Please take my poll!!

[yssie]

I haven't used one yet, but I've thought about it for a while. The problem is that they aren't cheap. You could get a few necklaces instead. If you just wear pearls or make jewelry, I don't think it's worth it. But if you sell loose pearls with pictures and videos, it could help give a consistent unit measurement instead of traditional human inspection. Based on this poll, we can be sure that people will have different visual judgments when inspecting images. This poll also applies when qualifying pearls, which can give inconsistent qualifications. These machines are pretty simple. The luminance meter measures the amount of light that falls and reflects on a surfuce whitin a space in lumens. Based on that, it's easy to give customers a comparison percentage. Most of the time, these machines are used in photos or screens, but it's funny that no one thought to use them in pearls.



Yes, creating topics is an art form and it requires some work, which is why I visit this forum, but you took it to another level by incorporating other sources. I have yet to see an influencer who can pique people's interest with words rather than a pearls image or a model wearing pearls.

So this is interesting.


I've never used a light meter of any sort so tried to find out a bit more. Recognized this vendor from some of the stuff I've been reading.

https://sensing.konicaminolta.us/us/blog/luminance-vs-illuminance/

• A luminance meter measures the amount of emitted or reflected light from a surface.
• An illuminance meter (lux meter) measures photometric brightness falling upon a surface.

I'm guilty, I totally mudge up all of these words - luminance, illuminance, brightness, lightness. Oops. Anyway. Pretty clearly we'd want a luminance meter just as you said.

LS-160: https://sensing.konicaminolta.us/us/products/ls-160-luminance-meter/
LS-160 user manual: https://sensing.konicaminolta.us/wp-content/uploads/cs-ls-150-160_instruction_eng-ci1x49mk85.pdf

From the specs on Pg 110:



So if you stick a macro filter on the front of this thing it can read from a 0.4mm measurement area. That's tiny!! More than small enough for pearly uses!!

A question though. This might be me being an ignorumpus. Output is in cd/m^3. Customers are probably going to think #MoreCandelasMustBeBetter because #LightGood. Would you end up stuck trying to explain that human eyes will interpret the exact same luminance deltas as higher-contrast when the surface is darker because they actually register the cube root of physical intensity and OMG what are you talking about...? Or does calibrating the device transform readings into a colour space that better represents how we actually see? The spectral responsivity = CIE XYZ colour matching function line makes me think maybe you'd have to get additional conversion software to avoid having really confused customers

I've definitely seen pearls modelled as both light sinks and light sources - the source being all the energy that's transmitted into the nacre. Whether it bounces off the nucleus or enters the nucleus and exits later - either way it's contributing to pearls-being-lit-from-within at the expense of surface reflection intensity.

Assuming the same absorption - I guess I should actually say assuming the same conchiolin pigmentation through all nacre layers - higher nacre quality pretty much always means "more evenly-sized and evenly-shaped thin tablets packed together tight and orderly into lots of thin layers of nacre". All of which contributes to a more glossy surface with higher reflectance. So... If given a choice, would most people prefer a less lit-from-within pearl that's more sharply reflective, or the opposite? (How dramatic would the difference have to be to be seen - how much of that nuance is even perceptible to our vision)?

I don't know!!

 

[yssie]

@yssie - wow! What a triumph - you should feel so proud and happy to have teased out this dense topic in such an approachable way. I find it transformative! The biological part, which I know is beyond your interest, also plays a role (lenses, light capture, and changes that happen over time and or with disease processes) but that is individual and varies. This does not and I’m thrilled to have the take always from each of your questions. Now I have to get reading your source materials.

Thank you. This is tremendous!

Definitely. On the biological part being super important and less predictable.


TBH I feel a bit jilted by #Biology as a field at the moment

I spent months - literally months - chasing a different obsession. Why some akoya have hammered surfaces. Why it's only ever akoya, not SS or Tahitians. Why those hammered akoya are usually more lustrous than their smooth-skinned counterparts. So I'm up a seriously-out-of-my-lane genetics tree, but I've got my bootstraps pulled nice and tight and I'm trying to puzzle through because I'm confident there will eventually be an esoteric and satisfyingly comprehensive answer...

And then I asked Takahashi, and Yy said that they've actually tracked this, and whilst it's super rare it has been seen in pearls other than akoya (but yeah, mostly in akoya) and their best guess is that it's related to the nacre tightening process.

Such a simple explanation. Made so much sense. Addressed all my questions including why I wasn't getting anywhere with the gene wanderlust. And yet so totally disappointingly anticlimactic.

 

[Starstruck8]

Some preliminary thoughts:

But that's really only half the story. Iridescence create an incredible amount of contrast and body colour be d*mned. I have a feeling that when it's a question of iridescence vs. less iridescence, "more iridescent" ALWAYS wins no matter what the body colour.

I hadn't noticed this. The iridescence I've seen in pearls other than Tahitians has been pretty subtle. (Granted, I've never looked at top quality akoyas IRL.) Maybe the iridescence isn't creating the contrast, rather, it's only pearls that are good in other ways that have strong iridescence. This is not implausible - on the optics, strong iridescence is a sign of regular, evenly spaced layering.

Pretty clearly we'd want a luminance meter just as you said.
[...]
So if you stick a macro filter on the front of this thing it can read from a 0.4mm measurement area. That's tiny!! More than small enough for pearly uses!!

If you had such a meter, which parts of the pearl would you point it at? Using a meter, as opposed to a bodgied-up camera and editor, would give a calibrated, physically meaningful result. But you would still have to decide on the lighting setup and on which parts of the pearl to compare. And yes, you would still have to relate the physical measurements to what you see.

An issue I mentioned on the other thread: If you think that bright, sharp specular reflections are good, and that high contrast is good, then a perfect mirror (a "ball-bearing") would be ideal. Indeed, some top end akoyas I've seen in pictures do look pretty ball-bearing-y. But would a perfect "ball-bearing" really be ideal? Or would you want a small amount of edge blurring and leakage.

To me, mirrors and ball-bearings don't look bright. My (totally amateur) theory about this is that some part of our visual system recognizes them as mirrors, so we (correctly) attribute the brightness of the highlights to the source lighting, not to the object. But if the reflections are blurred, this doesn't happen, and we (wrongly) attribute the brightness to the object.

I spent months - literally months - chasing a different obsession. Why some akoya have hammered surfaces. Why it's only ever akoya, not SS or Tahitians. Why those hammered akoya are usually more lustrous than their smooth-skinned counterparts. So I'm up a seriously-out-of-my-lane genetics tree, but I've got my bootstraps pulled nice and tight and I'm trying to puzzle through because I'm confident there will eventually be an esoteric and satisfyingly comprehensive answer...

And then I asked Takahashi, and Yy said that they've actually tracked this, and whilst it's super rare it has been seen in pearls other than akoya (but yeah, mostly in akoya) and their best guess is that it's related to the nacre tightening process.

Yes, but why do some akoyas get the hammered look, but not others? How exactly does the nacre tightening treatment cause the hammered look (if indeed it does)? There are plenty of side tunnels in that rabbit warren…

 

[yssie]

Some preliminary thoughts:


I hadn't noticed this. The iridescence I've seen in pearls other than Tahitians has been pretty subtle. (Granted, I've never looked at top quality akoyas IRL.) Maybe the iridescence isn't creating the contrast, rather, it's only pearls that are good in other ways that have strong iridescence. This is not implausible - on the optics, strong iridescence is a sign of regular, evenly spaced layering.

I think you're right that they do *largely* go hand in hand. Like, you're not going to find extremes of super high quality re. the one characteristic juxtaposed with super low quality re. the other. But I've got pearls that are really glossy, but that show less iridescence than other less-glossy pearls. They're still all "baseline nice", I'd say... But it was an unexpected discovery. From what I've seen, though, more iridescence always always always always corresponds with more contrast, so I do think there's a causal relationship there...

I posted these in another thread here but I can't find it. Left is more glossy, right is more iridescent and more contrasty. Everyone IRL prefers tighty righty.

If you had such a meter, which parts of the pearl would you point it at? Using a meter, as opposed to a bodgied-up camera and editor, would give a calibrated, physically meaningful result. But you would still have to decide on the lighting setup and on which parts of the pearl to compare. And yes, you would still have to relate the physical measurements to what you see.

A chessboard LOL!! My hypothetical office will give all visitors the vapours

An issue I mentioned on the other thread: If you think that bright, sharp specular reflections are good, and that high contrast is good, then a perfect mirror (a "ball-bearing") would be ideal. Indeed, some top end akoyas I've seen in pictures do look pretty ball-bearing-y. But would a perfect "ball-bearing" really be ideal? Or would you want a small amount of edge blurring and leakage.

To me, mirrors and ball-bearings don't look bright. My (totally amateur) theory about this is that some part of our visual system recognizes them as mirrors, so we (correctly) attribute the brightness of the highlights to the source lighting, not to the object. But if the reflections are blurred, this doesn't happen, and we (wrongly) attribute the brightness to the object.

I was actually thinking when I wrote that that it's fortunate I'm spared from having to choose between glowballs and mirrorballs, thanks to aragonite having quite low reflectance in the grand scheme of things I think your theory has merit. With a mirror our eyes easily identify ambient light as ambient light. And I saw lots of references to the idea that glossy surfaces look "darker" to most people.

Yes, but why do some akoyas get the hammered look, but not others? How exactly does the nacre tightening treatment cause the hammered look (if indeed it does)? There are plenty of side tunnels in that rabbit warren…

The trouble is that finding out what "nacre tightening" means seems to be a non-starter, noone will publicise any processes I did read somewhere that alternating between heat and cooling was a common nacre treatment method once upon a time, so of course I tried torturing some spare freshies with ice and boiling water to make them crinkle... Not a wrinkle to be seen. Which, well, also "of course", it wasn't ever going to be that easy