How do you take various CUT pictures?

[Regular Guy]

Date: 12/11/2006 12:01:32 PM
Author: denverappraiser

Here’s my problem with the current state of ASET photography as a selling tool. These images are all of the same stone. one have been retouched other than cropping. The top two were both taken through the desktop unit and the difference is in the diffuser used and the size of the black shield covering the back of the stone. The bottom row were taken through the handheld. The one on the left was from above, the one on the right from below.

What can we conclude about the stone (as opposed to about the photographer) from these images? It’s at least pretty good, that much is clear in all of them but is it a rocking super-ideal? Why or why not? Given one of these images without the explanation of how it was produced, what needs to be considered unreliable data in making a conclusion? Put another way, taken in isolation and with no details provided, would these images lead to different conclusions?

Neil Beaty
GG(GIA) ICGA (AGS) NAJA
Professional Appraisals in Denver

Neil,

4 points:

1) What do you think of the pictures that WF had produced, to document their diamonds?
2) With respect to the variation you get in your pictures, do you find that you can get:
a) a consistent "live" visual evaluation, regardless of the pictorial output
b) is one of your pictures more like your visual evaluation
3) in your 4 pictures...if you apply the rules of thumb Garry''s documented at his idealscope site...

"ASET shows where a diamond gathers its light.
Blue is blocked by the observer (some blue adds contrast)
Red is best: most light comes from above –from the ceiling
Green is OK; it is reflected and from windows, but red is better
White shows how much leakage is present (bad, especially when the leakage is adjacent to blue; when you will see a large dead dark zone in normal lighting)"

...might you find that all perhaps but your top right can be applied to the basics presented there, even though there is variation?

4) your public efforts here on presenting both the results of your work, and your documenting for us as to how you have achieved them, are much appreciated, and probably help many consumers in the long run, and other professionals such as yourself in the short run.

P.S. If #3 is close to right, perhaps the question remains as to how to not get the top right repeated. Maybe you guys can "talk amongst yourselves."

Regards,

 

[Garry H (Cut Nut)]

Date: 12/11/2006 12:01:32 PM
Author: denverappraiser

Here’s my problem with the current state of ASET photography as a selling tool. These images are all of the same stone. one have been retouched other than cropping. The top two were both taken through the desktop unit and the difference is in the diffuser used and the size of the black shield covering the back of the stone. The bottom row were taken through the handheld. The one on the left was from above, the one on the right from below.

What can we conclude about the stone (as opposed to about the photographer) from these images? It’s at least pretty good, that much is clear in all of them but is it a rocking super-ideal? Why or why not? Given one of these images without the explanation of how it was produced, what needs to be considered unreliable data in making a conclusion? Put another way, taken in isolation and with no details provided, would these images lead to different conclusions?

Neil Beaty
GG(GIA) ICGA (AGS) NAJA
Professional Appraisals in Denver

Neil the hand helds seem to have exposure issues.

You are using the ideal-light on the left? If so you have set the camera to tungsten (little round light globe symbol) and that is good.
But the image seems underexposed.
The image on the right side seems totally over exposed.

Does your camera have an option to take a central exposure rather than an average full frame exposure?
This might help.

 

[denverappraiser]

Garry,

The only difference you see in those images is one of exposure? I see much more fundamental issues at play but this explains how we seem to disagree about what makes one image more useful than another.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[Garry H (Cut Nut)]

Date: 12/11/2006 2:31:25 PM
Author: denverappraiser
Garry,

The only difference you see in those images is one of exposure? I see much more fundamental issues at play but this explains how we seem to disagree about what makes one image more useful than another.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

Neil it seems tthe stone has a slight table tilt. Is this correct?
If the stone has a table tilt then there will be differences in the results between resting a stone on its table and resting it with its pavilion centered in the ideal-light hole.

Sergey and Yuri have proven that table tilt should be ignored and that pavilion and crown anglle variatioons that become doubled when scanning such a stone should be adjusted as per "Octonus Theory"

But first I think we should get the photographic methods right so we can understand the data better.
Then we can argue about what the images show

BTW here is an article we wrote about table tilt http://www.gemology.ru/cut/english/symmetry/6.htm and it also shows a very good example of missgrading - the stone shown here was graded Good sym by GIA - but it has H&A''s symmetry. It shows why I went away from a table down photographic system

 

[denverappraiser]

Ira,

I find the top right image to be the most similar to what I see through the desktop unit. I prefer the dark background for my purposes because it can be done with both a mounted and unmounted stone and the backlit variety cannot. The one at the top left is the most similar to the DiamCalc simulation.

I”ll attach a .GEM file of the stone so y’all can know a little more about it.

I’m reasonably confident that the images shown on the WF site are taken in a nicely standardized way and are therefore useful when comparing one WF stone with another. Comparing a WF image with another of unknown, or even different, source is, IMO, of marginal value. Since the techniques for taking these pictures is proprietary (for good reasons I might add), I don’t see this situation becoming more standardized for consumers until AGS addresses it.

Garry,
I think what you’re seeing is caused by taking them image with the stone slightly off center in the tool, not a problem of the table plane not being parallel to the girdle plane. I agree that I much prefer the concept of images without the glass in the way. This obviously adds a variable that isn’t necessary. What the glass does do is force the leveling of the table plane with relation to the cone and prevents the stone from being in or out of the cone. It makes the images much more repeatable. As you point out, a few degrees of tilt can make a big difference, as can a few millimeters in any direction. For a standardized image, it must be level, centered in the tool and placed exactly at the opening of the cone. You’re photographic trays do a pretty good job of several of these issues and I use them for IS pictures but, at least the ones I have, don’t fit the footprint of the ASET. This approach doesn’t address the leveling topic and the standard approach seems to be one of trial and error.

No, my camera does not have a tungsten setting.

Neil Beaty
GG(GIA) ICGA (AGS) NAJA
Professional Appraisals in Denver

 

[Garry H (Cut Nut)]

Neil there is a little table tilt in the scan of the stone. You will need to read the link I posted above to understand what I mean.
The glass is bad not because of its interference etc - it is bad because table alignement is bad.

Pavilion alignment is most correct - it is not super easy - but it is most accurate because of table tilt like this and most stones have (a whole seperate issue).

As to the most correct info - only the image on the lower left has the correct 45 degree placement as evidenced by the red centre of the dead accurate diamcalc lighting. It matches best. Not that I think this is an issue.

Also the

 

[strmrdr]

Varing images from different suppliers is something we have delt with for years on here with the IS.
Once you have seen a few its pretty easy to tell if it a good stone or not even from different vendors.
Using either to compare 2 rounds even from the same vendor is rather a bad idea.
They either pass or they fail then you move on too other data.