Are you guys looking at fabbing your own LED dies?
The actual spectrum of commercial LEDs is all over the place when you start measuring it it with a spectrometer, even when they supposedly have a high CRI. Especially if you want some temperature that isn't 6500K.
It was so bad that when I was building a night light for my eink desktop I ended up using halogen bulbs which I could undervolt. The main issue was that I wanted to be able to shift the spectrum of the lights from natural sunlight at noon, down to candle light at night.
I did have big plans for doing a neural network to control a bunch of LEDs against a reference temperature, but having to build and calibrate a spectrometer and jig as part of a back prop algorithm was a bit beyond my interest, especially since for halogens I just needed a lookup table with temperatures to voltages that worked for all the bulbs from the lot I used.
there are companies that can do custom phosphor formulations for you to target a specific output. The minimum order quantities don’t make it practical for DIY but not too bad for a small startup. Our approach is to mix a bunch of different LEDs together to get the color and spectrum we want. Check out telelumen.com for an example that uses 16 chips. These are designed for researchers
I was doing something very similar to telelumen but given the variation in LED spectrum you could get off aliexpress in 2020 I could never hope to match their quality without tuning each led separately.
Looking at the spectrum graphs for your lights I'm seeing the telltale phosphor coating spike for both warm and cool white leds. An understandable tradeoff, but with the brightness of monochromatic LEDs you can get today one that's not essential any more.
With the drop in costs for both controllers and pcbs since then you should be able to get telelumen quality temperature spectra without the matching price, especially if you can get LEDs that have consistent spectra for their nominal wavelength - you only need to tune the controller once instead of for each light.
Yes, the more LEDs you mix the closer you can get to your target SPD but more LEDs also add cost and may not fit mechanically depending on how you are mixing them.
One other variable is energy efficiency, there are a lot energy codes around the world that limit how much energy you are allowed to use to light a space. In California for example it can be 0.6w per sqft. Sunlight is more like 100w/sqft so you end up having to optimize the spectrum for what humans can see and feel. I like to compare it with jpeg compression for light. In jpeg we throw away components you can’t see very well, you can do the same for light for an energy efficiency sake and maintain a close perceptual proxy.
We found 4 chips is a minimum bar for good light and use 5 for virtual sun - more info: https://www.innerscene.com/products/circadian-sky/CircadianS...