I really like the tint of the three SST-20 I got from KD, even if it’s above the BBL.
EE X6 SST-20 4000K CUTE-3-SS optic (left) BLF Q8 XP-L HD V6 3D (right)
I initially put 4 of them in my D4, but I mainly use it indoor on lower levels…
So I replace 2 of them by some 3000K variant.
Now I have a 3500K ish beam with a nice CRI 
How do they compare in tint. I have the 3000k’s and love them. Still in doubt to try the 4000k’s.
It is a great way to end up under the BBL, what we all love so much (but is considered as undesirable in the lighting industry).
( from: https://store.yujiintl.com/blogs/high-cri-led/revolutionary-tunable-white-led-yuji-spectrum-x-series )
The 4000K on their own are quite pleasant, at least under TIR (didn’t try in a reflector).
What I really like is that they have a small die (like XP-G2) so the throw is improved compared with 219C
Thanks for the link djozz! It explains why some experienced members tend to say that tint-mixed beams are so good.
Or you could have two greenish emitters, and as long as they are sufficiently far apart CCT wise, it’ll work as well.
That's very interesting! So "average tint" is always somewhere on straight line between CCT1 and CCT2?
By using logic, it seems it's better to use two LEDs with large CCT difference, at least when below BBL is desirable.
3000K+5700K seems to be best combination for most LEDs.
I wonder what is the procedure for 3+ different CCTs?
With three emitters you could theoretically cover the whole triangle they create by adjusting the output.
With the Zanflare T1 and its infinitely adjustable CCT, the effect on two emitters is clear as well.
Yes, it's very easy to see from that graph why is better to use 3000K+5700K emitters than 4000K+5000K emitters to get ~4500K tint, first combination has much better chance to be under BBL.
Yes, the 2700K to 6500K tint mixing should be done with an additional set of 4000K leds in between - I tried to tell this in the BLF lantern topic weeks ago for the exact reasons, which your last figure shows.
Thanks for those helpful graphs. My quad E21A 2500k with 2x 2000k and 2x 3000k is much rosier than just 4x 2000k or 4x 3000k variants. My quad E21A 3500k with 2x 3000k and 2x 4000k is rosier than just 4x 3000k or 4x 4000k.
From my observation, comparing emitters of the same CCT, below the BBL tint does not seem to tint objects as much as above the BBL tint so white objects look whiter with below the BBL tint where as white objects look yellowish/greenish with above the BBL tint. I’m guessing this is why members here said they feel mixing CCT improves color rendering eventhough all it does is give you more below the BBL tint.
The perceived tint deviation must have to do with the eye/brain relative sensitivity to the different frequencies of the visible spectrum:
Source: Light Measurement @ TutorVista.com
:-)
Wow…
Surprised to see it works like that.
But why CRI drops, it doesn't make sense?
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?
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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
This is why I love that red dot in that graph (and the 99 color samples as well, but for a different reason).