Standardizing lighting for ideal-scope/reflector type photography

[JohnQuixote]

Greetings fellow diamophiles.

Ideal-scope photos have become common parlance on PriceScope. Soon AGS ASET - angular spectrum evaluation tool - photos will enter our lexicon of performance-assessment as well. There is an increasing need for standardization of this kind of photography. Logically, the most important and variable component is lighting. To this end we would like to share our approach, and welcome discussion on the subject.

We strongly believe diamond performance should be assessed in real-world lighting conditions. Therefore our IS images are all made with backlighting that most closely represents natural daylight: We like an image that appears the same as what we see in a hand-held IS, backlit with daylight through a window.

Correlated color temperature (CCT) is based on the color of light emitted by an incandescent source and measured in Kelvins. A standard incandescent lamp has a filament at 2700 Kelvins. 5000 Kelvins is equivalent to northern exposure midday sunlight. Therefore we use a 5000K (+/-270 CCFL) color-corrected daylight source in a controlled environment to backlight our ideal-scope photos.

Level of intensity is important but easier to control as it depends primarily on the size of the lighting environment. Simply put, if the intensity isn’t enough you lose detail and if too bright it appears to wash out. A rule of thumb for controlled photography: Once CCT and color-correcting elements with CRI near 100 are established your eyes may be the judge of appropriate intensity.

We are often asked about our methods of photography – so we are sharing our research in the interest of a common goal.

 

[JohnQuixote]

Diagram of our setup. We are using the rapid photo system tray

[ Edit: New illustration posted farther down in the thread that more accurately represents light source size/proximity ]

 

[JohnQuixote]

Photo - using this system - of a diamond cut for limited light leakage.

1.081 G VS2
60.9, 55, 34.9, 40.9

 

[JohnQuixote]

Photo - using this system - of a diamond cut for contrast.

1.064 I VS1
60.7, 56, 34.2, 40.7

 

[JohnQuixote]

Two photos of one diamond

1. In an old system (washed out look)
2. In the described system with photo tray + CCT, color-corrected, intensity adjusted lighting.

1.151 G SI1
60.8, 55, 34.9, 40.8

 

[denverappraiser]

John

You’re the man!

Doesn’t the size of the diamond make a difference? Since the aperture of the IS is fixed and the intensity of the light is fixed (?) doesn’t a bigger stone produce a different look because it fills up more of the viewing field?

What is the acronym CRI?

What camera and lens are you using? Digital cameras seem to enjoy automatically messing up the color mix and this seems like a problem.

How are you getting the alignment right so that the image is taken from a direction that is perpendicular to the table? It seems like a few degrees of variation can have a profound affect on the image.

Do you have any idea if AGS’s plans include ASET images of real stones (as compared to virtual images of models of the stones)? They have surely put some thought into this and, as you point out, it would be useful but I’ve heard no discussion of the matter.

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

 

[Garry H (Cut Nut)]

Well done John.

A couple of points though.
The light should be wider (or at least as wide) as the opening under the tray.
The should be sitting right atop the tray (yours appears seperated and is a smaller light source? more directional than flood type?)
http://www.ideal-scope.com/manuf_iscapture.asp
shows the tray sitting right atop a http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=232466&is=REGlight used for viewing Xrays and transperancy photo''s.

We see no need for the camera to sit right atop the Ideal-Scope - but have no objections to that.

 

[plg_cp]

This information is very useful, thanks John.

I have perhaps a stupid question about light and the Ideal Scope:

Assumptions: 1) with the IS, the light source is through the bottom of the stone; 2) we are viewing the stone in the IS through the table/crown; 3) a well-cut diamond has minimal light entering crown facets that leak out the pavilion

My question then is how the IS helps us to evaluate light leakage (light pink/white areas) as it is relevant to the real-world (ie where light enters through crown facets) since the IS environment doesn''t replicate this scenario?

I realize this is a convoluted wording but I''m trying to be clear.

Basically I''m wondering what the reasoning is for setting up the IS to use lighting through the pavilion instead of the table. Wouldn''t the latter allow us to see how much light is actually leaking?

I''m waiting for my IS to arrive in the mail (I''m in Canada...) otherwise I may have been able to answer my own question by trying it...

Thanks,
Mark

 

[Garry H (Cut Nut)]

Date: 4/4/2005 4:25:35 PM
Author: plg_cp
This information is very useful, thanks John.

I have perhaps a stupid question about light and the Ideal Scope:

Assumptions: 1) with the IS, the light source is through the bottom of the stone; 2) we are viewing the stone in the IS through the table/crown; 3) a well-cut diamond has minimal light entering crown facets that leak out the pavilion

My question then is how the IS helps us to evaluate light leakage (light pink/white areas) as it is relevant to the real-world (ie where light enters through crown facets) since the IS environment doesn''t replicate this scenario?

I realize this is a convoluted wording but I''m trying to be clear.

Basically I''m wondering what the reasoning is for setting up the IS to use lighting through the pavilion instead of the table. Wouldn''t the latter allow us to see how much light is actually leaking?

I''m waiting for my IS to arrive in the mail (I''m in Canada...) otherwise I may have been able to answer my own question by trying it...

Thanks,
Mark

Hi Mark,
Newtons third? law of thermo dynamics - for every action there is an equal and opposite reaction.

If light can enter the pavilion and exit the crown.
Then light can enter the crown and exit the pavilion.

this is directly proportional so the ideal-scope is a very simple way to detect leakage.

NEil you asked about AGS ASET scope.
I am sure all their plans will be made public after next weeks AGS conclave.

 

[JohnQuixote]

Date: 4/4/2005 10:57:42 AM
Author: denverappraiser




John

You’re the man!

Doesn’t the size of the diamond make a difference? Since the aperture of the IS is fixed and the intensity of the light is fixed (?) doesn’t a bigger stone produce a different look because it fills up more of the viewing field?

Thanks Neil

I thought you'd warm to this subject.

Since the color temp of the lighting is fixed the saturation is the same edge-to-edge no matter what size. The only difference we may see is that a very big diamond blocks a fraction more of the light entering the IS – but for purposes of analysis it’s negligible. This is the advantage of calibrating to CCT. When we’re talking in terms of variable intensity there is obviously a difference.

What is the acronym CRI?

CRI is Color Rendering Index. It’s a measure of the degree of color shift objects undergo when illuminated by a lamp, compared with those same objects when illuminated by a reference source of comparable CCT: It’s why color-correction is important with this process. A CRI of 100 (the highest) is similar to the sun at midday. A lower CRI will result in some colors appearing unnatural, which has an effect on the consistency of the hues observed. Most cool white fluorescent lamps have a CRI of 62

Some fluorescent lamps with phosphors are available with a better CRI. Incandescent lamps have a CRI >95.

What camera and lens are you using? Digital cameras seem to enjoy automatically messing up the color mix and this seems like a problem.

This has been a years-long project. We’re currently testing camera equipment for a major manufacturer and not at liberty to disclose details…yet. I’ll PM you with what I can discuss.

How are you getting the alignment right so that the image is taken from a direction that is perpendicular to the table? It seems like a few degrees of variation can have a profound affect on the image.

This is like the answer given by the corner musician when the young boy asked him “Sir – how do you get to Carnegie Hall?” “...Practice, son. Lots and lots of practice.”

It just plain takes time. Garry’s rapid tray system has helped, but it still takes much effort and many images to get the right shot. More man-hours than most people realize are dedicated to producing and rotating-in clarity and IS photos - as well as Sarins and grading reports. If you come up with a fast way please let us know!

My understanding about ASET: Possibly color-coded photos of actual diamonds. Have you seen the images produced by Imagem? The ASET examples I've seen look something like that but with projection of angular ranges coded by color. We'll probably be enlightened more after next week.

 

[noobie]

Awesome pics John! Having spent hours trying to take IS pics, I gave up. So I know how challenging they are.

Efforts to standardize the photos are indeed very noble. It one of the things that would help consumers compare stones. However I would add that with the super dooper stones that the vendors here sell, the IS''s usually look very comparable. I would think that all of you new line ACAs ISs would look virtually indistinguishable. Which raises another question. Can you infer the personality or characteristics of a stone through the IS. I know that the new and old line ACAs have characteristic looks, but some of the discussion here about lower girdles and minor facets; can they be judged with an IS?

I guess no one would want to try to hawk a poorly cut stone with an IS photo

 

[JohnQuixote]

Date: 4/4/2005 408 PM
Author: Garry H (Cut Nut)
Well done John.

A couple of points though.
The light should be wider (or at least as wide) as the opening under the tray.
The should be sitting right atop the tray (yours appears seperated and is a smaller light source? more directional than flood type?)
http://www.ideal-scope.com/manuf_iscapture.asp
shows the tray sitting right atop a http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=232466&is=REGlight used for viewing Xrays and transperancy photo's.

We see no need for the camera to sit right atop the Ideal-Scope - but have no objections to that.

Thank you Garry.

It’s your recipe. Now it’s up to the rest of us to set the goblets and silverware in the same places on our tables.

1. Our light is indeed wider than the tray (forgive the crudity of my drawing). It is not a directional light – it’s a flood as you suggest. I will redo the illustration.

2. With respect, we disagree with putting the tray on top of the light source. We used to do this and you told Brian our light source was too strong. We looked into the "pocket slide & film strip viewer" light provided with your system (catalog number 96MSV). According to the manufacturer it has no published Kelvin temp and is not color corrected. That doesn't work for us, since natural lighting is our priority.

More on this as regards standardization:

Any suggested intensity will be relative to environment size. "Too strong" in a small environment may be "too weak" in a larger one. Terms like "lumens, candles, footlamberts," etc. measure different aspects of light and don't necessarily relate to each other anyway.

However, Correlated Color Temperature or CCT (as long as it's color corrected) is a constant and CAN be standardized. So...Rather than hit and miss we chose to replicate natural daylight as our source and it has worked out well...'naturally'

We found that moving the diamond just an inch from the light source allows for ambiance in lighting, as it would occur in nature…You know, when using natural daylight as a backlight the sun is not sitting right atop the diamond. When allowing an inch of separation the images accurately represent what we see using a hand held ideal-scope observing the diamond with ambient natural daylight as a backlight.

3. As for the camera sitting on top of the IS – we favor that, as it reduces the risk of light coming in through the aperture of the IS and reflecting off of the crown.

 

[JohnQuixote]

Here is a 1.061 J VS2
60.5, 56, 34.8, 40.8

Too close to the light source.

 

[JohnQuixote]

Same diamond with ambient lighting (tray system & an inch further away from the source).

 

[JohnQuixote]

Date: 4/4/2005 6:26:26 PM
Author: noobie
Awesome pics John! Having spent hours trying to take IS pics, I gave up. So I know how challenging they are.

Efforts to standardize the photos are indeed very noble. It one of the things that would help consumers compare stones. However I would add that with the super dooper stones that the vendors here sell, the IS's usually look very comparable. I would think that all of you new line ACAs ISs would look virtually indistinguishable. Which raises another question. Can you infer the personality or characteristics of a stone through the IS. I know that the new and old line ACAs have characteristic looks, but some of the discussion here about lower girdles and minor facets; can they be judged with an IS?

I guess no one would want to try to hawk a poorly cut stone with an IS photo

Thanks Noob.

I’d like to see IS standardized across the board for the reasons you allude to: Most of the vendors here have it figured, but as IS and ASET gain popularity it would be nice to see a level playing field for all.

You’re right – woofers are less hawk-able with this info.

As for inferring the personality (I like to call it character) of a diamond by viewing an IS…I can tell quite a bit, especially about contrast qualities of brilliance – though having the pavilion patterning (hearts) image tells me much more.

Jonathan has made a habit of this kind of study. Maybe he will share his thoughts and Brian, myself & others can follow-up.

 

[Garry H (Cut Nut)]

It is absolutely admirable good Sir Knight, that you have devoted such attention to the color temp of the light source. But it is of hardly any relevance.

It is however more important that the light source floods the entire tray and i still imagine your source is further away from the tray than is optimal (like the Firescope siutation which is also less than desirable.

It is also worth noting that the tray system does not provide the same lighting as a free hand held stone with tweezers. But for a raft of overly technical reasons - I now prefer this ''perspex adjusted pavilion illumination'' to the hand held tweezer method.

It is a matter of time (short time, not a long time) until we will have gem Adviser files listed in the search by cut quality section of Pricescope by some vendors. This will make standardisation of ideal-scope and natural lighting photography ''standardised'' - so it would make sense that anyone taking these types of photo''s to consider the equaliztion effect of the gem adviser files.

That is why I have done all we can to provide a rapid photographic system for the taking of these photo''s.

 

[WinkHPD]

I have the small tray with the light source that Gary sells and the idealscope that I take my pictures through.

I do not have the ability to raise and lower the light source nor do I have a clue what the light temperature is. Gary do you know? (Of course you do, you make the thing..)

I do know it gets consistent pictures, if you have a good stone, you get a good pattern, if you do not, you don''t.

I am not sure we will ever be able to "order" people to use a standardized set up for taking the pictures, but there does need to be a system to prevent people from claiming the photo from one stone is not actually the photo taken from another stone. That I think presents a larger potential problem than minor differences in photo setup will ever do. (Hmm, that reads awkwardly. I do not want people to be able to take a picture of stone B and claim it belongs to stone A)

John, I think people will strive to learn to take photos like the "good" photos that you took simply because the bad ones make the good stone look bad. Are you saying that a bad stone can be made to look good only with a change of lighting? That does not seem logical to me, but I understand full well that logic and science do not always fit hand in glove.

In any case, this is an interesting issue, and one that is going to see a LOT of interest in the days and months to come.

Wink

 

[Garry H (Cut Nut)]

Wink the lighting position on our little $25 light is purr''fect.
The light is very warm - yellowish. you can compensate for it with most camera lighting settings by setting on Tungsten. Either way it is not a big problem - the difference between yellowish and pure white is intuitive for anyone to see - but the WF pure white looks more professional.

Keeping good strong batteries in the unit will help though. And one of the Cabin lightswe rcomend and tray system we sell is also a good idea. At $100 we just cover costs on the small runs involved.

 

[WinkHPD]

Please email me more information, I am running through batteries on your little light like a man with an ulcer runs through tums and rolaids...

I just got my first new princess cut from Paul, one of his AGS 1''s, (gee it''s only excellent in light performance, every thing else is ideal). I hope to have an AGS 0 here soon, but they are going to be VERY tough to make. Here is its Idealscope, you can see that I am having trouble with getting enough depth of field to keep it all looking in focus. This picture is like two minutes old...

Wink

 

[JohnQuixote]

Thanks again, M’Lord Garry.

I applaud what’s been done thus far – we’re constantly singing the photo tray’s praises - but methinks we may be looking out for your future more than you are.

AGS will standardize ASET. If IS wishes to stay abreast there should be a plan allowing a photo taken at WF and one taken at the JC Penney jewelry counter in Altoona to have the same white balance, saturation and hue. Having a prescribed CCT for ideal-scope that is repeatable will make your position stronger. You should consider it, Garry.

As for optimum distance from the tray – have another look at the two photos of the 1.061 above. I see more detail and a more natural look in the second one. Which do you prefer?

 

[Garry H (Cut Nut)]

I am not so concerned with super ideal as I am with the stones that look good on ideal-scope photo''s - but are actually not good Sir J.

I repeat, standardisation for standardisation''s sake is of no great interest to me if the results are unchanged, or any system makes bad stones look good, or good stones look bad.

 

[JohnQuixote]

Date: 4/4/2005 93:42 PM
Author: Wink

John, I think people will strive to learn to take photos like the 'good' photos that you took simply because the bad ones make the good stone look bad. Are you saying that a bad stone can be made to look good only with a change of lighting? That does not seem logical to me, but I understand full well that logic and science do not always fit hand in glove.

In any case, this is an interesting issue, and one that is going to see a LOT of interest in the days and months to come.

Wink

Ack!

No no. No one is trying to make a bad stone look good or vice versa.

We are simply promoting natural lighting for performance assessment.

Ideal-scope photos have become common parlance...Soon AGS ASET photos will enter our lexicon as well...There is an increasing need for standardization...To this end we would like to share our approach.

I do think that if we had standardization we would all learn more from comparisons, and an ideal-scope photo with CCT is repeatable - the biggest criticism of other performance assessment tools is that they are not.

 

[DiamondExpert]

One of Paul''s new PR''s (1.07ct., F, SI1) at 1000deg C...gosh, I hope doesn''t mind my little experiment!

 

[RockDoc]

I ''ve got an LED natural daylight lamp that is 5800degrees Kelvin.

I''ve the best for photography is 4700 kelvin.

So what are your recommendations, and how many different kelvin lamps has WF used, and what were the results with each?


Rockdoc

 

[JohnQuixote]

Date: 4/4/2005 10:46:23 PM
Author: DiamondExpert
One of Paul''s new PR''s (1.07ct., F, SI1) at 1000deg C...gosh, I hope doesn''t mind my little experiment!

Gary! That''s "K" not "C"!!!

LOL

 

[Rhino]

Interesting pic Wink. I was wondering how Paul's princess cuts would look. That image gives an understanding of why it didn't get ideal grade. Being a photo junkie of these sorts I have some thoughts to contribute when I get up to work.

 

[JohnQuixote]

Date: 4/4/2005 10:52:45 PM
Author: RockDoc

I ''ve got an LED natural daylight lamp that is 5800degrees Kelvin.

I''ve the best for photography is 4700 kelvin.

So what are your recommendations, and how many different kelvin lamps has WF used, and what were the results with each?

Bill,

WF has used several sources, but 5000K is the one we''ve found most favorable - equivalent to natural conditions - that''s our recommendation.

 

[Garry H (Cut Nut)]

This is why Wink''s Princess has those strong leaky patches.

However this stone will have a very good light performance through the center of the stone and the leakage areas will provide contrast because they are directly adjacent to those strong light return areas.

the ASET scope does provide additional information in terms of the direction that illumination is sampled from - it will be very difficult for first time consumers to learn - but we are looking forward to growth in the Colored reflector market.

 

[JohnQuixote]

Re-did the illustration with a more accurate representation of our light source's size/proximity.

 

[denverappraiser]

John & Garry,
Unlike the diamond dealers here, much of my interest in this topic has to do with getting a decent image on mounted stones. This prevents use of the tray system or the little light tray that you’re selling. Decent tools for analyzing and documenting the optics of mounted stones are few and far between and this seems like it has tremendous potential. It would be especially useful if it were possible to take a sufficiently standardized image that it could be overlaid or compared with a previously taken pic by someone else and have a reasonable chance of recognizing it as the same stone.
What I really want is a reasonable way to convert these images into a DiamCalc or GemCalc wireframe diagram. Standardized pictures seems like a giant step towards this. While I’m at it, I wish I were taller.

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