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I'm curious about how well an RGBA LED light strip can render white light (various color temperatures), compared to RGB, RGBW and RGBWW light strips. I'd like to find some pics that demonstrate that.

I'm curious about the white rendering capabilities of the various technologies, not if manufacturer A is better than manufacturer B.

I'm not trying to select a particular LED strip (this question got closed because that person said that's what I was looking for).

I also want to point out I'm only interested in rough qualitative comparisons (keep it simple). I'm not interested in quantitative data using NIST calibrated equipment. When I was looking for an EDC flashlight, I found content that compared flashlights by shining them on a white wall and taking a picture. You can see things like one has a bluer tint than the others and it's not very uniform. I'm looking for something like that--just some pics so I can make a rough qualitative assessment.

Does anyone know of any good pics/comparisons out there? Because this can be highly subjective, I'm not looking for text only content. A statement of one being "bad" and another being "good" doesn't mean much to another person. I'd rather see side by side pictures of these lights illuminating the same white surface--and I can see how "good" or "bad" each is (to me).

I really do hope this is clear now (thanks for all the comments so far).

Thanks,

Jim

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    \$\begingroup\$ I don't think you can make any meaningful comparison of colour from RGB sources taken by a camera with RGB sensors with different centre-wavelengths and bandwidth than the LEDs and displayed on a monitor with yet another set of RGB devices with a different response. I think your question is likely to be closed as resource hunting and not an electronics design question. \$\endgroup\$
    – Transistor
    Commented Sep 23, 2021 at 21:28
  • \$\begingroup\$ I don't want to debate the accuracy thing--that's why I want side by side comparisons--it'll give me relative differences. As for resource hunting, I'm not sure what you mean by that. I AM looking for resources (i.e. websites) that have the information I'm looking for. So far, I find websites trying to sell me led strips. If this inquiry is not allowed, then so be it. \$\endgroup\$ Commented Sep 23, 2021 at 22:32
  • \$\begingroup\$ RGBA lighting is basically worthless for white lighting, but seeing that in a photograph is difficult. What you need are photographs of color test patches. Under RGBA you'll see that a lot of patches are the wrong color. \$\endgroup\$ Commented Sep 23, 2021 at 22:39
  • \$\begingroup\$ @AdirondackJim I've got buckets of software I wrote that uses the most recent CIE human color and intensity models to answer such questions if you can capture the spectrum with a spectrophotometer using a standard bench setup. (I used Ocean Optics as the cheaper spread after using far more expensive units earlier.) Are you instead looking for someone else who has this kind of setup, like I do, but is willing to go through a bunch of LED types, operated in various ways and means, and then collate all this data for you so that you can have an answer? (If so, I know I don't have the time for it.) \$\endgroup\$
    – jonk
    Commented Sep 23, 2021 at 23:02
  • \$\begingroup\$ jonk, I'm asking for something simpler. I figured (hoped) people would be curious how these different types of led strips compare to each other when producing white light at various color temperatures, took some pictures and published them on a website somewhere. That's all I want: some pics comparing the output so I can visually see the differences. (Similar to the websites that have pics comparing LED flashlight output). Thanks. \$\endgroup\$ Commented Sep 24, 2021 at 0:10

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Spectrum of RGBA LED compared to low CRI (Color Rendition Index) 6500K LED (source):

enter image description here

Just looking at the spectrum, it appears color rendition will be terrible.

Color temperature gives information about how the light itself will look, but it only gives useful information about how objects will look under that light if the light source has a reasonably continuous spectrum without holes or peaks, ie if it is close to an incandescent light. For low CRI lights which have a spectrum that is full of holes, color temperature is useless.

For example, a sodium street lamp has a quite warm color temperature, being yellow, and it has a CRI of zero, because it is almost monochromatic. That is, with this light, everything pretty much looks yellow.

Besides, the color temperature of RGBA LEDs is adjustable depending on the intensity of each LED, so there is no point in measuring it: it will cover the whole range by design.

The purpose of RGBA strips is not main lighting. It's more about stuff like signage. In this case color rendition is off topic since the light is supposed to be looked at directly or through a translucent diffuser. They're very useful for that because they have a wider color range than RGB, better white, and better efficiency when set to white.

If you want good quality light with variable color temperature, the way to do it is to use good quality warm and cool white LEDs and mix them. You can add RGB on top of that to add color if you like, and in this case the Amber LED is redundant with the warm white. But if RGBA is used as main light source, it will definitely look weird.

Spectrum of low CRI LED versus high CRI LED:

enter image description here

Basically for it to look pleasing and have high CRI, it needs to approximate the spectrum of black body radiation (incandescent or sunlight) with no peaks or holes. For efficiency and cost, it is not necessary to output wavelengths that are invisible to the eye like IR and UV, although lack of UV will make objects that have a tendency towards fluorescence look different than under natural light.

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  • \$\begingroup\$ I hate to say this, but I've already seen this information. It sounds like you're trying to help me select an led strip and I was really trying to avoid that so my question wouldn't be closed because that is opinion based. (And that's why I intentionally didn't tell anyone if I had a project in mind). Thanks! \$\endgroup\$ Commented Sep 23, 2021 at 22:34
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    \$\begingroup\$ Well you asked "how well an RGBA LED light strip can render white light", the answer is "not well" \$\endgroup\$
    – bobflux
    Commented Sep 23, 2021 at 22:50

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