A light for a gemologist

Flashlight Modding and DIY Parts
1

Hello everyone,
As I mentioned in my “present yourself” post, I am a gemologist. Gemology is the science dealing with gemstones. This includes many different kinds of minerals such as diamonds, sapphire, ruby, emerald, garnet, quartz etc. Most gemstones are appreciated for their color, diamond being an exception. Everybody knows about the red color of ruby, the blue color of sapphire, and green color of emerald. But things are not as simple as red, blue or green, in fact there is an infinite number of different hues, saturation and brightness for each kind of gemstone. See below an example with emerald:

You may have guessed that some colors are rarer, or more valuable than others. For example, a deep, intense “pigeon blood” ruby from Burma can be worth millions, while an under-saturated, light red ruby from Sri Lanka is worth pennies.
One of the jobs of a gemologist is to characterize the color of gemstones in order to assess their values, and trust me this is a real headache. The best way to characterize the color of a gemstone is to use natural sunlight or similar standard illuminants. However they are not always available, like in an indoor gem market or in an office, for example.
Most gemologists carry their own flashlights for such cases, but surprisingly most of the flashlights I have seen are low cri and with horribly high CCT. How can you evaluate the color of a gemstone with a low-CRI light, especially for red stones?

Below are some example of lights used by gemologists and gem merchants to give you an idea. Most of these lights have a cone-shaped head to focus the lights in a very small area. This is very useful to inspect the inside of a stone without any stray lights getting into your eyes, or to inspect the clarity and color of gemstone roughs than are not already cut.

Nitecore Gem
https://flashlight.nitecore.com/product/gem8

Noble flashlights, made by a family in Burma. The link contains a video that shows of the cone-shaped head works
https://joehenleyrough.com/products/noble-flashlight

These Chinese lights are very common, they usually have a warm white, cool white and UV led of dubious quality

I personally carry a Nitecore MT06MD with a high-CRI Nichia 219b 5000k with a nearly pure-white tint to reproduce natural sunlight.
But now I want something even better :slight_smile:

So, my goal here is to build my own dream flashlight for inspecting gemstones. One light to rule them all!
The light should have the following specifications:

  • 18650 batteries for extended runtime
  • E-switch
  • Ultra-high CRI emitters, such as Nichia Optisolis. I think Clemence’s MCPCB with 4 emitters very close together is great.
  • Two sets of emitters, incandescent-like 2700k and sunlight-like ~6000k
  • If there is room for it, a separate SST-10 UV 365nm emitter
  • The ability to select between the 2700k or 6000k emitters (for example, the light turns ON on the 2700k, two clicks on the button switches to 6000k and vis versa)
  • The ability to ramp the brightness
  • The ability to have both emitters ON at the same time and tint ramp between the two à la Sofirn LT1.
  • Any kind of frosted optic to remove any weird beam pattern due to the multi-emitter
  • Removable cone-shaped head that will sit above the optic in order to inspect the interior of gemstones

Regarding the flashlight body, I can have access to a lathe and design the body myself. Worst case scenario I could use a Convoy host I think.
Regarding the driver… I have absolutely no idea how this works. From what I understand I need a 2 channel driver to control the 2700k and 6000k emitters independently. 3 channels if I want to implement a UV emitter to the mix. I also have no idea how the Nichia Optisolis should be driven. I would need some advice on that. :slight_smile:
Regarding the UI… Again no idea how it works. I could learn how to code a UI myself. I know TK’s Anduril supports tint ramping, maybe I could use that. I would need advice on that as well.

I have good practical and soldiering skills, I used to mod game consoles. I really want to make this project happen, no matter the time or effort it will take. :slight_smile:
If you have any advice, ideas, or comments please feel free to let me know.

Cheers all

2

I think you need normlight cabinet.
Something like: JUST Normlicht - Color View Light Cabinets | KONICA MINOLTA
Mike

3

I need a small light I can bring with me anywhere :slight_smile:
Bringing a light cabinet to a gem market in Thailand is not very convenient.

4

So you can use any light than, no one will be accurate.

5

Sorry I am not sure why you are saying that. As I said in the first post I don’t want to use “any light”, I want to design and build my own gem light with specific requirements. :slight_smile:

Imagine a knife guy wanting to make his own knife with a particular blade shape, metal alloy, specific wood grain for the handle etc. Would you tell him he could just buy any knife instead because “they all cut stuff” and “the blade will get dull over time anyway”?

The light I want to make may seem a little bit too crazy, sure, but that is what is exciting. If it ends not not being possible, well to bad, at least I tried.

6

It’s not about blade.
We talk about viewing condition can be easily reproduced by widely available, certified equipment on any place on earth, not by barn made flashlight.
I work in print industry and accurate viewing and reproducing colours are my daily bread.
You could try gem spectrophotometer, but no idea if it gonna work for you. They are pretty portable.
Mike

7

Well, I thank you for your input, I will keep that in mind while making this light.
Beside, certified equipment are not always available, like deep in the savana in Madagascar for example.

Gem spectrophotometers are used in gem labs for very specific applications. Other that that, nobody use such instrument for buying or grading gemstones.

I just want a good, overbuilt light I made myself and I am reaching for you guys for specific advices :slight_smile:

8

I know 1 print house in Madagascar printing according to ISO. They have all equipment needed to reproduce colours correctly.
Imagine for a discussion sake, that you can print the same job in Madagascar and Uruguay and when you put one magazine against another and certified proof, you can’t tell a difference. You got my point when you talk about shining a flashlight on dusty market?
Have fun.
Mike

9

No, I didn’t get your point. I don’t want to sound rude but you don’t have any knowledge about the gemstone industry, and you have absolutely no idea how gemologists work.

Thanks I think building this light will be a fun experience :slight_smile:

10

You are right, but I know that gems like other thing in the world have colours, which should look the same, and are heavily dependent on viewing condition which in this case will be completely random. So you’ll get random colours :slight_smile:
EOT.
Mike

11

Again thanks for your valuable input, but I will disregard it, I think you are missing the point why I require ultra high CRI and specific color temperature. Also the flashlight I want to make is not JUST about High CRI or ultra-accurate colour reproduction. I is about building my own light in a specific format that suits me, with specific emitters and specific functions.
For example, the ability to switch between warm white and cool white light source to observe colour change in gemstones. Alexandrite for example is green under cool white and red under warm white. Being able to quickly switch between the two CCT is very useful to observe this phenomenon.

This forum is for sharing about building and modding light, not arguing why a light someone wants to build is useful or not.

12

For colour arguing customers I have small book. Images in that book look totally different when watched indoors and outdoors. Their jaw drop is priceless :slight_smile:
Quick example how in certain viewing condition fools you.
A and B square are the same colour.


Gl witch choosing gems :slight_smile:

13

You really are obnoxious aren’t you?
I hope you will give some advice about building the light itself in the future instead of arguing aimlessly for no apparent reason.

Oh I am choosing them real good already, don’t worry about that :heart_eyes:

14

I will be interested to see what you come up with. I personally think it will be tricky to get everything you want in one light. You might consider the Sofirn IF25 for high CRI tint ramping here. You might also look at the Wurkkos WK30 as an example of a multi emitter light that has UV. I don’t like them because you want a UV filter for the UV emitter and it is difficult to do that and not filter the other emitters. I don’t think this light fulfills what you want but it may give you some ideas for building your own.

15

Hey thanks :slight_smile:
I know those lights, I think the Sofirn IF25 is great btw, it and the Sofirn LT1 gave me the idea of making a tint-ramping gem-light.
It is not quite the format I am looking for, otherwise I would certainly have bought them, but yes it gives me ideas :slight_smile:

16

So talking about best colour rendering led it would be full spectrum Yujiled or some quality competitor if exists.
Now you need host and driver.
Mike

17

Incandescent/halogen not good enough? A bit power-hungry, but no big gaping holes in the spectrum.

No matter what “high-cri” LED you get, there’ll pretty much always be the big blue-green hole. So especially with emeralds where it’s especially critical to look at colors in the blue-green part of the spectrum, pretty much all LEDs will suck.

Even for Yuji, hailed as one of the best as car as cri, lookit the spectral response:

And find similar curves for “high-cri” LEDs, and they’ll all have that big hole in the blue-green.

18

Wow, I didn't know that Lightbender.

You learn something new everyday!

19

Thanks I will look into that.

I don’t feel confident enought to build a light with both incandescent and halogen bulb inside. Also I can’t take the risk to have the filament burn out when I am out in the savana. Also I need a rather small light, think zebralight SC sized.

Yes that is unfortunate… I spoke with Clemence and he told be the Optisolis has a relatively weak hole in the blue compared to other LEDs.
I know it won’t be 100% perfect, but I am sure it will still be better than 99% of the lights my colleagues use :slight_smile:

20

He fixed himself to led :slight_smile:
I tried to explain him earlier, but no juice.
Mike