Color temperature preferences vary by person, and by ambient conditions.
I tend towards warm CCT’s around the house, and especially when it’s fully dark, but when I need extra light working outdoors around sunset, I like to stay closer to 5000K.
If in doubt, I lean towards recommending 4000K as a decent compromise for most conditions and users.
I used to say it varies by person too, but I’m learning it’s more about the conditions the person uses the lights under. You said you work in 5000K, me too for soldering tasks. I put the 5000K in my workbench area. It helps keep my energy up.
I like warm CCT (2700-3000) in the bedroom and bathrooms because I am getting ready for bed at that time.
The ideal bulb would be cool and bright around noon, and dim and warm around midnight. But that’s not how bulbs work, so we choose CCT by the activity we do in the room and when that is.
So I guess to give a more complete answer, if bulbs came is any CCT’s, this is what I think would appeal to the widest audience:
2850K - for the bedrooms (late night)
3600K - for the rest of the home (comfortable all hours of the day)
4700K - for a workbench (a little crispness to increase your energy level without eye strain during the day)
Philips SceneSwitch “Color” bulbs allow this. They’ve got multiple LED CCT’s in them. If you turn the light on-off-on, it will cycle through 3 different color temperatures. They also have what they call “Warm Glow” dimmable bulbs that get warmer as they dim.
And I think their “White Ambiance” smart bulbs can be programmed to automatically vary their CCT depending on the time of day.
I’ve also seen some Eaton recessed light fixtures with selectable CCT’s, but it’s chosen at the time of installation with a switch, so it’s not easy to change.
I would like to check those out, I didn’t have any luck with finding them though.
My only concerns would be if they have good CRI and what the price is.
yes
for me 3500k is too yellow/orange during the day when Im indoors by a north window.
I like 3500k in the evening
during the day I EDC 4500k
my house lights are 3000k
I tried 6500k over a soldering station, but found I prefer 5600k
if I had to pick just one cct for everything
day and night,
working and relaxing,
it would be 4500k
but those are 4 different scenarios and I have 4 different CCTs for that 
Thank you very much. That’s a lot of useful information. I plan to use my quad as an EDC that’s why I am uncertain what CCT I should choose. Maukka’s measurements also add to my doubts, because diodes seem to have lower CCT than it is claimed by the manufacturer and 3500k tends to have the highest CRI overall. (Btw, could somebody explain why?).
LEDs vary within a range of ± 250 cct when they get grouped into CCT bins
I do not believe that it is accurate to say that 3500k has the highest CRI, I cannot verify that information based on the info you have provided.
if you plan to EDC during the day, I would choose 4500k, or even 5000k… some people even prefer 5700k…
but if you keep your question simple, such as is 3500k or 4500k more useful for daytime EDC, I would definitely not suggest the 3500k
3500k is quite warm during the day
it is imo a specialty CCT, for relaxing in the evening
In the case of room lighting though, it will always be up-mixed with sunlight. So the lighting might be 3500K, but the effective CCT will be closer to 5000K. If 6500K sunlight is half the total.
That makes no sense in regard to my comment about an edc flashlight
Well the purpose was to discuss how ambient light affects the final CCT.
Alright, here’s that comparison I talked about. The camera was in full manual mode, and the only setting changed for the second picture was to shorten the exposure time because the (8) E21’s were obviously brighter than the single 219B
I probably should have changed the camera’s white balance too, but it remained constant at 4000K. This isn’t very scientific, but it’s interesting none the less.
Nichia 219B NVSL219BT-V1 R9080 4000K (from Azhu’s WTS)
Nichia NVSWE21AT 5000K CCT & Bins:sm503-D240-M1-R9080 (From Virence)
That is not correct
Ambient light does not change a flashlight’s final output.
OP updated with these:
Edited version for better viewing. The processes goes like below:
- Partially cropped near the lower left center from the cross
- Gaussian blurred twice
- Exposure of each shots adjusted to match nearby shots
[Clemence]
Cool chart Clemence! Thanks for sharing.
Thanks for the chart. It really helps to sort things out. I know this is offtopic here, but please bear with me. On your web site you suggest using Pb63Sn37 solder paste, could I use Sn63Pb37 or Sn62Pb36Ag2 instead, and what are the drawbacks?
I haven’t done any testing myself, my opinion is solely based on maukka’s testing on the page 2 of this topic.
Thanks for sharing your experience.
Pb63Sn37 is a totally different alloy to Sn63Pb37. If I wrote that, that must be typing error. Please check this thread: [Reference] Physical and Mechanical Properties of Solder Alloys
Sn63Pb37 is very popular because it has many good characteristics: low melting temp, eutectic, superior wetting, good thermal and electrical conductivity, ductile, very good joint quality, and cheap. I strongly suggest this for soldering E17A or E21A if you don’t have better alternatives. Because it has low melting point and excellent wetting. This is very important for arrayed configuration when you need to clean the flux residue thoroughly. Higher temp will make flux residue gunk harder to clean. Without proper cleaning, the gunk will stay beneath the LED and later when the LED warmed, it will thin, capillary seeps out, and gets burnt.
I on the other hand prefer fluxless reflow soldering (with nitrogen gas) or use water based flux. It’s so much easier for me.
[Clemence]
Thanks for the detailed answer, I think a lot of people here will find it useful. Regarding Pb63Sn37, it is indeed written on your site to use this soldering paste for manual reflow. My fist thought was that it is a rather strange choice for soldering alloy, but I assumed that you know best, and tried to follow the instructions on your site. In your videos where you are showing a reflow process for E21A are you using water based flux? Have you tried removing it without ultrasound bath? Currently I have only fluxes that can be removed by some kind of solvent(usually I am using isopropyl alcohol), will isopropanol washing damage the led?
Finer brightness tuning plus some more info added:
[Clemence]
Without ultrasonic cleaner, the only way to properly clean the residue is to heat the module to 80C (on hot plate), let the gunk thins and flows - soak in hot IPA bath, brush it - reheat to 80C - resoak - rebrush - etc….until you don’t see any flux residue coming out when you warm the module.
Unless you want to run it hard, simple brushing in hot IPA is enough. I did super clean cleaning for VR21SP4 because it has narrower gaps at only 0,25mm. In full power hot run, without proper cleaning the flux will “climbs” to the phosphor layer. With VR16SP4, the gap is 0,4mm and won’t cause too much problem. With crowded E21A arrays, anything closer to 2A/LED requires meticulous soldering and post cleaning.
This is my first attempt with gapless design. Check the bottom picture
[Clemence]