Lighting: Can good look bad, and bad look good?

[oldminer]

From time to time we read here that the kind and amount of lighting can fool the eye to an extent when it comes to judging diamond cut quality. Of course, in absolute terms, all diamonds are equal in a dark room, but this does not prove that all diamonds are equal under equal amounts and types of light otherwise.

Since personal taste comes into play with what "looks best" it would be very difficult to develop a means to test different cut styles in different lighting as to personal cut preference. We can discuss it, but we can''t tie it all up into a meaningful result.

One thing we can say is that poorly cut diamonds are obviously poorly cut under nearly all lighting circumstances. Low light levels give our eyes less ability to discriminate, so some poorly cut stones do look nice in candle light. Give our eyes enough light to make discrimination and fewer diamonds make it to the top of the scale of beauty.

Logic dictates that one must have enough light present to discriminate how well a diamond is cut. Having low lighting makes for poor discrimination, and does not make a poor diamond better. It can trick our eyes, but in grading diamonds it isn''t tricks we''re after, its discernible truth.

 

[strmrdr]

I am actually considering doing an article on this.

It would take more than my arm will tolerate right now to tell all my feelings on this subject so im just giving a couple examples:

Take a super-ideal diamond, take a average cut diamond identical mounting, afternoon on a sunny clear day. Back to the sun, hold mounted diamonds at arms length so they aren't in shadow and reflecting back to the eye.
Which is the better diamond? :}

Jewelery store spot lighting is another area where the bad can look good.


Where can the good look worse than the bad: some low light conditions and some off axis conditions.
For example earrings, Garry is pretty convinced that shallow pavilion diamond perform better than AGS0 diamonds under those conditions.
I agree with him for more than a few reasons.

Thats it for now :}

 

[decodelighted]

Date: 11/22/2005 3:20:39 PM
Author: strmrdr
off axis conditions.

Say whaaaa? What the heck is an "off axis" condition? (I can''t be the only one in the dark, admiring poorly cut stones in their natural habitat?

)

 

[Regular Guy]

I have no idea. I had earlier been inclined to agree with you.

This is the theory, metaphorically, of "G," as applied to intelligence...that there is one IQ, and people have more or less of it. It''s logical and appealing. But...then there is also the idea of multiple intelligences...and whether this has any bearing or not....

I had been inclined from the experts here generally, from discussions of:
a) the need to see diamonds in different kinds of lighting, to
b) the defined discussion raised by Jonathan at GOG, and
c) the implied logic of Diamond calc, to understand that it is
d) inappropriate to extrapolate that in different kinds of lighting, you get proportionately different results, where best cut shows proportionately best in good lighting, and proportionately lesser in reduced lighting (your argument)
e) and that different lighting may get different results, not consistent with a single metric, and
f) lighting situations are experienced as they are, and are completely democratic in spirit and nature, with none preferred particularly...they''re just how they are, although
g) some coal miners, etc., may need to determine they have special needs.

But I don''t know, really. Until this post, Dave, I thought that was the world accepted by most contemporary experts who look at these things. Although you have shared views sympathetic to the one you''re writing here, Dave, previously, pointing again to the idea of "G," and that there may be a "good" referent for lighting.

 

[oldminer]

Special light, like a jewelry store might have, can make a mediocre diamoind look quite nice. It can get enough dazzle from a rather poorly cut stone to make you believe that it is the one you really want. Later on, you might not be so happy. A perfect example of way more than "regular" lighting conditions creating problems for our eyes.

The off axis view is certainly another issue. Not sure about whether to put that in the light column or the angle of view column. Appearance is the end result, so there is some relationship.

Logic tells us that when a diamond is viewed in strong sunlight it may be much the same as looking at the sun itself. Our eyes become stunned by the strength of the light. This can make you think the diamond is a beauty when in truth, it is just that so much light has gone into our eyes that we don''t really see the diamond....

We know the eyes can be fooled. Magicians do this to us all the time. Machines have more potential for making records of every nuance. How much of these nuances can we possibly appreciate? How many more might exist that theoretically add value, but are somewhat beyond our natural ability to see?

 

[Regular Guy]

Dave,

Your post here has only been here 1 1/2 hours, but it does challenge much of what I think I've read, or have understood to be implied, from many here this past while. Hopefully some of these others I think I've read will take your challenge on, and if I've grasped some of the questions to address, if we take you as correct, will help answer:

- why bother to look at diamonds in different lighting conditions, since one good one will let us know how a diamond will appear, relatively, in all of them.
- is the discussion raised explicitly from GOG on indirect lighting not of any value/incorrect or challenging at best to interpret why it will be helpful as a construct
- why Diamond Calc would bother to model different lighting conditions, since one good one will suffice.

 

[squarediamondlove]

I just want to say that this post is very informative and answers the questions I raised in my previous posts. Are you saying that(aside form machines that can provide you with the details as to the cut''s qualit) given certain types of lighting our eye can only inform us of so much information about a diamond, any more will not be picked up by the naked eye. However, there are optimal lighting conditions that are more consistent form discriminating between stones.

Am I getting this right?

 

[squarediamondlove]

(I can''t be the only one in the dark, admiring poorly cut stones in their natural habitat?

)

LOL!!

 

[strmrdr]

Date: 11/22/2005 5:18:39 PM
Author: Kaleidoscopic
I just want to say that this post is very informative and answers the questions I raised in my previous posts. Are you saying that(aside form machines that can provide you with the details as to the cut''s qualit) given certain types of lighting our eye can only inform us of so much information about a diamond, any more will not be picked up by the naked eye. However, there are optimal lighting conditions that are more consistent form discriminating between stones.


Am I getting this right?

yes
I happens that one of those lighting conditions is common office lighting.
Because of the difused nature of the lighting source the symmetrical contrast and higher light return ability of a better cut diamond will be aparent to most people.
Someone who works in an office will notice the difference more than someone who works outside under the sun with no shade, given equal eyesight.
But put them under a tree outside and it changes again.

 

[squarediamondlove]

Date: 11/22/2005 5:26:35 PM

I happens that one of those lighting conditions is common office lighting.

Because of the difused nature of the lighting source the symmetrical contrast and higher light return ability of a better cut diamond will be aparent to most people.

I just though it was important how your stone looks in office lighting because that is a more common environment that diamonds are exposed to...I didn''t know that it was the optimal. I guess it makes me feel good, since it is 1 of my 2 favorate lighting conditions for my e-ring (the other being many small halogen lights).

I know you didn''t want to right to extensively on this here, but I would love to hear more about lighting conditions.

 

[Dancing Fire]

Date: 11/22/2005 5:26:35 PM
Author: strmrdr

Date: 11/22/2005 5:18:39 PM
Author: Kaleidoscopic
I just want to say that this post is very informative and answers the questions I raised in my previous posts. Are you saying that(aside form machines that can provide you with the details as to the cut''s qualit) given certain types of lighting our eye can only inform us of so much information about a diamond, any more will not be picked up by the naked eye. However, there are optimal lighting conditions that are more consistent form discriminating between stones.


Am I getting this right?

yes
I happens that one of those lighting conditions is common office lighting.
Because of the difused nature of the lighting source the symmetrical contrast and higher light return ability of a better cut diamond will be aparent to most people.
Someone who works in an office will notice the difference more than someone who works outside under the sun with no shade, given equal eyesight.
But put them under a tree outside and it changes again.

what is common office lighting?

 

[strmrdr]

common office lighting == strongly diffused bright florescent lighting, 8 foot white to off white ceiling.

 

[Garry H (Cut Nut)]

Anyone who has met me know I never go anywhere without this box with a good and bad stone.

I have NEVER found a lighting environment that makes the bad look better than the good.

 

[valeria101]

Date: 11/23/2005 12:56:19 AM
Author: Garry H (Cut Nut)

I have NEVER found a lighting environment that makes the bad look better than the good.

Well, I was going to write something along the same lines.

Why would lighting matter that much? Any of it would be subject to the same optical properties of the diamonds.

Of course every diamonds looks different in every light, but that is beyond the point.



Choosing some standard lighting conditions for cut grading or panel studies sounds like a matter of research method, not cut design

 

[strmrdr]

Date: 11/23/2005 12:56:19 AM
Author: Garry H (Cut Nut)
Anyone who has met me know I never go anywhere without this box with a good and bad stone.


I have NEVER found a lighting environment that makes the bad look better than the good.

put lots of backlighting behind both and little front lighting.

 

[valeria101]

Date: 11/23/2005 2:54:27 AM
Author: strmrdr

Date: 11/23/2005 12:56:19 AM
Author: Garry H (Cut Nut)
Anyone who has met me know I never go anywhere without this box with a good and bad stone.


I have NEVER found a lighting environment that makes the bad look better than the good.

put lots of backlighting behind both and little front lighting.

... so what does that do? Perhaps the leakage ''holes'' are plugged somewhat, but there is more to ''good cut'' than that, no?

There are no back-lit settings, btw.

If you can find where to cut the line between common-sense observation conditions and branded black-box metrics, let me know. That previous post of mine tried to dodge this issue saying ''any light is just light''. I suppose that is so once there is a definition of what constitutes desirable optical effects, and that obviously comes from observation in some natural conditions (not modelled or constructed). So the issue was just pushed back a nudge, admittedly.

 

[strmrdr]

Date: 11/23/2005 3:03:34 AM
Author: valeria101

Date: 11/23/2005 2:54:27 AM

Author: strmrdr

Date: 11/23/2005 12:56:19 AM

Author: Garry H (Cut Nut)

Anyone who has met me know I never go anywhere without this box with a good and bad stone.



I have NEVER found a lighting environment that makes the bad look better than the good.

put lots of backlighting behind both and little front lighting.

... so what does that do? Perhaps the leakage ''holes'' are plugged somewhat, but there is more to ''good cut'' than that, no?


There are no back-lit settings, btw.


If you can find where to cut the line between common-sense observation conditions and branded black-box metrics, let me know. That previous post of mine tried to dodge this issue saying ''any light is just light''. I suppose that is so once there is a definition of what constitutes desirable optical effects, and that obviously comes from observation in some natural conditions (not modelled or constructed). So the issue was just pushed back a nudge, admittedly.

well i can see an attempt to be funny failed :{

as far as backlit settings there are settings that have a stong blacklight effect.
care to guess what they are? They are common in pins pendants and earrings but less so in rings.

 

[strmrdr]

Date: 11/23/2005 1:02:01 AM
Author: valeria101

Date: 11/23/2005 12:56:19 AM

Author: Garry H (Cut Nut)


I have NEVER found a lighting environment that makes the bad look better than the good.

Well, I was going to write something along the same lines.


Why would lighting matter that much? Any of it would be subject to the same optical properties of the diamonds.


Of course every diamonds looks different in every light, but that is beyond the point.




Choosing some standard lighting conditions for cut grading or panel studies sounds like a matter of research method, not cut design

lighting/viewing conditions is the most important variable in how a diamond looks at any given moment above even cut.
Without talking lighting conditions you cant even talk diamond performance.
There are trade offs in cut that make diamonds apear better in one light than another so using one light envirement can lead to not so great overlall performing diamonds because they are not well balanced to perform in a variety of lighting conditions.

 

[Garry H (Cut Nut)]

Date: 11/23/2005 3:07:33 AM
Author: strmrdr
as far as backlit settings there are settings that have a stong blacklight effect.
care to guess what they are? They are common in pins pendants and earrings but less so in rings.

Worn on one of these glowing beuaties?
http://www.handbag.com/graphics/library4/sharonstonecannes1.jpg

 

[valeria101]

Argh... my sense of humor

About pins and pendants... well, they get ''pinned'' against a dark background too. So even if there is some light from the back as this setting may allow, for example, it can only be a feeble transmitted bit of the frontlight. Some dangling earrings get suspended mid air and those could conceivably get light sources from the back - but that is about all I can think of.

I am not sure back lighting (as much as it makes it in front anyway) makes any contribution to contrast and fire, and this is why I have some doubts that even carefully constructed lighting can make those two extreme examples in Garry''s picture sing along

 

[valeria101]

Date: 11/23/2005 3:20:08 AM
Author: Garry H (Cut Nut)

Date: 11/23/2005 3:07:33 AM
Author: strmrdr
as far as backlit settings there are settings that have a stong blacklight effect.
care to guess what they are? They are common in pins pendants and earrings but less so in rings.

Worn on one of these glowing beuaties?
http://www.handbag.com/graphics/library4/sharonstonecannes1.jpg

Gee... I expected some deep sea bright jelly!

... not that ladies don''t outsparkle diamonds all the time

No bioluminescence required.

 

[Regular Guy]

Well, I for one find the direction of this discussion pretty appealing. Previously, when a poster indicated he was confused about all this talk about the variance of differing lighting environments, I said I was too, from reading here, and offered a tissue.

Clearly what's being missed is the effect, however, of obscuration in an office environment. In a more standard environment, large objects don't get in the way, and the light performance can be judged on its own. But in an office environment, you have the obscuring effects of PCs, that dominate today's offices. Sometimes you are in an older office, in which case they are not PCs but Olivettiis and Underwoods. In not so old offices, they are perhaps selectrics, but typewriters all. In the newer offices, they are PCs, and they obscure the light being reflected on diamonds, causing the unusual optical effects we see.

Sorry, couldn't help myself. I would have said, and could say, that the different comments offered of late on the value of contemplating the effects of the lighting environment can be associated with the philosophical differences between direct observation, and indirect observation...that with indirect observation technology, and methods of ray tracing, etc., the only evidence to point to is that produced by theoretical models of how light behavior should work, and so the construct becomes very important to account for the predictability of light behavior. Alternately, with direct methods of observation, you can go more to simple cause & effect...and so...if you see confounding performance consistently in certain environments, you could but needn't go to a theoretical model. Instead, you can simply avoid those options that don't perform well in some supposed environments, whether or not their proportions conform to those of a certain type. Anyway, I was thinking I'd try to find an association of some sort between those proponents of indirect observation aligning with the irrelevance of lighting environments, and those proponents of direct observation aligning with the value of considering things like the effect of indirect lighting. Specifically, I went to the GOG site to learn more about this, and my own theory about this failed. Forgive me for laying my own constructs on what others think. Let me go about shooting myself down, and this may or may not serve Dave's original post. Objections to Dave's implicit idea here (and perhaps the principles of simple physics theory) as I saw them were, as noted above:

Date: 11/22/2005 4:58:05 PM
Author: Regular Guy

- why bother to look at diamonds in different lighting conditions, since one good one will let us know how a diamond will appear, relatively, in all of them.
- is the discussion raised explicitly from GOG on indirect lighting not of any value/incorrect or challenging at best to interpret why it will be helpful as a construct
- why Diamond Calc would bother to model different lighting conditions, since one good one will suffice.

Regarding the first point above, although Wink comes to mind, lots of people on this board do talk about the importance of seeing diamonds in all kinds of environments to evaluate them properly. Although you may want to get a diamond out of the showcase to evaluate it without all those lights...maybe at least if you left them there, you could at least evaluate them proportionately to the others in the showcase, and that would be fine, and the relative comparison, between all those together in those bright lights, would at least be accurate...inasmuch as you're comparing diamonds at the same shop, at least.

To the second point...I did go to Jonathan's site. He does actually discuss this some. Frankly, he even discusses head obscuration with respect to brightness, and I wasn't able to get it, inasmuch as it was supposed to be associated with indirect light; maybe he will come here and explain further. There's no quarrel about his discussion of optical symmetry. But, I'll copy below his text about scintillation:

"In direct light conditions the amount of fire and scintillation observed is dependant upon how much light is primarily being directed at high and medium angles (high angles are from 76° to 90° (observer head), medium angles are from 45° to 75° and low angles are from 0° to 44°)1. We can observe this phenomenon in our LightScope technology which shows us plainly the blacks, and contrast between dark and pale reds. Blacks and dark reds representing the high and medium angles.

In softer light conditions light being reflected at the lower angles (0° to 44° or light reds in LightScope) plays a more prominent role and doesn’t affect the reduction in light return as much in these conditions because in softer light conditions we are primarily observing more so the element of reflective/non-reflective surfaces."

OK, so I presented it as I saw it, but I'm still not really getting it. But, he does try to develop the argument. Not meaning to carry his water. Maybe others will see here what I'm missing. I'd really like to understand the point.

Now, on to DiamondCalc. Garry and others can probably answer. Why oh why do all the analysis of different lighting environments, if relatively, they don't' matter that much. (eta) I did go the tutorial associated with DC, to even look for helpful ties to this topic. Although a considerable amount is written about the mathematical correlates we can associate with perception, I saw no intended direct tie in to the application of this information to varying lighting environments.

I'm not sure if I've put stresses on Dave's post, trying to shake it at its central core as I read it...in helpful ways. I've tried to ask the questions that I think are important about it....because....quite frankly, I think that if we can understand that all well cut diamonds perform proportionately well in all the environments they perform in, such that a good test in one well represented environment should mostly suffice for putting it through a "stress test" in most any environment, this notion that the specific environment is fairly irrelevant is certainly attractive to me. I'll bet that would be true of others too.

Hoping this will be explicated further, and thanks for your indulgence.

 

[oldminer]

The work I have been part of indicates that one can pretty much discern a well performing diamond in one proper lighting environment if one is using a machine which has a high degree of discrimination and measuring ability. This is very different than what our eyes are capable of doing. Our eyes like to see objects in various lighting environments so that portions of what are visible are more well defined by certain limited lighting conditions.

The reason the various devices that calculate light behavior model light in different environments is becuase that software was developed on the way to understanding how diamonds work and how to design new cuts. They were experimenting and testing how light levels and types interact with various cuts. Does it mean a whole lot? Some will defend it and others may come to say that one lighting model can grade diamonds for cut.

We might want to argue on the "one" model that ought to be used, but one seems sufficient to make discrimination so long as a accurate measuring machine and not the eyes are used to measure performance.

Diamonds do look different to us in different lighting. Garry''s fine example demonstrates that a bad stone NEVER looks better than a good one regardless of the light and I am sure Garry has looked at those sparklers more than a few times to test out his theory.

 

[Regular Guy]

Good morning, Dave.

Apologies to mis-read your last post. The hope is that you'll stay with one argument, rather than either saying:

physics is physics, except if you believe differing lighting environments are substantive, than I have a solution for that, too...

or even just go slowly for me, from a to b to C, not from an argument about the principles of light (a), to (c), why a versatile machine can read for lots of effects.

Either let's get to (b), and why people do talk about lighting environments, and why it would matter to a shopper, or should be irrelevant to them,

Or if I'm missing your skipped step, help me out.

(edited to add): no one seems to argue about the relative effects of different lighting environments...diamonds look different in different environments, yes, we all agree. The argument I thought your post raises, and I would like to see addressed head on is this:

I think you say that for all lighting environments, well cut (or poorly cut) diamonds perform proportionately well. Is this so?

Or, in different lighting environments, do different sets of proportions perform better?

Sometimes Garry will talk about subtle differences when different shirts are put on, etc. Who cares, if the shirt color becomes relatively irrelevant for all diamonds.

I hope that we won't need pink shirt diamonds. My concern has been, however, that we may...if you want to track back that sort of thing.

Regards,

 

[strmrdr]

Date: 11/23/2005 3:20:08 AM
Author: Garry H (Cut Nut)

Date: 11/23/2005 3:07:33 AM

Author: strmrdr

as far as backlit settings there are settings that have a stong blacklight effect.

care to guess what they are? They are common in pins pendants and earrings but less so in rings.

Worn on one of these glowing beuaties?

http://www.handbag.com/graphics/library4/sharonstonecannes1.jpg

lol im shocked you didnt know what the setting is.

A properly designed buttercup setting is a parabolic reflector under the stone.
Thats why the long prongs to put the stone at the focal point of the reflector.

 

[strmrdr]

Date: 11/23/2005 7:32:05 AM
Author: oldminer
The work I have been part of indicates that one can pretty much discern a well performing diamond in one proper lighting environment if one is using a machine which has a high degree of discrimination and measuring ability. This is very different than what our eyes are capable of doing. Our eyes like to see objects in various lighting environments so that portions of what are visible are more well defined by certain limited lighting conditions.

"pretty much" ?
Im on record as saying there is no way your going to measure direct light performance of a diamond in one lighting envirement.
Just looking at diamonds accross a wide variety of lighting conditions will show that.

once imagem releases the specs of the lighting envirement I will tune a cut for that light envirement that will prove the point that one envirment can not be used to accuratly predict the light performance of a diamond accross a wide range of lighting.

Woops forgot it will be cold day in hades before they release that info.
wonder why?

You can say this diamond under this conditions has simular charactoristics to a diamond that performs well under this other light condition but you can NOT say the diamond in question would perform the same in the other lighting envirement.

 

[strmrdr]

Date: 11/23/2005 8:03:51 AM
Author: Regular Guy



I think you say that for all lighting environments, well cut (or poorly cut) diamonds perform proportionately well. Is this so?



Or, in different lighting environments, do different sets of proportions perform better?

good question :}
waiting for Dave''s answer :}

iv got a run down on another lighting envirement ready to post but going to wait for Dave''s answer.

 

[oldminer]

"I think you say that for all lighting environments, well cut (or poorly cut) diamonds perform proportionately well. Is this so?"

"Or, in different lighting environments, do different sets of proportions perform better?"

I said nothing about a direct proportionality. Garry''s example is a very good one. A poorly cut stone never exceeds the beauty of a well cut stone regardless of lighting. In the dark or nearly dark, the poor stone and the fine stone may both look about the same to many people. This means nothing.


Strmrdr knows that different lighting conditions do make some diamonds appear better or worse. I think that using standard cutting styles, a finely cut diamond should always look as good as or better than a less well cut stone. There might be some weird exception someone has in mind, but nothing comes to my mind about such a situation.

One must remember that a proper scientific "normal" lighting environment is one where the lighting employed, and the strategy used to measure performance, fit well with recorded statistics of human derived perception. If oen can measure just a few variables in a fixed environment and get a very high coorelation to actual human perception, then one is well on the way to success in this endeavor.


Someday, some person may invent a diamond specifically cut to look very special in low light. Why they would do that is beyond me and it would be one of those unusual situations that technology won''t address becfuase there would be no payback for R&D. For the vast majority of merchandise, regular lighting prevails and the best cuts are shown to be within certain ranges. Its a no brainer, but fun to discuss.

 

[Serg]

re:I said nothing about a direct proportionality. Garry''s example is a very good one. A poorly cut stone never exceeds the beauty of a well cut stone regardless of lighting. In the dark or nearly dark, the poor stone and the fine stone may both look about the same to many people. This means nothing.

Dave,

I am disagree. Your statement is not correct. Garry statement is correct.

Garry: "I have NEVER found a lighting environment that makes the bad look better than the good."

I can create light scheme for Garry example and bad stone will better than good.

The difference between your statement and Garry is very important, like difference between usual light and structure light.

 

[valeria101]

Date: 11/23/2005 10:07:49 AM
Author: Serg


... difference between usual light and structure light.

Thank you!

What is good for technical measurement (Imagem & all) does not have to be nice... And abstract models could look weird indeed if only feasible in a virtual model.

Why is there confusion between these?