I Lowered Duv with a custom paint!

So I have learned a lot of things about light from playing with my spectrometer and reading online. I decided to try an idea I had for a custom coating to lower Duv by precise amounts. And my experiments went great. So I stepped it up and did an actual flashlight.
Shown below is an old flashlight my daughter uses at night. The problem is it has a CCT of 12400! Ouch. So I added some standard CCT correction film. But that left the Duv at 0.007. So I made a Duv correction coating with precisely the right correction factor. And voila, CCT = 5089 and Duv =0.0000! And the other metrics improved too! Booya!

CCT: 12400
Duv: –0.0051
CRI: 83.0
TLCI: 58

CCT: 5089
Duv: 0.0000
CRI: 84.4
TLCI: 68

What light? What coating? Are you sure she wasn’t just using a blue light?

It’s just a free flashlight I got at work many years ago. It doesn’t have a make or model. She is only 2 years old, so I gave her that one because it can’t damage her eyes. It is indeed a white light LED. The Duv control coating is a cocktail of my own creation.

So what I am wondering now is if there is interest in me making batches of this to sell?

For example, one coat could lower Duv by a 0.002, and you just keep adding coats until you get the rosy tint you like.


It sounds great! How does one apply the coat? Does the coat change properties after some time? How does it tolerate high temperatures? What are the cd and lm drop?

I’m glad there’s a little interest, I was having fun doing this. How does loading it in a spray can sound? Everyone knows how to use spray paint. You would just spray it on the back of the lens, and re-assemble.

No, am quite confident it will not change properties over time. As far as high temps, it should survive any temp an LED can survive. I will test. cd and lumen drop are expected to be near zero, since a coating does not create any new surfaces, and the Duv change is small. I will do that now that I plan to continue.

I’m so confused. So some undisclosed coating lowered the duv of an undisclosed LED for a day and based on that you’re convinced it will perform the same with all LEDs and want to sell it? And you figure it won’t affect output at all?

None of this makes sense to me.

I really don’t have all the answers, I am reverse engineering my sloppy trial right now. I do expect losses to be small once I apply it direct to a lens. I haven’t done that yet. Hang in there. I will explain more once I am done. I don’t want to say one thing, then do another, and need to say something else.

This is interesting. It sounds like you’ve only just begun to test. I’d like to see the results of more testing, obviously. And I wonder what the effect would be from using it without the other CCT filter.

Sounds cool. Is the idea basically to paint lenses with something like translucent pink watercolor?

I finally got the Lee filter swatches I ordered, and the minus-green sheets are pretty awesome. I don’t know what kind of dye they use, but it could probably be mixed with paint thinner instead of plastic, to be used as a coating instead of a sheet.

Yea minus green filters work good. But since they are a fixed value, you have to accept the full heat they generate. Too much correction means too much heat. They generate heat in working, and from light glaring off the extra front and back surfaces. With a spray on coating, you eliminate the 2 additional surfaces, and only apply just enough correction.

Of course. If I use a filter which eats 28% of the lumens, that means 28% of the light gets converted into heat and it could potentially get too hot on very bright modes. But it sure does look nice.

That was for a “half minus green” filter. I also tried quarter and eighth, and they helped, but they didn’t really seem strong enough. So I’ll probably go with the strongest one and just be careful not to use turbo much since these aren’t in the “HT” high-temperature part of Lee’s catalog. It passed regular standardized testing for flammability and stability, but didn’t get the extra HT rating. So if I’m reading the info correctly, that means they should be fine up to at least 125 C, at which point they start to soften, and shouldn’t actually melt until 300 C. They should at least be pretty flameproof though, and retain their optical properties over time. And being squished under glass should help give it a way to shed heat if necessary.

Mostly though, back to the original topic, I was wondering what kind of dye you found to dilute and paint on.


My God my day has been stressful. NM that.

Anyway, Good news! I got the dye thing sorted, made a spray can, and got exactly the results I predicted!

So first some background. I have a lot of fun designing and making things such as a 3D printed trolling motor, a Dewalt drill powered lathe, etc, etc… And I plan to start a YouTube channel to feature those projects soon… And I know how important the thumbnail is to a video on YT, so I came up with an idea to make them stand out… I decided (many months ago) to create a signature paint to make my projects unique and look great. And I did that. For that reason I have a shelf full of base ingredients for paint making.
Then after getting this spectrometer, I got the idea to create a tinted paint that would fix the green Duv in flashlights that so many people seem to hate. It works just like a ‘minus green’ studio light filter. It’s based on deep dye, just the same. But what’s different is you can apply it direct to lenses so it sheds heat and doesn’t melt, and avoids adding new surfaces that add glare. And this way you have full control over the strength of the effect too.
I was going to call it Rosy Duv, but I was concerned that would encourage over-application and over-heating. So I’m calling it Green Delete.
One coat lowers Duv by 0.0020 and only causes 6.7% brightness loss! I’m quite happy with that. Oh, and it causes significant gains to the CRI R9 and some gains to the total CRI :smiley:
Download the test data here and see for yourself.

When can we expect this to be offered?

This could be aeesome but do some testing first, just to be sure about not peeling off under 2-3h load each day.

At the moment I’m just waiting for the coat on my FW3A to cure for a full 24 hours, then I will pop in a fully charged battery and turbo the heck out of it. If it survives, I’m game for making more.

Rock On!!

Yea, it’s an in-efficient process either way. That’s the point of the project, having the control to not add more correction that absolutely necessary. If you like rosy, you must buy rosy LEDs to start with. But if you have some with a green tint, this is a great way to adjust that out.

Alright, so I just got done turbo-ing the heck out of the FW3A with the coating on. The body got so hot I had to move my grip away from the head. But the coating shows no signs of being affected. I reversed the lens (this time with the coating behind, like it should be) and repeated. Still no signs of any change to the coating.