Mixing RED emitters with cool white ones (MC-E) ???

Hello All,

has anyone made experiences in mixing red emitters with cool white ones in a multi-emitter setup?

I'm currently building a multi MC-E light using beside MC-E equipped wit TIR optics some MC-E without any optics for pure flood light. Concerning these flood LED group I thought of adding some deep red emitters to improve color rendering when using the light outside in the nature.

The question is how many red emitters do I have to use per white emitter?

I would like to use the cool white ones because of the higher efficiency over the neutral or even the warm white ones.

Further info: I don't want to use my light for painting pictures; I'll use it outside in the woods for running or walking, perhaps biking. So I want to achieve good contrast in this environment.
And: When doing night barbecue, it would be nice when the color rendering would be that good one can distinguish whether a piece of meat is done or not

(@2xTrinity: I read in some threads that you already build lights using this setup, but didn't find find the thread)

Thanks for any help,

Regards,

Holzleim

If you haven't purchased the MC-Es yet, I'd recommend you get the 6A warm emitters from cutter.com.au Those are incidentally the cheapest ones offered (and IMO, the best).

The results I've erceived with these as far as color temperature and color rendering are very comparable to, if not better than, my old cool + red mixtures, without any color mixing difficulties. I can also get almost as much light from one MC-E as I used to get from a 4 white :1 red array.

To see what this color temp looks like relative to others, check out my thread with my tri-MCE mag here. The 6A is about 3700k (just slightly cooler than my 3500k fluoros at home, or my 3300k incan flashlights)

Having used these, I wouldn't go back to mixed arrays of white + red, as the color rendering is about as good, but without color mixing issues. Compared to fluorescents, these do tend to exaggerate the brightness of saturated blue objects just slightly, but other than that, I have no complains with color rendering at all. 5A is also quite nice, I have one in my LF2x at the moment (my EDC) At 4200k it's considered a neutral white bin, and even this suffers just about no "lack of red" problem like the old cool white bins. Cutter does have a neutral MC-E but they don't specify a bin, so chances are it's probably a 4x or 3x bin (eg closer to a cool white), which I haven't personally tried.

I also have some 7A bins in XR-E, and I don't like those as much -- once CCT is that low the LEDS start to look too much like half-dead stock maglites to me, and efficiency begins to take too much of a hit. In my experience they do a better job at mimicing incans than CFLs do though, so CRI is certainly not too bad -- I just don't like the color temp that low.

To answer your original question however -- the amount of red to be added does not need to be very much at all. The goal is just to correct for a deficiency in the cool white LEDs, so probably one red emitter driven to ~350ma such as a Lux-III or one of the red Crees from DX culd probably balance a singel cool white MC-E, or up to 4 separate XR-Es driven at ~700mA.

One concern with red sharing a common heatsink though is that for long duration runtime, the reds are more sensitive to temperature, so the red may weaken as the heatsink heats up, and you may want to start with slightly more red in the mix initially.

Though I haven't tried it, you may also consider using some warm white LEDs like the 7x emitter from Cutter to balance out cool whites. Efficiency and CRI will be a wash compared to using all neutrals though.

Thanks for your quick response and the info.

I think I'll go for a mixture of 6A(320Lumen..350mA) and WH(430 Lumen...350mA) for my flood light in relation 1:2 along with one red per cool white. Then I can adjust the color rendering by fine tuning the current for the various led groups.
For led group with the TIR optics I think I'll go for a mixture of the 6A and WH of 1:1 because here I have no further space available for adding red emitters with optics.

At the moment I'm still doing the driver and control electronic and waiting for the various MC-E optics to come out, so I think it will take some additional week until I will finish my light......

Holzleim said:

Thanks for your quick response and the info.

I think I'll go for a mixture of 6A(320Lumen..350mA) and WH(430 Lumen...350mA) for my flood light in relation 1:2 along with one red per cool white. Then I can adjust the color rendering by fine tuning the current for the various led groups.

Click to expand...

Sounds like a good mix. You should end up with a high CRI neutral white blend. At some point I want to make a good desk lamp fixture with a setup like this to allow tunable color temperature, eg able to tweak the ratio between the warm, cool, and red.

Also, with the warm whites in the mix, the color mismatch of the red and cool white in the "fringes" of the beam where they dont' quite overlap won't be nearly as obvious.

For led group with the TIR optics I think I'll go for a mixture of the 6A and WH of 1:1 because here I have no further space available for adding red emitters with optics.

Click to expand...

This is a good choice. reds and whites are fairly easy to mix when the light is diffuse, but not when they are collimated with optics, so there the warm/cool blend will probably produce cleaner looking results.

What about the "dip" in the green parts of the spectrum?
Most white LED's have peaks in blue and greenish/yellow parts, with a huge honking gap in between (cyan) and a dip in "proper greens". That's the reason they render foliage poorly and give a bad impression of depth outdoors.

Has anyone had experience with mixing multi white with 1 red and 1 cyan emitter?