnt in almost all lighting conditions be enough that you would say that one rocks and that one sucks but the difference might be enough that you would say I love that one more than the others.

 

[diamondsrock]

that''s what I thought someone would say in general terms. Thanks. Since I value white light more than fire I can see why the first one spoke to me and why the others don''t as much. To me an ideal diamond would be bright and have good scintillation (very important - I would want it to dance in the light) and average fire.

 

[Serg]

re:You can see that even with the Echorst light turned on that there is still a lot more light in your environment than the background light in the GIA example - there could be different levels of eye adaption?
It is also interesting that the Echorst tube is about 1/4 the distance from the diamonds. If the tubes were the same brightness then there would be 16 times more light in the Echorst.

1) What is wall brightness in office light( correspondent to GIA background)?
2) GIA DOC light has very bright vertical zone close to lamp. Eye could you use this zone for adaptation , in this case level of eye adaptation is same for both light schemes.