Optical analysis of mounted diamonds

[denverappraiser]

8.28 x 8.34x5.09mm
V.Thin - Med girdle

I've been practicing with IS photography. I can do the same general thing with h&a but I happened to have an IS cone handy and this is a skill I'm working on anyway. It's getting better. This is a stone that just happened to pass through my hands. As you can tell, it's not especially good but, for the purposes of this thread, most of the stones out there aren't particularly good.

Neil

 

[Garry H (Cut Nut)]

Here you are Neil.
Some little greay shadows in the table are not matched up.
If you are using the ideal-scope lens - then I would drop it.
Your back light seems to be about right.

 

[Garry H (Cut Nut)]

Here is the modeled ideal-scope from DiamCalc

 

[denverappraiser]

Date: 12/27/2004 5:34

3 PM
Author: Garry H (Cut Nut)
Here you are Neil.
Some little greay shadows in the table are not matched up.
If you are using the ideal-scope lens - then I would drop it.
Your back light seems to be about right.

No lens. I took it through an opaque tube about 2 inches long. It''s taken through a watch crystal that is mounted in the base of the IS cone to get the stone level to the table.

Neil

 

[Garry H (Cut Nut)]

Glass between the scope and the stone is not good.

Do you know or can you have the stone measured Neil?

 

[denverappraiser]

I did a Sarin on it but I didn''t think to copy the data before I delivered it to the client. He picked it up while I was typing the last message.

I expect to see him tomorrow and I''ll snag a copy.

Perhaps a camera filter would work better than the watch crystal. Hmm. Maybe a red filter

Neil

 

[Garry H (Cut Nut)]

Nup - there should be no glass between the stone and the red reflector.

 

[denverappraiser]

The red filter was a joke, sorry. The point of the piece of glass (or something) is to get the image lined up perpendicular to the table. This seems critical for the kind of analysis at hand. No? The H&A image requires that all backlight be eliminated. This is almost always out of the question for mounted goods, which is why I''m still playing with the IS dispite Sergey''s comment that DiamCalc prefers h&a images.

Neil

 

[Garry H (Cut Nut)]

Neil if you do not wish to buy the full ideal-scope lighting environment, then for $100 you can buy the tray only from www.ideal-scope.com.

 

[denverappraiser]

Garry,

I hadn't seen those. It's true that I'm a bit set back by the price of the photo system and the trays may include the answer to my questions. It strikes me that it's important to understand what is going on if I'm going to get anywhere with this train of thought. Do they work with mounted goods?

Sorry if I'm being a pest.

Neil

 

[Garry H (Cut Nut)]

For mounted goods you can remove the tray and just stand the ring on a backlight and take a photo.

 

[JohnQuixote]

Neil, you have made kind comments about our photography before. FYI, we use Garry's "Rapid Photo System" tray for making images. It has made a tremendous difference in the quality and readability of those photos.

He may have given info, above, but I have links handy and only a minute to post. Please forgive any redundancy.

Specific info on tray and how to use.

I made a diagram with speculations for another thread comparing photography of IS images (a) with glass between IS and stone versus (b) IS flush with stone (attached).

 

[RockDoc]

Date: 12/27/2004 8:26:42 PM
Author: JohnQuixote
Neil, you have made kind comments about our photography before. FYI, we use Garry''s ''Rapid Photo System'' tray for making images. It has made a tremendous difference in the quality and readability of those photos.

He may have given info, above, but I have links handy and only a minute to post. Please forgive any redundancy.

Specific info on tray and how to use.

I made a diagram with speculations for another thread comparing photography of IS images (a) with glass between IS and stone versus (b) IS flush with stone (attached).

Item B (your graphic

Appears to be identical to how the Firescope is set up.

I get great photos with the Firesscope but I can''t achieve any where near the detail using the ideal scope.
I do have back lighting and have even used the tray from the Firescope to hold the stone level and steady - but still no luck.

Got any suggestions?

Rockdoc

 

[JohnQuixote]

Bill,

One thing the diagram did not show is that we use a closed, controlled environment. No other light source can possibly interfere. Beyond that, our results may be specific to the illumination level, camera/lens and focal depth used. I'm away from the office right now, but can get back to you with more later.

 

[Garry H (Cut Nut)]

Rocdoc it is better to completely flood the stone holder tray by sitting it right immediately on top of a larger flat light of the type used for slide and xray transperancies - bigger versions of our ideal-light shwon above. The Firescospe and John''s demo sketch show the light localised and further away - this only shows light leakage from directly below - when you examine an 8* with the setup we recomend you will find more leakage than with the Firescope.
http://www.ideal-scope.com/manuf_iscapture.asp
This shows our setup. you do not need our tray if you only wish to do red reflector photo''s. but our tray also works well for realistic photo''s too.

 

[valeria101]

Date: 12/27/2004 5:34:3 PM
Author: Garry H (Cut Nut)
Here you are Neil.
Some little greay shadows in the table are not matched up...Your back light seems to be about right.

Well, this post brings up another problem about Iscope use: how to standardize lighting conditions for commercial presentation and what not.

Obviously, it would be nice to have a serious-looking system that comes calibrated from the manufacturer. But then, the main attraction of this little tool gets lost: it would not longer be either nearly costless not usable by buyers. As soon as a professional version gets way different from what customers may use, this would be just another branding machine.

But the Gem Adviser already produces perfectly calibrated Iscope images, right ? The post cited here compares an Iscope picture with the GA model to conclude if the lighting conditions were ok. Why could not the same procedure be presented as a way to "calibrate" Iscope pictures and make them comparable from one source to the next ?

 

[Garry H (Cut Nut)]

weezz workin on it Babe

 

[denverappraiser]

Garry,

The stone in the photo above is Round brilliant cut
8.28 x 8.34 x 5.09mm
Table: 58.8%
Crown: 15.0% 35.0 degrees
Pavilion 43.4% 41.2 degrees
Culet V. Small
Girdle 0.5%-1.6% v. thin - medium

Neil

 

[valeria101]

Date: 12/28/2004 1:44:32 PM
Author: denverappraiser
Garry,

The stone in the photo above is Round brilliant cut
8.28 x 8.34 x 5.09mm
Table: 58.8%
Crown: 15.0% 35.0 degrees
Pavilion 43.4% 41.2 degrees
Culet V. Small
Girdle 0.5%-1.6% v. thin - medium

Neil

The guesstimates are about 2 tenth of a degree apart - probably closer than two independent Sarin readings, if I am not wrong ...

Would it be useful to compare the GA guess with the variations registered by a 3D scan ? Bet' the GA falls next to the median, if anyone has the heart to put up a sample.

 

[Garry H (Cut Nut)]

Thanks Ana.

Actually I am going to stick with my proportions over the sarin result because when i model those proportions with DiamCalc the leakage is much worse than the actual photo.

 

[denverappraiser]

I"m back like a bad penny.

My IS pictures have improved but I'm still having problems with matching the wireframe to the image. I can't use the tray system for this task because the whole objective is to use it for mounted stones. I"m using the reflective glare between the table and the camera lens to try and get perpendicular. Any thoughts on this technique?
An arrows picture has an even worse problem because it's necessary to eliminate the backlight, something that seems nearly impossible on a mounted stone. I still think this has promise but I think the IS and DC is going to be the key.

After a bit of practice at this, I have a few specific questions:

In the models that Serg and Garry have done above, the DC image matches the outside of the stone exactly. When I try to match it in the program I can only zoom in and out with discrete steps and I can't change the background image at all. I can use photoshop to change the image externally but it also must be absolutely centered to line up properly. How did you get the two images to line up so well?

DC seems to assume that the pavilion and crown are properly registered. This is not always the case with stones that come through in mountings. Am I correct that this is something that can't be changed in the model? The DC model I make suggests that this stone has some pretty serious crown symmetry problems but it doesn't really look all that bad when I look at it. Is this a problem with my photo and is there something I can do to tell the difference between a bad pic and a bad stone?

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[jpinsly]

Bringing back an old thread..

Can someone please help me approximate the crown and pavillion angles, along with table and depth?

 

[Serg]

Neil,

re:In the models that Serg and Garry have done above, the DC image matches the outside of the stone exactly. When I try to match it in the program I can only zoom in and out with discrete steps and I can''t change the background image at all. I can use photoshop to change the image externally but it also must be absolutely centered to line up properly. How did you get the two images to line up so well?

You can :
1) Move photo in "Picture/Adjust position" mode
2) Change mass( diameter) of model

 

[valeria101]

Date: 12/3/2005 9:04:42 AM
Author: jpinsly
Bringing back an old thread..

Can someone please help me approximate the crown and pavillion angles, along with table and depth?

It would be hard starting with your picture... there''s too much going on because of multiple light sources. The angles result from matching exactly reflections inside the stone - in an Ideal Scope picture, a few important ones get highlighted, in a picture in natural lighting there are hundreds of little shards to deal with - it would be a full fledged research project (for me, at least)