What lighting best replicates sunlight?

[MattPete]

...
Xicato has 4000K "artist" ones, which are something like 97+ CRI, high GAI, and high R(whatever) numbers across the range. The drawback is they cost about $30-40 each....

Yowza! I've been contemplating trying to make my own downlight using ultra-high CRI LEDs, but those prices are prohibitive.


Slightly off topic: How feasible would it be to buy an off-the-shelf bulb or downlight (preferably one with no flicker and good dimming), and simple replace the emitters (and optics, since they likely be broken while getting at the emitters)? It would sure save time trying to source a power supply, etc...

 

[MattPete]

The yellowing refers to all papers, including tissue and napkins.

I find that nearly all light sources (halogen, led, CFL) that are in the 3000k or lower range cause yellowing of white objects. It's just par for the game. Yes, under constant exposure to a light source chromatic adaptation occurs, but it is probably more accurate to say that partialadaptation occurs. After all, colors outside still look cooler on a cloudy day, and warmer when spending all day under incandecents.

The exception to the yellow effect are neodymium bulbs (e.g. GE Reveal), which scoop out the yellow part of the spectrum, and Soraa bulbs. I've done back-to-back comparisons between a 3000k Soraa and sunlight streaming in through the window, and whites definitely look yellower under the Soraa, so it's not like they are all that white. However, when chromatically adapted to a room light by various 3000k bulbs, whites look whiter under the Soraa compared to other reflectance surface in the room (toys, sofa fabric, wood floor). The whites look similar under my Solux 3500k bulb, but for other colors the Soraa looks warmer.

I'm rambling...

 

[beanbag]

Update:
So I got some of the 4000K Xicato emitters, which cost a pretty penny. By itself, the light does have a very pure white appearance. Colors look "fine", paper looks white. However, they don't match so well with the rest of the lighting in my room, which are the Bridgelux 3000K LEDs. The 3000K emitters give the room an evening warm glow, which is also good by itself. But when the lights are on together, the 3000K light looks like it has a sickly orange tan, and the 4000K light looks more "harsh".

Maybe I should bump up the rest of the room lights to 3500K?

I was also reading about the "class A" lighting stuff that Bridgelux is pushing. I think the point is that even for a given CCT, like 3000K, the class A light has a slightly different hue than the ideal blackbody curve, in order to minimize appearance of tint on whites. So in that case, I wonder if I can keep the pleasant early evening glow of 3000K without the yellowing on the paper?

 

[JoakimFlorence]

I was also reading about the "class A" lighting stuff that Bridgelux is pushing. I think the point is that even for a given CCT, like 3000K, the class A light has a slightly different hue than the ideal blackbody curve, in order to minimize appearance of tint on whites. So in that case, I wonder if I can keep the pleasant early evening glow of 3000K without the yellowing on the paper?

Hmm, I don't see any reason why LED would cause the appearance of a yellow tint on whites, besides that optical brightener effect already mentioned. Though it definitely can cause a muted yellowing tint on other colors.

I do know what you mean though. The light given off by LED often feels a bit like a faux white. Incandescent/halogen light appears like it's more warm full and orange-tinted, while LED light appears like it has a more yellowish cast (it gets better with higher CRI of course). I'm not sure why exactly this is. It probably doesn't have to do with the actual color tint of the light. (It's almost like the eye can somehow sense the lack of red wavelengths in the spectrum, I know that sounds crazy)

So yes, they do seem to sometimes try to compensate for this effect by making the light more pinkish tinted. (which I don't like)

Another possibility is some slight phosphor mismatch, where the layer of phosphor is not precisely just as thick as it should be. That would make things more yellowish, or a little bit magenta-tinted if there was too much blue light getting through. Or the manufacture may not fully take into account heating effects, because the amount of light fluorescing from the phosphor very slightly decreases and can become a tiny bit more orange-shifted at higher operating temperatures, when it starts to get hot. While the human eye is not good at distinguishing between small variations in color temperature, it is however extremely sensitive to slight differences in color tint.

 

[ssanasisredna]

While the human eye is not good at distinguishing between small variations in color temperature, it is however extremely sensitive to slight differences in color tint.

That is a gross exaggeration based out of conjecture and not fact. Based on what you are calling tint, the sensitivity is about 2x that of color temperature along the blackbody and in between say 2700 and 5K.

650px-CIExy1931_MacAdam.png


To the op:

- You can't have multiple CCT light sources and expect things to look the same. Your eye, much like a camera adapts to the predominant light it is exposed to. Adapt to the 3000K, and the 4000K will look a bit bluish. Adapt to the 4000K, and 3000K will look overly orange/yellow. You need to pick one. Your original stated goal is you wanted thinks to look like how they do under sunlight. That is not going to happen at 3000K, though high gamut area light sources will be better than normal gamut area sources. The 4000K will provide a better color balance similar to sunlight and 5000K will again be better. You just need to pick what you want to accomplish.

 

[beanbag]

I figured that I could have the rest of the room have the warm evening glow, while it is only 4000K above my desk where all my paper is. But I guess this has turned out kind of funny. I have both sets of lights on dimmers, so I can mix them.

 

[18650]

CRI truthers ruin another thread...

Personally I don't like the look of white paper under anything less than 5000K.

 

[degarb]

Halogen are good but I've found them to need bulb replacement more often as well as they just simply kick off way more heat than I want when I'm working, especially right over my head. I need 500 watts of halogen to be as effective as my single 100w 96cri 5000k MH.
I have halogen above my stove, since there's plenty of heat there already and color rendition is important when cooking but over my electronics work bench and over my art table, MH has proven most effective. YMMV.

I agree, 100 percent.

I have had halogen work lights melt into to linoleum floor. They are fire hazards. You simply cannot pretend efficiency doesn't matter. I know for a fact, that you will be seeing color way better with a 600Watt 65 CRI metal halide 80k lumen growlight with winged reflector than a 100 CRI 500 watt halogen at 10,000 lumens. I know, cause my first $200 painting light was a halogen in 1990. Efficiency matters, because resources are limited.

http://onlinelibrary.wiley.com/doi/10.1002/col.20399/full

 

[JoakimFlorence]

If you were trying to replicate the feel of sunlight, one thing you could do is take a 5000K ceramic metal halide bulb and combine that with a 635nm and 490-495nm cyan LEDs. Natural sunlight actually has a lot of cyan and light azure blue wavelengths in its spectral profile that can lend the light a somewhat softer feel. The red wavelengths ( >625nm or so) give the light a feeling of warmth and fullness.

(getting too much into detail here but >480 would be better to use than 495, if you can find it, then it would also need some more green to balance out the color of course)

A warm beam of sunshine has a color temperature of approximately 3900-4200K. If you see "daylight" often being listed as higher that's because it also includes the blue backdrop of the sky.

 

[Enderman]

A warm beam of sunshine has a color temperature of approximately 3900-4200K. If you see "daylight" often being listed as higher that's because it also includes the blue backdrop of the sky.

Unless you're talking about dawn/dusk, this is BS. Go look at a spectral analysis of sunlight, it analyzes the colour of the light regardless of the sky.

 

[degarb]

If you were trying to replicate the feel of sunlight, one thing you could do is take a 5000K ceramic metal halide bulb and combine that with a 635nm and 490-495nm cyan LEDs. Natural sunlight actually has a lot of cyan and light azure blue wavelengths in its spectral profile that can lend the light a somewhat softer feel. The red wavelengths ( >625nm or so) give the light a feeling of warmth and fullness.(getting too much into detail here but >480 would be better to use than 495, if you can find it, then it would also need some more green to balance out the color of course)A warm beam of sunshine has a color temperature of approximately 3900-4200K. If you see "daylight" often being listed as higher that's because it also includes the blue backdrop of the sky.

Joakim, can you list for me all the tools, where you bought them, for evaluating your bulbs? I ask because, as I recall, you have some accessible and interesting tools-pricewise. Or so, I recall. I could Google threads for two hours, but easier just to ask. I mix lights all the time for examination, so I don't discount that, like some. However, I only am currently able to mix work lights that I own. For me, the mix changes by the minute. I am more interested in a practical solution, though the theory is interesting,as long as obfuscation free. I firmly believe that if you understand anything, you can explain and summarize it succinctly in every day English. Otherwise, you may just be a genius able to memorize complex mean less gibberish.

 

[ssanasisredna]

A warm beam of sunshine has a color temperature of approximately 3900-4200K. If you see "daylight" often being listed as higher that's because it also includes the blue backdrop of the sky.

I would agree with you .... If you were right, but you are not. This is completely wrong. Not even remotely close.

https://en.m.wikipedia.org/wiki/Air_mass_(solar_energy)