What is contrast?

[Ashleigh]

Hi, I''ve posted on another thread about a stone I put on hold: http://www.goodoldgold.com/diamond/4775

I just realised that there''s info called Contrast posted on the website. Other GOG stones seem to have mostly constrast 0 but this one I''m interested in has contrast 0.23.

From reading Jon''s tutorial, it seems contrast is impt for the stone to appear large to eyes. I picked 0.95L (6.35mm*6.38mm) over 0.96K (6.31mm*6.34mm) as the L has greater spread though smaller carat weight. But if the 0.95L has contrast 0.23 while 0.96K has contrast 0, will L look smaller than K to eye?

This''s the 0.96K: http://www.goodoldgold.com/diamond/4536/

Please help me out here cos I''m anxious to know the answer so didn''t email Jon this qn as he''ll re-open only on 6 Jan. Thanks

 

[strmrdr]

contrast is blue and white in the ASET on the report.
AGS discounts for to much or to little.
Since there is little white and what is there is expected they nicked it slightly for either to much or to little blue.

If it isn't enough to kick it out of the 0 range then it isn't enough to worry about.

 

[Ashleigh]

Hi Storm, thanks for the reply

I''d never have connected what I read from tutorial to what you said. In this case, I understand the amt of white (leakage for contrast to happen) is expected. But what does blue colour do? More blue means more dark areas and less blue means less dark areas? As you mentioned, since it''s still in 0 range, it shd be alright. But is there a way to tell if it''s too much or too little blue in this case?

 

[strmrdr]

this image shows what the colors mean...

But the catch is that the AGS software calculates its own virtual ASET image which hardly ever matches actual aset images or images created by DiamCalc,,,,
It is shown below...

 

[Garry H (Cut Nut)]

its a very complex issue.
The blue area will turn very very bright red in the ASET when you move the stone, and this then becomes scintillation of the most scinillating type (it is one of the reasons I prefer slightly shallower stones - because the higher angle light return has more sizzle when you see a tilted stone face up).

AGS try to do it - but until they have a method to assess scintillation, they have no bullets - let alone the silver one (which is what the scintillating facets look like)

 

[Ashleigh]

Hi Storm and Garry, thanks for the replies.

I appreciate that you both took the time to answer my question but I don''t really understand the answers.

I think this issue is too hard for a layman like me to understand. So I''l just accept that contrast in the 0 range is still good. Thanks