Table Reflection Question

[Detox]

When viewing a round brilliant diamond when would you expect to see the reflection of the entire table? I have read several articles/tutorials that state that on an ideal/excellet cut diamond the table will appear smaller than it actually is. Does the tableonly look smaller when viewed from the top looking down? If you twirl the diamond in the light would you expect to see a reflection of the full table at times? Should you never see a reflection of the entire table on an ideal/excellent cut diamond?

This question might seem trivial, but seeing as I don''t have a diamond infront of me I am unable to tell based on internet photos.

Cheers,

Detox

 

[RockDoc]

Dear Detox

The table of an ideal cut stone should BOW INWARDS. The table is basically two square shapes and each side of the two sqaures should bow inwards on a stone with a 59% table or less.

If the sides are straight then the table is probably 60-62%. If the table BOWS OUT, then it is 63% or more.

This estimation of table size is for ROUND STONES ONLY.

You should not see a circle that appears "frosty". If you see this, the diamond is what is called a fish eye. What this is is the reflection of the girdle at the edge of the table. This is a negative attribute. In order to see the girdle reflection in a well proportioned diamond, you tilt the diamond until you see it. In a well cut stone the girdle won''t appear until it is tiled about 15 degrees.

You will also see what I call the Pavilion Depth circle. This is an image that is a circle near the point ( culet ) of the stone. This image should appear as a small circle. Generally, the larger the circle the deeper the pavilion is.

Practice and viewing a decent number of stones will get you up to snuff with this.

Hope this helps.

Rockdoc

 

[Detox]

Thanks for the response. I think from what I have read I do understand about the "fish-eye" effect.

What I was referring to is similar to what is photographed in this thread by "slmulkey"

https://www.pricescope.com/community/threads/picture-of-my-ring.3963/}
I know this was a photograph, but my the idea of seeing the table as a reflected solid piece of glass is the concept I was referring to.

So, if the stone is ideal cut and you tilt it under bright light can you expect to see this. (ie. instead of the the table looking like it bows inwards it looks like a flat surface)

Just curious.

Detox

 

[RockDoc]

I think what you might referring to when the light shines on the table at a specific angle it glares out the facet. If you hold the diamond in a position where the light is at a particular angle to the diamond facet - the glare can occur on any facet - not just the table facet.

That appears to be what is happening in that photo.

That photo image is no where near correct for approximating the table size of the stone

Maybe I misunderstand what your question or answer is ...


Rockdoc

 

[valeria101]

Date: 8/17/2005 1:37:07 PM
Author: Detox

I know this was a photograph, but my the idea of seeing the table as a reflected solid piece of glass is the concept I was referring to.

Sure. At some angle you get a flash from reflected light - that that bounced off the table''s surface without entring the diamond. It happens for every facet, only their position and much smaller size does not help show that at all. The table does. The largefacets of step cut diamonds show these reflections more.

As much as I can tell...

It is difficult to capture the effect in a static picture because tge range of positions where the flash would be caught by the camera is very narrow. Using the flash does not help either because then the light is too darn strong. But a movie does show it rather well, and some sellers present their diamonds like that.

Here''s one EXAMPLE - it is easy to see the respective flash, IMO.

A ray trace model will show the same by numbers too (there is one here).

Is this what you are talking about ? I wasn''t sure... but this is the first time that the question occurs, hence the post.

 

[valeria101]

Have a picture but for some reason I cannot post it - for the first time since I joinced this forum !

... must be the darn firewall.

 

[valeria101]

this should have been attached to the previous post...

 

[diamondsrock]

I''m having a hard time understanding the table bowing inwards or outwards concept. Can you post a pic or illustration to show me? From looking at my diamond with the unaided eye, how best to approximate the table dimension? I''m curious because I don''t have a table % on my diamond.

 

[RockDoc]

Date: 8/17/2005 6:55:03 PM
Author: diamondsrock
I''m having a hard time understanding the table bowing inwards or outwards concept. Can you post a pic or illustration to show me? From looking at my diamond with the unaided eye, how best to approximate the table dimension? I''m curious because I don''t have a table % on my diamond.

This can''t be done with the unaided eye.

If you want an estimate of it you''ll need a good quality diamond loupe with a triplet lens.

If you want to know less "approximately" it will need to be measured with a special microscope eyepie, a proportion scope or a table guage.

If you want really precise info and measurement getting a Sarin repoe it the best way to accomplish ths.

You need to know where to take the measurements ( 4 of them ) from, and it is sort of tricky for a novice to do.


Rockdoc

 

[Mara]

Yep smulkey''s pic is just the angle that the stone was photographed at. Sometimes depending on how my hand is and my eye in relation, I can see the flat surface of my table on my ideal cut stone. The larger the table, the bigger the surface! Having had a 62% table previously, now my preference is for smaller tables, so my stone now is a 55% table I think.

 

[EZ]

Date: 8/17/2005 6:55:03 PM
Author: diamondsrock
I''m having a hard time understanding the table bowing inwards or outwards concept. Can you post a pic or illustration to show me? From looking at my diamond with the unaided eye, how best to approximate the table dimension? I''m curious because I don''t have a table % on my diamond.

Will the bad illustration in this thread help?

If you look closely you can see the "white" lines that represent the table are bowed in fromthe straight lines that I drew to outline the two ''squares'' on the table. It is not an extreme bow, but it is there. A table of greater than 60% will have the bow facing the other way. I doctored that image from the idealscope image supplied with my diamond. To see the bows on your diamond you will probably need magnification.

Does that help?

 

[diamondsrock]

That''s pretty cool, EZ. Now I understand what the concept is. I have a hard time visualizing things. Thanks.