Fire in an American Ideal Cut Diamond

[michaelgem]

Check out the fire in this American Ideal cut diamond at http://www.acagemlab.com , enter and click on the HOT TOPIC icon for more American Ideal fire pics.

Michael Cowing
ACA Gemological Laboratory

 

[Garry H (Cut Nut)]

Hi Michael

What's cookin?

Cheers

 

[Rhino]

Absolutely gorgeous pics Mike. Did you get a chance to see the pics I've taken with my new rig? They are posted on this link. https://www.pricescope.com/community/threads/diamond-photography-competition.9751/




I'd like your input positive or negative.




Warm regards,
Jonathan

 

[Rank Amateur]

Nice photos. Nice explanation.

What exactly is the American Ideal? Was it Americans who refined the cutting/proportioning process?

 

[valeria101]

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On 11/1/2003 4:06:31 PM michaelgem wrote:


Check out the fire in this American Ideal cut diamond at http://www.acagemlab.com .

Michael Cowing
ACA Gemological Laboratory
----------------

Hi!

Ok, those diamonds and their pictures are a fine thing, but it was that picture of Guatemalan Jadeite that got me in trouble! I had no idea that source produced such fine quality... What would be a god source of info about this source? Who is to 'blame' for that unusual carving? Both me and my little jade collection would be very grateful for your answer

PS: I've sent an e-mail along these line too...

 

[Garry H (Cut Nut)]

Michael do you think it is possible that some of the colors we can see in the diamond are a result of the fact that light can get in the pavilion of the diamonds in the way that these beautiful photographs have been taken?

It has been our experience that firey photo’s are very hard to achieve when we place stones in darkened seating holes so absolutely no light can get in the back.

If you follow the thread Rhino suggested you can see what we mean.

 

[Iiro]

Hi Michael,

Thanks for the link.

Was there two different diamonds in the pics?

Did you try to demonstrade the difference of these two?

Why the diamond on the upper right did not had blue backround?

Iiro

 

[michaelgem]

Hi Garry,

Relating to my post: Check out the fire in this American Ideal cut diamond at http://www.acagemlab.com , enter and click on the HOT TOPIC icon for more American Ideal fire pics, You asked:
Michael do you think it is possible that some of the colors we can see in the diamond are a result of the fact that light can get in the pavilion of the diamonds in the way that these beautiful photographs have been taken?

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

In the referenced article I note that the photography and analysis was inspired by Bruce Harding's question : "Pretty. What is the source of the large color patches?".

The answer is fire, dispersed by the diamond from open sky daylight, which was the source of this diamond’s illumination. The daylight was broken up to get this degree of fire in a manner that often happens in natural viewing environments. This was how the diamond appeared to my eyes, as I took the photograph.

Because the diamond was on blue-fluorescing laser print paper, the camera recorded a blue fluorescent background, while my eyes saw the paper as white.

Any light leakage, which is better described as reflections coming to our eyes from beneath the diamond, would have that blueish tint. You can see some blueish light leakage just above the patch of red fire.

All the spectral colors such as this patch of red and the deep blue, yellow and green fire are the result of contrasty illumination, the kind you might encounter in a restaurant or theatre with many tiny ceiling spotlights. DiamCalc's disco lighting is a simulation of this sort of contrasty illumination necessary to the observation of fire potential in a diamond cut.

Best regards,

Michael Cowing
ACA Gemological Laboratory

 

[michaelgem]

Hi Iiro,

Did you see the wonderfull Northern Lights show a few days ago? Your location up North should have been ideal. Anyone who missed them should check out http://science.nasa.gov/spaceweather/aurora/gallery_01oct03_page8.html for some otherworldly pics.

You asked:

Was there two different diamonds in the pics?

Actually there are three different diamond's present in those pics, all are American Ideal except for the three-diamond, ring pic.

Did you try to demonstrate the difference of these two?

The one pic of two American Ideal cut diamond's illustrates the different properties of the mosaic pattern of reflections in the face-up view of one with and one without the property called optical symmetry.

Why the diamond on the upper right did not had blue backround?

The blue background occurred inadvertently from blue fluorescent laser print paper. The diamond's in the other pics had non-fluorescent backgrounds to avoid this problem.

Best regards,

Michael Cowing
ACA Gemological Laboratory

 

[Garry H (Cut Nut)]

Thanks Michael,
But are you sanctioning light entering from behind a diamond?

What about different types of settings for different types of diamonds?

For instance I have long belived that steep deep leaky diamonds can best be set in high white gold 4 prong rings (not platinum as the prongs need to be thicker).

But how do you feel about promoting a cut - the American ideal - on the basis that it is firey because of light that has entered from underneath - what we usually call leakage?
And what about those who set them in ways that do not allow light to enter this way - as is very often the case?

And finaly - is it ethical to promote diamond with pictures taken this way? I have for instance often taken issue with Brad and Jan for presenting photo's of diamonds in this manner. The deep leaky stone attached caused quite a bit f a stir over a number of years.

 

[mdx]

But how do you feel about promoting a cut - the American ideal - on the basis that it is firey because of light that has entered from underneath - what we usually call leakage?

----------------------------------------------------

This could be an interesting debate


Wayne

 

[michaelgem]

Hi Garry,

You asked:

But are you sanctioning light entering from behind a diamond?

How do you feel about promoting a cut - the American ideal - on the basis that it is firey because of light that has entered from underneath - what we usually call leakage?

And finaly - is it ethical to promote diamond with pictures taken this way? >>>>>>>>>>>>>>>>>>>>>>>>>>>

As you know, we can't sanction or not sanction light leakage in a diamond cut, as it happens to some degree in all diamond cut designs.

Whether the cut is American Ideal or your FIC or BIC or to coin a term, SDC, Steep-Deep Cut, all these cuts increasingly reflect light from below the stone when tilted (leak light).

Most of the loss in brilliance is in the quarter moon inverted crescent area between the table edge and the girdle reflection. (The girdle reflection passes along the bottom edge of the red fire patch, so the red fire is in this crescent area.

However, the red fire and the other patches of green, yellow and blue fire resulted from light entering the diamond from above, not below. They are not due to light leakage.

This pic is of an American Ideal cut diamond. Notice I said in my Hot Topic article at www.acagemlab.com that:

This picture illustrates the American Ideal cut’s beauty with respect to both brilliance and fire. The American Ideal is superior not only with respect to contrast and light return brilliance in lighting favorable to these qualities and quantities of diamond beauty, but also with respect to fire when the lighting is favorable to this important and often unheralded aspect of diamond beauty.

Best regards,

Michael Cowing
ACA Gemological Laboratory

 

[michaelgem]

----------------
On 11/1/2003 5:34:45 PM Rhino wrote:


Absolutely gorgeous pics Mike. Did you get a chance to see the pics I've taken with my new rig? They are posted on this link. https://www.pricescope.com/community/threads/diamond-photography-competition.9751/


I'd like your input positive or negative.


Warm regards,
Jonathan
----------------

Hi Jonathan,

It has been too long since we last chatted.

The pic you displayed, taken with your new equipment, is gorgeous.

I believe I understand how the red fire occurred, but the green reflection that appears to be an external reflection off an upper girdle facet has me puzzled.

Great job.

Best regards,

Michael Cowing
ACA Gemological Laboratory

 

[Colored Gemstone Nut]

Interesting Michael,




Just a side note about a diamonds fire in certain light conditions....




My Fiance (Regina) and I were eating dinner under our kitchen table light. Soft abient light and the light bulb is covered by a cream colored globe.




She has an ideal cut hearts and arrows stone in a vatche x-prong setting (mounted low) but full view of the pavilions and good coverage of the girdle is present....




I can really appreciate the light return from direct overhead view, but the other night I noticed when she has her hand tilted a little at an angle more fire (white light) seems to be present and the stone does not take on the traditional round shape when viewed directly overhead but seems a little oblong and the fire is even more evident and makes the diamond more pronounced. Is this because light conditions are favorable and overhead shadow which might create more of a contrast is not present because I am viewing the diamond from an angle...??

 

[Garry H (Cut Nut)]

----------------
On 11/3/2003 11:31:40 PM michaelgem wrote:

Hi Garry,


Most of the loss in brilliance is in the quarter moon inverted crescent area between the table edge and the girdle reflection. (The girdle reflection passes along the bottom edge of the red fire patch, so the red fire is in this crescent area.

However, the red fire and the other patches of green, yellow and blue fire resulted from light entering the diamond from above, not below. They are not due to light leakage.

Best regards,

Michael Cowing
ACA Gemological Laboratory----------------

I am not so sure that the fire in the region you refer to is supplied from above the stone michael.
I think I found a use for the gIA's lighting model - this is a hemispherical DiamCalc dome lighting (with no head / camera) and no COS.
It shows the region you refer to as being rather dark, indicating that we are 'seeing' out the back.
What do you think?

My comment with regard to misrepresentation came obout from one of the reasons I started this photography thread.
We are trying to produce a standardised set of lightings that if adopted, would honestly and fairly represent diamonds to consumers (or the trade). Jonathon / Rhino introduced some colored backgrounds that help the fire along. these are great for brochures and advertising shots - but would you think it was a fair way to represent diamonds commercially?

 

[Iiro]

Hi Michael,

no I did not see the Lights, it was too cloudy here. When winter comes we will have better change to see them. Right now it rains every day.
---------- Michael-----

The one pic of two American Ideal cut diamond's illustrates the different properties of the mosaic pattern of reflections in the face-up view of one with and one without the property called optical symmetry.

______-----------

Judging by these pics the fire in the non symmetrical diamond is prettier. Does your eyes tell the same thing when comparing these two in the identical lighting environment?

Can you tell how the American ideal differs from AGS 0?

 

[Serg]

Hi, Michael
Did you use aperture before lens?

 

[michaelgem]

----------------
On 11/4/2003 1:20:06 PM Serg wrote:

Hi, Michael
Did you use aperture before lens?----------------

Hi Serg,

I used a close up lens with its aperture and used extensions to get the magnification I needed.

Michael Cowing
ACA Gemological Laboratory

 

[michaelgem]

----------------
On 11/4/2003 8:25:53 AM Sibelius wrote:

Hi Michael,

You said: The one pic of two American Ideal cut diamond's illustrates the different properties of the mosaic pattern of reflections in the face-up view of one with and one without the property called optical symmetry.

______-----------

Judging by these pics the fire in the non symmetrical diamond is prettier. Does your eyes tell the same thing when comparing these two in the identical lighting environment?

Can you tell how the American ideal differs from AGS 0?----------------

Great questions Iiro,

I could cover pages with a complete answer, but it would take too long to write and few would have the patience or interest in reading it.

Briefly, a non-optically symmetrical American Ideal like the one on the left has more numerous and smaller reflections of brilliance and fire, while the optically symmetric American Ideal has larger reflections in the face up normal viewing position due to the precise facet alignment.

Notice the large flash blue fire from the symmetric right diamond's mains. The greater break up of the reflections occasioned by the lack of optical symmetry can contribute to greater scintillation, and at the same time reduce the perception of fire. Especially in smaller sizes, the broken up fire may be too small to register as color to our vision or it may add back to white with visual merging of adjacent reflections like the rgb color guns of a monitor.

I like to present these ideas, and let my client decide which he or she prefers. There is no substitute for observation of the diamond's optical performance in as many realistic lighting and observation circumstances as possible.

This side-by-side normal view in diffuse blue-sky daylight with the viewer's head and torso obstructing the daylight from his/her direction is one such realistic circumstance.

Best regards,

Michael Cowing
ACA Gemological Laboratory

 

[Rank Amateur]

Is "American Ideal" per the AGS 0 definition?

 

[beryl]

Michael:
> I like your last response to Iiro just above - especially the comment re optically aligned vs mis-aligned cuts.