Grey in Idealscope

[echelon6]

Hi all

Could someone explain the attached idealscope pic to me? I''m interested in why there''s a ''dirty red'' colour under the table, like a mix of red and grey. What do theese areas indicate? And what is it caused by? Tilted diamond during camera shot? Or steep crown?

Thanks

 

[neatfreak]

I don''t know myself, but that is one nice idealscope image!

 

[chrono]

Maybe it is the lighting setup?

 

[risingsun]

I'm sure that John will be along soon and explain this to you. Have you considered calling WF and speaking with John or Brian Gavin directly about the IS and ACA cut? You can also do a search on IS images and find a lot of info on what constitutes ideal to poor...good reading

 

[strmrdr]

Small amount of leakage combined with the lighting environment and camera setup.
Can be seen on even the best stones if the lighting used is too bright.
What are the crown and pavilion angles?

 

[JohnQuixote]

Date: 7/27/2007 9:23:11 AM
Author: risingsun
I'm sure that John will be along soon and explain this to you. Have you considered calling WF and speaking with John or Brian Gavin directly about the IS and ACA cut? You can also do a search on IS images and find a lot of info on what constitutes ideal to poor...good reading

The angles are 40.8/34.8. What you’re seeing is a result of the current setup’s backlighting.

The diamonds below are 40.7-8 / 34.7-8 combos taken in setups as they have evolved over the years.The images look different but in person these diamonds are the same for all practical purposes.They have no visible leakage.

 

[Garry H (Cut Nut)]

There is no 100% light return - about 17% of light usually gets lost at many points where light can get in or get out of a diamond.
The light that goes out thru that area usually leaves at a lowish angle and hits the frosted perspex of the tray and heads along to the black edges of the circle of perspex (I made the trays that WF use). So you get more white from straight down leakage and more grey from sideways leakage

 

[JohnQuixote]

Here is a stone with an angle combo & pavilion issues that allow leakage through the pavilion.

 

[echelon6]

hmmm Very interesting, thanks all. Its interesting that Strm said all the best stones do have it, because I''ve seen many that dont (see link).

I''ve looked at some other diamonds held by WF (so that their idealscope images are directly comparable since its the same scope used each time) and I noticed that some diamonds don''t have this red-grey table area? (around 1 in 5 in my experience)

e.g. one of the best I''ve seen: http://www.whiteflash.com/hearts_arrows/A-Cut-Above-H-A-cut-diamond-66400.htm# - and its stats are great too - I have "number envy" of this stone!

Maybe its just a case of which side has the greener grass, but I always tend to notice that Sold stones tend to be of very high quality, even relative to the ACA standard.

 

[Garry H (Cut Nut)]

If you care to research the point where grey becomes percieved at 1/2 way between black and white you will find it is about the point where about 18 or 20% of black is added to white. (try wiki).

The same is true with ideal-scope pink - what looks like 50% light return is actually much higher. So your over analysis of shades of photographs is totally useless as a means of making decisions

 

[strmrdr]

Date: 7/27/2007 9:46:40 PM
Author: echelon6
hmmm Very interesting, thanks all. Its interesting that Strm said all the best stones do have it, because I''ve seen many that dont (see link).

I''ve looked at some other diamonds held by WF (so that their idealscope images are directly comparable since its the same scope used each time) and I noticed that some diamonds don''t have this red-grey table area? (around 1 in 5 in my experience)

e.g. one of the best I''ve seen: http://www.whiteflash.com/hearts_arrows/A-Cut-Above-H-A-cut-diamond-66400.htm# - and its stats are great too - I have ''number envy'' of this stone!

Maybe its just a case of which side has the greener grass, but I always tend to notice that Sold stones tend to be of very high quality, even relative to the ACA standard.

Re-read what I said, under specific conditions, then read why in what Garry said, brighter lighting makes partial leakage look worse.
John can answer the question of how many different set ups they currently have but there will be a variation between each of them even with the same stone.
Thats why its a pass fail test and not abcdef

 

[strmrdr]

Date: 7/27/2007 9:46:40 PM
Author: echelon6


e.g. one of the best I've seen: http://www.whiteflash.com/hearts_arrows/A-Cut-Above-H-A-cut-diamond-66400.htm# - and its stats are great too - I have 'number envy' of this stone!

That one has a lot less intense backlighting, put it with the same backlighting and it will look similar except for the effects of the mild painting in the second.
The first one has over bright lighting and this one could be turned up a notch to make the leakage stand out more without over blowing it.

 

[strmrdr]

Date: 7/27/2007 6:20:17 PM
Author: JohnQuixote



The angles are 40.8/34.8. What you’re seeing is a result of the current setup’s backlighting.

agree.
Should have know what the angles where if id thought about it LOL

 

[echelon6]

Strm, I have a long way to go before I can guess cp angles by just looking at their IS image

 

[Garry H (Cut Nut)]

We get good at estimating patterns

plus http://ideal-scope.com/Using%20DC_files/frame.htm

 

[strmrdr]

Date: 7/27/2007 11:42:18 PM
Author: echelon6
Strm, I have a long way to go before I can guess cp angles by just looking at their IS image

its an ACA so there is a large chance it averages 40.8/34.8 with an occasional 40.7 and 40.9 and rare 40.6 in the mix for the pavilion and a 34.7,34.9 and rarely a 35 for the crown in the mix.

 

[echelon6]

Yeah I noticed that about ACAs, I never quite understood why ACAs tend to average 34.8 / 40.8 when Tolkowsky''s crown is 34.5 (iirc)...

Gives me the impression all the TIC ACAs have been sold

 

[strmrdr]

Date: 7/28/2007 2:36:11 AM
Author: echelon6
Yeah I noticed that about ACAs, I never quite understood why ACAs tend to average 34.8 / 40.8 when Tolkowsky''s crown is 34.5 (iirc)...


Gives me the impression all the TIC ACAs have been sold

nope, Brian''s preferred combo is slightly different than tolk.
Which is what an ACA is, Brian''s preferred combo.

 

[echelon6]

then ACA''s should be renamed to BICs

 

[risingsun]

They are also called BB''s [Brians''s Babies]