Subjective thoughts on lighting, Mainly CCT

Off-topic Chatter
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I have always prioritized replicating natural sunlight using artificial illumination. My ideal specification is a relatively high CCT of 4000K or above, combined with the highest possible CRI (Re) and a broad spectrum. This combination delivers optimal color rendering, which is essential for clearly distinguishing objects. This preference aligns with human physiology; our eyes have evolved to optimize visible light that matches the natural spectrum of daylight.

Unsurprisingly, plants utilize this same visible light. A broad-band white light with a high CRI outperforms the typical “alien-like” blue and red-purple grow lights. For optimal plant growth, a combination of high CRI (Re), UV, and far-red to infrared (IR) spectrums is required. This pursuit of natural light reproduction remains my top priority.

On the other hand, humans also have a deeply rooted evolutionary relationship with the warm glow of a bonfire or wood fire. While I was intellectually aware of this, I had never truly felt it on an emotional level; especially when it came to LED lighting.

I used to hold a baseless stereotype that mantled gas lanterns or campfires are pleasant only because of their distinctive physical warmth or visual flickers, having little to do with the light itself. Consequently, I never once considered mimicking them with serious LED lighting. It was a shortsighted assumption. I thought I hate lower CCT, because of characteristic behavior of distorting object colors, making everything look overly red or yellow. I disliked this coloration, treating it as an undesirable distortion to be avoided at all costs; even though I thoroughly enjoyed my gas lanterns.

However, my entire perspective shifted when I experienced the Anduril 2 UI’s Candle Mode.

When paired with a CCT of 4000K or higher, Candle Mode felt like nothing more than a disturbing, erratic flashing. It made sense: the sun never flashes, and lightning is a sign of danger, triggering anxiety and discomfort. But when I switched to 2700K, everything changed. It felt instantly comforting for no logical reason; so cozy, warm, and inviting. I felt like I could watch it all day, and it served as the perfect background light.

Since the only major variable was the CCT, I felt compelled to investigate why. That realization led me to a new conclusion: while high-CCT daylight remains our ultimate goal for bright, functional visibility, there is an entirely separate goal for ambient mood; the wood fire. It is defined by a low color temperature, instability, and a natural flicker. It mimics the very fire that provided humanity with warmth, safety, and a cozy place to sleep since antiquity.

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(Tap the image)

Now, I am really excited to see how an 1800K emitter will perform, and I am already making plans to acquire the missing CCT variants between 2700K and 4000K to complete my collection. I am truly happy like a child!

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In recent times I’ve done a little digging into this “subject” . I’m going to throw out some generalizations. When fluorescent lights first came along most of Asia used a 6500k. And that somewhat persists with the change to LEDs even for in-home use. Historically this is partly because they are more efficient and cheaper to make.

Western countries preferred more neutral fluorescent or warm and that persists with the changeover to LEDs especially for indoor use.

I don’t currently use any flashlights above 4000k and most are 3000k.

And if I’m outdoors I typically have sunglasses on. So whatever that sunlight CCT is, I am lowering it. Even on a cloudy day,

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Also, real fire doesn’t just change in intensity—it also changes in temperature, and it’s not the same temperature everywhere. It constantly mixes and modulates its CCT and tint.

Most LED lights are still far from simulating this. Even high-end, high-CRI LEDs have an extreme lack of deep and far-red output compared to fire.

I think we’re all missing out on a quality of light because LEDs are optimized for efficacy. Since our eyes aren’t very sensitive to the longest wavelengths, manufacturers tend to leave them out because they don’t contribute much perceived brightness. I would argue the opposite—we should actually include more deep and far red, precisely because we’re less sensitive to those wavelengths.

That said, I still own and use some incandescent lights for special occasions. For example, I have halogen lights in the kitchen because they simply produce unmatched colors.

And for cozy, warm lighting, nothing beats a high-wattage, low-voltage incandescent lamp dimmed down to very low power levels. It creates a pleasant, warm glow that no LED has quite matched yet.

But if you want 3,000+ lumens for two hours from an 18650-powered flashlight that fits in your pocket, compromises have to be made. One of those compromises is the lack of deep and far-red output.
Also, real fire doesn’t just change in intensity—it also changes in temperature, and it’s not the same temperature everywhere. It constantly mixes and modulates its CCT and tint.

Most LED lights are still far from simulating this. Even high-end, high-CRI LEDs have an extreme lack of deep and far-red output compared to fire.

I think we’re all missing out on a quality of light because LEDs are optimized for efficacy. Since our eyes aren’t very sensitive to the longest wavelengths, manufacturers tend to leave them out because they don’t contribute much perceived brightness. I would argue the opposite—we should actually include more deep and far red, precisely because we’re less sensitive to those wavelengths.

That said, I still own and use some incandescent lights for special occasions. For example, I have halogen lights in the kitchen because they simply produce unmatched colors.

And for cozy, warm lighting, nothing beats a high-wattage, low-voltage incandescent lamp dimmed down to very low power levels. It creates a pleasant, warm glow that no LED has quite matched yet.

But if you want 3,000+ lumens for two hours from an 18650-powered flashlight that fits in your pocket, compromises have to be made. One of those compromises is the lack of deep and far-red output.

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One more interesting difference is the preference for indoor lighting.

As far as I know, East Asian homes are typically equipped with brighter, direct ceiling lights.

In contrast, European and American homes tend to rely on softer, dimmer, indirect lighting. In these Western regions, bright direct ceiling lights are often seen as more suitable for workplaces and offices.

My theory is that this might stem from differences in outdoor activity habits. Perhaps people gravitate toward the type of light they encounter during peak exposure times out of familiarity, or conversely, they might avoid it to prevent fatigue. It could easily be a combination of both.

It was great reading your thoughts!
Personally, I prefer staying around the 4000K range for map reading and outdoor navigation, but who knows how my preferences might change in the future!

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Nice point!!

IMHO, a realistic solution for this right now is using two different torches (e.g. 1800K and 2700K) in candle mode, supplemented with some external 730nm emitters.

That said, simply carrying two different low-CCT torches with candle mode can already get you most of the way there. If you’re a single-emitter purist like me, you might not be a huge fan of this setup, but anything else is virtually impossible to implement at the moment. Especially that brightness and form factor.

I still prefer a two-track approach to lighting. I like to keep things separate: using a bright, steady, and relatively high-CCT light to mimic daylight, while using a dimmer, warmer light to simulate real wood fire. *I believe that a huge, real fire is threatening and therefore has the potential to cause anxiety when it’s not dim enough especially in hot summer night, just like a high CCT candle mode is unpleasant.

I honestly wish someone would implement a low-power candle torch featuring the Nichia Optisolis, but unfortunately, it seems that particular emitter has been completely sidelined by the flashlight industry.

I am glad to hear your in-depth reflections and thoughts!

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Don’t forget… !
The “white - bright” light is closer to the day light, and many people are choosing it because of that !
But don’t forget that the “less white - bright” light (yellowish - orange - rosy), is much comfortable on the eyes !
Is something similar with house lights , and with the tv, and with the night mode on the phones… etc… !

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How about a dual channel quad light with 1800k and 2700k emitters? Like the D4V2 or something similar.

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That is a valid point!

In my opinion, if the light is bright enough with a sufficiently wide hot-zone, it is natural to go for white-white, deceiving the eyes into thinking it is daylight. On the other hand, if the light is localized and has significantly lower illuminance compared to the sun, mimicking fire feels more natural and comfortable for the eye. Furthermore, this would actually cause less chemical load on the eye’s photoreceptors.

For displays…

Circle of Confusion
Circle of Confusion800×600 53.5 KB

(Audio Musings by Sean Olive: Audio's Circle of Confusion)

Media’s circle of confusion. Always reproduction is HARD!

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With 730nm AUX/Tint light that will be fantastic!

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True true… ! Even on a radios, they are playing with deferrent sounds the stations that they mostly are talking, and deferrent the stations that they mostly are playing songs !

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This is a very sensible hypothesis explaining the general preference for high CCT at high intensities, and low CCT at low intensities. This phenomenon has a name: Kruithof curve - Wikipedia

In my experience, the greatest weakness of LEDs is not deep red but blue and cyan. As picky and snobbish as I am, I could not tell a difference between the Seoul Sunlike 5700K and noontime sunlight, even though the former has only a fraction of the latter’s far red. But the difference between a 519A and sunlight is painfully obvious: the blue spike and cyan dip makes everything look pale even without a side-by-side comparison; in particular, reds under 519A look much worse than the SunLike, even though the 519A has a bit more red in the spectrum!

The lesson here is that if you want to make one color look accurate, you actually need the spectrum to be uniformly good across all colors. In particular, the easiest way to improve red rendering is not to add more red, but to fix the irregularities in the blue-green region!

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If you have a 2-channel light with warm and cool LEDs, activate candle mode and switch it to the “auto tint” channel mode. This makes it change CCT as brightness changes. Or on the LT1S Pro, there is a 3-way auto-tint which goes from red to warm to cool.

I’ve been meaning to add a dual candle mode on 2-channel lights, with each set of LEDs flickering independently… but I keep forgetting.

Usually what I do is put two lanterns in candle mode, with auto-tint. This provides a sense of motion while the color temperature and brightness change.

It’s also technically possible to change the CCT and tint with just a single LED, if it has the correct types of power circuitry… but it’s not recommended. Running a steady brightness at constant current, then switching to much higher current (with PWM to keep the brightness the same) causes the LED to change color. However, it’s not really practical to do this… it’s basically just a party trick. I tried it once with a FET+1 driver, switching between the FET and the +1, and it was neat to see the color change, but it’s hard on the LED and requires very careful calibration and only works at a specific battery voltage.

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This would be awesome!

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As a kid of the 1980s, residences were lit with incandescents, making extremely brown decade made even moreso with such red-heavy lighting. Probably why darkened living rooms lit with a CRT TV were so intensely blue.

I’ve experienced enough everything looks yellow and have no desire to return to an era of green deficiency and near-absence of blue.

I slipped when the first LED bulbs become available and paid happy happy money for the original Philips alien head in 2700K, only to discover that it was genuinely difficult to read under that light. I’ve settled on 3500K for bedrooms I spend no time or primarily sleep in, otherwise 4000/4500K for utility spaces. I had 5000K in the home office that I swapped for 4000K high-CRI and that was an adjustment for a week or so; whenever eventually expire or I find use for them elsewhere I’ll swap for something cooler / high-CRI - perhaps 5000K again.

Now do I occasionally enjoy wood wire or candle light CCTs? Sure. But I’ll just light a candle or an oil lantern whenever that mood strikes me.

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Thank you for leaving such a detailed and informative comments!

Checked!

Right above the photon pump.. Direct Blue + Fluorescent approaching’s inevitable deep

Nichia used two different pumps for their Optisolis 5000K and 3000K ← when it mixed up, we smile.

Interesting difference between Optisolis and Sunlike:

Optisolis → limiting UV is one of their main concern. Prevent accelerating aging and degradation of lighted objects.

Sunlike → Extending spectrums even some UV range is the mission, just as its name.

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@ToyKeeper Without your excellent UI implementation and candle mode, it would have been much harder for me to notice these facts.

It is also really cool that great, practically feasible improvements are available in multi-channel configurations. Thank you again!

I also recommended a product with the Anduril 2 UI to a friend who uses it for semicon equipment inspection :wink:

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While not perfect, the advantage of each today is that you can choose the one that best suits the situation and purpose. However, I strongly agree that excessively low CCT should not be used for lighting in main critical tasks. If there were a 5000-6000K option that is very very similar to sunlight, I would choose it without hesitation.

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I built a special circuit about a year ago to demonstrate exactly this party trick… at a party.

It was basically a constant-current circuit charging a low-ESR capacitor with an LED in parallel. The LED was switched by a MOSFET driven by a function generator with a variable on-time.

This kept the average current through the LED constant and adjustable, so the average brightness stayed (more or less) the same. However, with short duty cycles, all of the charge stored in the capacitor had to flow through the LED in a very short time, which changed its tint and CCT.

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To each their own as this is a need where the market provides a wide variety of options.

Although context is a funny thing: I can visit a place that I know is lit with 3000K or 2700K and that just becomes the frame of reference. Conversely for portable lighting where the context is primarily darkness, low CCTs seem even more red-yellow than room illumination.

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OG versions of LED bulbs were pretty primitive.

As the tek evolved, some mfrs (Philips?) got creative with dimming and actually had red emitters to warm the CT as the light dimmed!

I remember articles about that, including the driver chips, in trade rags like ECN and EDN. Mfrs actually gave a shiite about quality of light, and worked hard to try to replicate it.

Later, when consumers showed they didn’t gaf, or didn’t want to pay the $$$ for warm dimming, or mfrs just went into penny-pinching mode, or a combo of all three, but they stopped all that and went with single channel “white” emitters.

It got worse when they slapped in huge COB white-emitters, then huge COB blue emitters surrounded by a plastic phosphor-covered shell that would do the conversion externally.

The latter were those bug-eye-looking bulbs that were yellow when unlit. Horrible light quality, and smaller area so needed a huge shade to diffuse the light.

Then, of course, we got the typische snowcone bulbs with discrete cheap emitters peppered all over an Al baseplate.

So the circle is complete. Crap bulbs with one CT, then nicer variable CT bulbs that matched the BBL, then back to shiite but more efficient single CT bulbs.

Ah, “remote phosphor”. That’s what they called it.

These hideous things…

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