Luminus SST-20-W 4000 K CRI95 color and output test

Hmmm… i don’t understand that either…

Sometimes it does, sometimes it doesn’t. Usually not any meaningful amount in either direction if the emitters are similar WRT CRI to begin with.

what is WRT ?

Maybe your spectrum has a lot of blue and a lot of red but a hole in the middle?

I think, it does make sense, since a spectrum, which exactly matches a black body radiation is considered as 100 CRI.

(For now, let’s assume, that a given spectrum is perfect for a given color temperature - we don’t want to mess with correlated color temperature /which is calculated for suboptimal light sources with uneven spectrum/)

Once the tint goes above or below black body line, it is not an accurate black body radiation anymore - so it cannot be 100 CRI in any circumstances.

The reason why many people tends to prefer ‘under BBL’ tints, that it gives more saturation to the scene.

Please correct me, if I know/remember it wrong, but the latest LED tests now work with two summarizing value instead of single CRI (Ra).

The first one is R-fidelity (Rf) - which would mean the accuracy of the color rendering - which can be max. 100.
The second one is R-gamut (Rg), which actually can be more than 100.

If above 100, we speak of adding saturation to the scene (this is when ‘under BBL’ tints), as we get more light for the parts of the spectrum, where human eye is less sensitive, thus color perception gets boosted somewhat (as a ‘side effect’, tint becomes rosy) - this effect can be regarded as pleasant and can be felt as a ‘superior’ light source - making the CRI/Rf drop seem to be of no sense, despite the measurements.

If under 100, we speak of desaturating the scene (when using ‘above BBL’ tints), where we tend to miss blue and red colors from the scene, and we talk about a tint being ‘greenish’ in most of the cases - these tints sometimes can be felt less useful/’inferior’ even with relatively high CRI/Rf readings.

Look at any measurement, which is recently provided by maukka. You can see a graph on the right with Rf and Rg coordinates. You can see a triangular area, which has white background (or another with lighter gray) - this shows, that how much under/oversaturation (difference to 100 on the Rg axis) is possible for a given value on the Rf axis - of course, less under/oversaturation is tolerated, if one would go for a higher Rf value.

Now I hope, this makes sense to you :slight_smile:

This is why I love that red dot in that graph (and the 99 color samples as well, but for a different reason).

Im going to try and mix 2x Luxeon MZ 3000K and 2x 5700K so i hope these results are similar. Someone should start a color mixing thread (maukka)

Here is why the CRI drops when mixing different LED tints.

The 100% curves for the CRI are taken from the perfect black-body radiation at different (color) temperatures. Each curve has a different maximum point and slightly different shape. 5000 K has its maximum at 580 nm and 2700 K at 1070 nm.

(Discaimer: The CRI uses black-body curves only for a CCT below 5000 K. The ‘Illuminant D’ data used for higher CCTs are too ugly to show here.)

After standardizing the curves (divide all values by the maximum value, so maximum is always 1; easier to compare) and zooming into the area of visible light you get this:

For each wavelength your LED has to get near the curve to get a good calculated CRI value. (These curves are the blue ones in maukka’s diagrams.)

The curves look relatively similar to each other, just shifted left and right so each shows a different part of itself in the visible light range.

Now lets mix a high CRI 2700 K and a 5700 K LED.
Their spectra almost fit the 2700 K and the 5700 K curve. You mix their tints by summing up the values of the two curves for each wavelength. For the same power output on both LEDs that is the dashed line.

If you make one LED brighter and the other one dimmer the curve will only change slightly. Only the maximum and the slope will get closer to the curve of the stronger LED.
See the dotted 0.4/0.6 and the slash-dotted 0.8/0.2 curves for some mixtures. The slash-dotted line would not be too bad for 3500 K but with too much blue.
I could not mimic the shape and position of the 4200 K curve.

The more the mixed tint gets away from one LED tint the worse the mixture gets. Without a curve similar to the 100% CRI curve the calculated CRI value will be bad.
To really change the color temperature of an LED you would have to shift the wavelength, not just modify the amplitude.

The penalty in CRI will be lower with less distance between the tint of the LEDs.

Thanks TBone, great explanation!

Nice post Tbone!

0K, is this tint mixing sheesh serious? LoL! On top of this, now it seems like the way we perceive light is not that close, with people boasting more than 3 types of cone cells besides rods lmao:

I have quads with high CRI 5500K + 4500K + 4000K + 3000K emitters, guess this should be working around right (without spoiling the CRI too much lol). :-D

Cheers ^:)

Also pretty interesting read on the topic of shifting tint:

Interesting. I wonder if that’s why Zanflare T1 includes red LEDs?…and if this technique can benefit BLF lantern. :wink:

I think I might have messed up my first sst-20 build with this LED. Built an E2L triple w/ FET driver. 20 gauge wires to LED and spring bypass. Worked fine when i was testing using 10A Sanyo then i topped up a Samsung 25S which is the highest drain battery i have and now all modes noticably more yellow. I measured around 2,470lm at 0s just before this happened. On moon mode the emitters are still evenly lit but still yellow.

Not sure if bad reflow or over current.

Anyone else try DD triple with these?

Don’t have a triple, but just put one in a D25c with a fet driver. No yellow yet, it does have a tiny bit of green when comparing to other lights on a white wall.

Djozz and maukka both had one die around 7A. Aren’t you worried or do you have higher resistance from bat or springs?

Edit: just noticed thats a 16340 host so that should be pretty safe

16340 cell, no spring bypass, not to thick wires. Wont be doing 7 amps, probably max 5. But indeed not a light to lend out to muggles.

Played with it for a few hours last night. Pretty nice, like it better than the 219b sw40 that was in my light before the sst.

Why do you like it more than the 219b? Is it a 9080 or 9050?

It was a 9080. I am strange I think… I find the sw40 a bit boring to be honest. And the second sw45 to cold/violet.

Y’all are really doing great with all this tint mixing thang! :slight_smile:

I’ve been looking at doing some mixing in a light I’m building that will have 17 emitters. 4 quads under Ledil Angie optics and a central single die under a 22mm reflector. I’m planning to use a sliced and sealed SST-40 in the center, originally planned 16 Samsung LH351D at 80 CRI 5000K for the quads. But I’ve been considering doing some mixing on these 4 quad boards. I have a lot of emitters to choose from, can even do a quad with 4 Black Flats and one with 4 Nichia 219C at 5000K, then maybe XP-L HD or HI or a mix of both. But I have so many options I don’t know what to do… could y’all help me figure this out?

Here’s a list of emitters I have available, the majority new and in tape, a few on boards as indicated…

The layout is like this, with the center (marked as HI) probably not being an HI but I’m still open to options.

So, would there be a viable combination in this slew of bare emitters or is it time to order something new?

This is a 4” diameter head mated to a Sofirn Q8. The center 25mm Maxtoch MCPCB is run from the original driver flashed with Anduril, there are 4 slave boards each with an FET+1 set-up that will run the 4 quad Noctigons (D4S, with Angie optics) So each quad can have different emitters, Vf differences won’t matter as the board will have it’s own FET+1 supply, with all 5 drivers being controlled by the same Anduril UI. I started out wanting max lumens, but after all the work this has been I’m thinking I should just make it the best beam profile/tint I can put together.

Any and all help here is greatly appreciated. :slight_smile: Y’all are obviously the masterminds of mixing. :smiley:

Light is essentially ready to assemble, D4S boards and optics will be here Tuesday.