True Color Rendition (TCR)..........

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pinkpanda3310
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As mentioned by LB green skin looks unhealthy therefore unattractive…?

  

Unheard
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pinkpanda3310 wrote:
As mentioned by LB green skin looks unhealthy therefore unattractive…?

Maybe that’s the reason, dunno. I asked because I wondered if there’s a paper about it. My first thought was that we’re used to incan lights, and so associate the lower duv with the comfort a child experienced at home. Something like this.

But yes, the higher reflection of red color makes skin look more healthy.

Smile, you cannot kill them all.

Oli
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We don’t use flashlights the same way we use sunlight. We don’t use flashlights the same way we use lights in a house. Example: you are standing at one end of a 30 foot long white (walls,floor, ceiling) hallway in a building and you’ve got a light over your head and you’ve got a light that’s down at the end of the hallway 5 feet from the wall and you’ve got one in the middle all mounted on the ceiling. You want to see a painting on the wall down at the end of that hallway. It is a large painting of a deteriorating barn in a field with some blue sky. It is autumn and the field has not been cut. You have the option to turn on any single, double or triple combination of lights that you want. These are all bare bulbs shining in all directions. And you have three different bulbs that you can put in any position you want. One 2700k, one 4500k, and one 6500k. What bulbs do you put where and what do you turn on?

Oli
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https://www.sothebys.com/en/articles/5-artwork-lighting-tips I found this article after I posed the question above. Do not click on the link until you have a good answer to the above question.

BurningPlayd0h
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Unheard wrote:
pinkpanda3310 wrote:
As mentioned by LB green skin looks unhealthy therefore unattractive…?

Maybe that’s the reason, dunno. I asked because I wondered if there’s a paper about it. My first thought was that we’re used to incan lights, and so associate the lower duv with the comfort a child experienced at home. Something like this.

But yes, the higher reflection of red color makes skin look more healthy.

Here are two studies on lighting preferences that found that for at least some color temperatures the participants prefered rosy/negative duv lights:

https://www.energystar.gov/sites/default/files/asset/document/Energy%20Star%20webinar%20Presentation%20-%20Ohno%202.pdf

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920454

It seems to be due to both perception of what light looks “white” at different illumination levels and color temps, and that greenish/positive duv light often looks especially bad. I can’t really explain why it does to me either, but I’ve hated the light from greenish, low CRI florescent tubes all my life. Interestingly some florescent lights are very rosy instead, even when 70 CRI or lower. Keep an eye out for differences in temp/tint of florescent tubes right in the same or adjacent fixtures next time you’re around them.

Unheard
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BurningPlayd0h wrote:

Here are two studies on lighting preferences that found that for at least some color temperatures the participants prefered rosy/negative duv lights:

https://www.energystar.gov/sites/default/files/asset/document/Energy%20Star%20webinar%20Presentation%20-%20Ohno%202.pdf

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920454

It seems to be due to both perception of what light looks “white” at different illumination levels and color temps, and that greenish/positive duv light often looks especially bad. I can’t really explain why it does to me either, but I’ve hated the light from greenish, low CRI florescent tubes all my life. Interestingly some florescent lights are very rosy instead, even when 70 CRI or lower. Keep an eye out for differences in temp/tint of florescent tubes right in the same or adjacent fixtures next time you’re around them.


I have one fluorescent tube left (nostalgia). My Opple measured a little over 2700K and a positive duv. It does not bother me at all, but yes, usually I prefer rosy over greenish tints. But I cannot really tell the difference between positive and negative duv. Yesterday I made experiments (not blind ones, obviously, I know my lights). With fully adapted eyes, I cannot identify the tint of light reflected from a white surface. Of course, there are limits. A sw45k D200 is outside of those limits. It is so much off that even my camera cannot find a correct WB. I’ve linked two reviews with some pictures in this thread, some of them show a rosy background. That was actually a white sheet of paper, and the light source was a sw45k, dedomed behind honeycomb TIR optics. I left it as it is since it was basically ok, but it was interesting to note that AWB didn’t work.

Ok, my idea about green/rosy is, when comparing two lights with different characteristics, one looks greenish, one looks rosy. This is really always the case in the NW range of CCTs. To me it shows the perceived tint is not necessarily tied to duv.

It is all a mystery.

Thanks for the paper and the presentation. The data is interesting by itself, even if it gives no hint about the psychology behind all this. I need to learn much more about it.

Edit: Maybe Whacky is not so wrong with his TCR. In some sense, at least. Interesting topic anyway.

Smile, you cannot kill them all.

xevious
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BurningPlayd0h wrote:
You’re discounting how relative human vision is. Shining the same light, at the same object(s) can look completely different for me based on time of day/ambient lighting. TM-30 was created to address the many serious downsides of the older “CRI” rating:

Long video, but if anyone’s bored it’s an amazing source of info.


Thanks for posting this.
As a layman in this area, I have made observations of CRI ratings in lights I’ve purchased and seen inconsistencies. This video helps explain that. Isn’t it bizarre that it has taken so many years to reach this premise that should’ve been obvious back when CRI was first established? Or was it a matter of the right people coming along who could offer up a new way of looking at light rendering?

Is it safe to say that while CRI has its merits, it’s a narrow mathematical practice that misses other variables?

I can appreciate a very keen interest in TCR for lighting sources in photographic applications. Though I’d expect professionals would be sourcing very specialized lights for that purpose and using filters to compensate. If TM-30 helps this out, that’s great. The “High CRI” lights we’ve been buying are targeted to consumers who have above average light knowledge & needs, plus the hobbyist. And yeah, they’re not all created equal or necessarily representative of claimed temperatures. And thankfully minus-green filters are available to make corrections when very much needed.

I haven’t seen the whole video, but I wonder if a TCR indication is established as part of an average. Not just in colors across the spectrum, but also with respect to the quality of ambient light, such as a sunny day versus a cloudy day… or morning versus noon.

dthrckt
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Any opinions or facts on the mixing of LED color temps to increase TCR or actual CRI?

I built a work light w/ 2 × 50W COB LEDs, 1 CW, 1 WW. Works amazing for painting walls, you can easily see where you’ve missed a spot even painting white on white (eg repainting ceiling).

Unheard
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dthrckt wrote:
Any opinions or facts on the mixing of LED color temps to increase TCR or actual CRI?

I built a work light w/ 2 × 50W COB LEDs, 1 CW, 1 WW. Works amazing for painting walls, you can easily see where you’ve missed a spot even painting white on white (eg repainting ceiling).


Mixing colors can lower duv.

Smile, you cannot kill them all.

dthrckt
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That’s a 4 emitter light that I modified. WB on 4300, seems slightly more green and purple than to my eye.

Obviously, they blend together at even 3 feet.

I don’t know what duv is, but I am curious as to why I should or should not mix 4 high cri emitters with different color temps when I upgrade this ?8 year old mod.

They’re xlm2. What would give me the greatest TCR?

I feel like true color rendition value should have candela factored in, and that’s probably my point more than specific emitters.. If what I need to see well doesn’t have enough light on it…

Probably limited to dedomes or HI for this, if it still had reflectors, probably different. Maybe lh351d? I have read a little on the latest super high cri, but for this light they sound low power with lenses or reflectors.

Unheard
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duv is a measure for how far a color is away from BBL. If you mix very low and very high CCTs, the beam can become unpleasently rosy (i.e., too extreme).

Have a look at:

https://en.wikipedia.org/wiki/CIE_1931_color_space#Mixing_colors_specifi...

(Mixing colors specified with the CIE xy chromaticity diagram)

Resulting duv can be calculated based upon x,y that you calculated with the formula stated in the above link:

https://www.waveformlighting.com/tech/calculate-duv-from-cie-1931-xy-coo...

You get x,y from the manufacturers datasheet or by measuring.

Smile, you cannot kill them all.

thefreeman
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dthrckt wrote:
Any opinions or facts on the mixing of LED color temps to increase TCR or actual CRI?

I built a work light w/ 2 × 50W COB LEDs, 1 CW, 1 WW. Works amazing for painting walls, you can easily see where you’ve missed a spot even painting white on white (eg repainting ceiling).

It increases color saturation a bit, which is an example of the things that CRI don’t show but TM-30 does, you can have two lights with an R9 of 50, with one the reds are undersaturated and with the over oversaturated (which in general isn’t as much of a problem).

dthrckt
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Thanks for the link. When I choose emitters maybe I will try doing some calculations on different bins.

Interesting point about color saturation. My highest cri longer range light is fenix fd65 (xhp35 hi NW). In my opinion you see more colors with the 4 mixed bin XMLs.

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This is an interesting thread. As a now retired small product photographer, I tried many things over the years to get get accurate color from film and digital capture. What I settled on was Broncolor xenon tubes fitted to Dyna-Lite heads and power pack, with an acetate Uv filter on each of the lights. When testing it’s never as good as shooting under mid-day sun, but as good as could be done at the time. It’s all about what is most pleasing to the average viewer. As for flashlights the same applies, as mentioned above several times. Ergo, I have a couple flashlights that make things look pretty good, mostly close in, and throwers that can get out there but don’t make objects look that great. Good for me would be a flashlight that does both, and with a red light for the night, and a case that glows in the dark, and….

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