My name is cu42 and I approve of this message!! high CRI fan here.
I never put much thought into whether any high cri could be more efficient at medium outputs since as a newb I am always focused on the max numbers.
I was originally thinking the warmer 3k was the way to go for a camp lantern, but now wondering if high CRI at 4k would be more desirable than lower cri warm tint? Is there even such a thing as warm high cri?
Last I checked, daylight tends to be around 5500K mid-day, but it gets warmer in the morning and evening as the sun gets low in the sky. At sunrise/sunset it can be below 2000K. Moonlight tends to be around 4000K, but is generally too dim to activate cones for color perception.
The Kruithoff curve shows in what brightness range a specific CCT is perceived as comfortable. Sunlight with 5500K is comfortable because it is so bright! It also shows why cloudy days with very high CCTs and rather low brightness can seem uncomfortable.
Since lanterns usually produce floody light with low lux numbers, they need to have a low CCT <=3500K to be comfortable. A perfect lantern with a large brightness range would adjust its CCT with the brightness.
This is of course all somewhat independent of CRI. The CRI should be high regardless of the brightness and the tint should always be close to the BBL.
It would be an even more special project if the CCT changed continuously with ramping the brightness (sort of following the Kruithof curve) . It would require leds of two colour temperatures (say 2700K and 4500K) well blended in the beam, controlled by two separate pins of the MCU.
And a fair bit of programming and tuning a new ramping table.
That would make a good option indeed for those who like to change the color tint for different used, but as you said would require more components and drive the price up for the lantern.
Here are 80CRI 3500K LEDs too if you want something warmer. They would also be even higher output than the 4000K 90CRI though I realize that isn’t needed in this lantern.
No offense intended, but didn’t we kinda chat about this yesterday? Digikey carries 8 varieties of the LH351D that are available by the piece, but they don’t have any stock of the 90 CRI - those appear to be special order. It would be nice if they stocked those as well, though.
Either way… I personally feel that 80 CRI would be good enough for campground usage, but I’m definitely not a CRI snob and I don’t mean to spoil anyone’s fun that has an appetite for 90+ CRI.
That’s probably pretty do-able. It could use 1x7135 for a warm tint and 3x7135 for a cool tint, or maybe 2 and 2, or 2 and 3, or something like that. If it’s intended to always be warm when low and cool when high, it wouldn’t even require any code changes — just a new ramp table.
Or it could do manual color temperature changes — a single ramp which splits into both emitter types based on a user-adjustable balance.
Or it might be possible to fit both.
If the hardware has two individually-controllable tints, I can find a way to make it work. The main questions are whether the idea is worth doing, and how exactly it should work.
Creating the firmware and designing the board circuit is out of my capability range, but Toykeeper i believe can chime in on that idea. In this case a similar LED star as the Q8, but with pads for eight LEDs, with dual input paths for four each of 3000K & 4000K. (maybe we can get some of the other Q8 developers in on this project too. hints