I’m more concerning about the excessive light we continuously put outside our “caves”. Human evolved with day time/night time cycle. Face it, we’re currently in the progress of day time/not-so-dark night cycle evolution. It’s impossible to get back to the stone age. Let the science and technology slowly find the answer. In the meantime you can try your best to minimize the harmful effect (if there’s any) in sensible and practical ways.
I myself don’t have any problem sleeping/trying to sleep under any light source. The problem is when I wake up, CW hurts my eyes more than warm white.
I don’t have an incandescent to test but I tested a heat lamp with 100CRI and almost no blue light and 0.000 DUV at 2800K. I think incandescent is similar.
SW45K 219B 9080 has very high blue light intensity. I can’t find a 70CRI 4500K to compare with at the moment but it is definitely not a light to shine directly in your eyes.
I haven’t tried the SW35 yet. I haven’t tried Optisolis 6500K. I never go above 5000K unless it is for a pure thrower. I measured sunlight from 3000K to 5700K depending on time of day. Cloudy day can be 6000K+ but I prefer sunlight over cloudy day.
E21A, 2070K, 95.5 CRI, blue peak intensity of 0.07
E21A, 3061K, 96.2 CRI, blue peak intensity of 0.45
E21A 2x2000K and 2x4000K, 2828K, 94.5 CRI, peak intensity of 0.40
The SST-20, 2910K, 96.9CRI has a blue peak intensity of 0.38
The XP-L2 HD V4 7A, 3168K, 72.1 CRI, blue peak intensity of 0.76 and a DUV of –0.0029 (tint is real good btw).
XP-L HD, 2958K, 70.1 CRI, blue peak intensity of 0.39
XP-E HEW Q3 7A2, 3311K, CRI 89.8, blue peak intensity of 0.57
Nichia 219B 3000K 9080, 3391K, CRI 95.2, blue peak intensity of 0.57
Yuji, 3191K, CRI 96.6, blue peak intensity of 0.060
Optisolis 2700K, measures 2973K, CRI 97.5, blue peak intensity of 0.41
Oslon Square 92 CRI 6X tint, 2746K, CRI 91.3, blue peak intensity of 0.29
Oslon Square 96 CRI 6U tint, 2831K, CRI 95.9, blue peak intensity of 0.26
Oslon Square 92 CRI 5Q tint, 3346K, CRI 94.9, blue peak intensity of 0.61
It’s real hard to quantify blue light. The blue peak intensity above is relative to the rest of the spectrum for that emitter. The actual amount depends on the lumen output also. In order to get a good comparison of blue wavelength, you would have to overlay the graphs, which is too difficult and too much work to do. However, I think the blue peak intensity is a pretty good indicator of how much blue wavelengths is emitted by the emitter for these warm white CCTs.
If you want to experiment, visit a professional photography or theater lighting store that carries colored filter sheet material.
20 x 24 inches, sheet costs about $7ish. Pricier from Amazon etc.
Ask for a little sampler pack, often given free, with strips of all colors, big enough to cover a 20mm flashlight lens.
You can see the transmission spectrum for each filter type too.
I have a sheet of this one taped so I can flip it over the computer screen in the evening:
Nobody has suggested just dimming your lights to reduce the blue? I have trouble falling asleep, and recently installed some very dim indirect lighting and began dimming my monitor’s back-light to minimum at night. It has definitely helped. Same ratio of colors, just far less of everything, including blue.
You’re missing the point I was trying to make. Let’s delete the exercise part of what I wrote (because obviously it’s too hard :person_facepalming: ) If one is overweight and consuming too much are you going to entirely blame it on the occasional burger and chips???
How Light effects Melatonin and Sleep Posted by Wayne Caswell
You heard me mention color temperature before, and the effect of watching TV or reading on the iPad before bed (See Sleepy Yet? — How Light from Electronics Effects Sleep), but here’s why it’s important.
This WebMD article examines the hormone melatonin, which helps regulate sleep & wake cycles (the circadian clock). Melatonin production in the body is triggered by darkness and inhibited by light, and that explains why we have trouble with jet lag, shift work, and winter months with fewer daylight hours.
This Wikipedia article describes light therapy and melatonin supplements as treatment for sleep disorders like insomnia. It also describes the light color temperature, from the warm yellow of incandescent light bulbs, to blue light of the new fluorescent and LED bulbs, or the bluish tint of the iPad and TV screens.
One way to fool the body into producing melatonin earlier so you can go to sleep earlier is to select warm-color light bulbs and have them dimmed in the evening. Another way is to wear DARK AMBER or ORANGE sunglasses in the evening to block blue light (short light wavelengths). And of course, that’s why sleep experts advise against using a computer or watching TV shortly before bed.
Because my wife and I often watch TV immediately before bed, and she likes to look at videos of our granddaughter on her iPad then, I checked the iPad Settings and found a way to dim the backlighting intensity and set it to somewhat adjust automatically depending on the ambient light. Go to Settings / Brightness & Wallpaper.
I’d also like the iPad to change the color temperature at night but found nothing native in the iPad, so I searched for a reliable iPad app for that. I found iJetlag and TheSleepApp but was disappointed with both of them. One even used the wrong color of light to encourage melatonin production and encourage sleep.
Additional sources of sleep information include the two articles on this site by PhD sleep consultant Bruce Meleski (Sleep Balance – Your Path to Better Sleep and Brain Entrainment for Better Sleep and Health) and in Jeanie Wolfson’s article on Sleep: Timing of Melatonin, Light, Dark, & Use of Other Aids. Wolfson lists many suggestions for improving sleep, including these few:
Keep bedroom dark or wear an eye mask.
Keep room cool and feet warm.
Find a mattress that works for you, trying harder, softer, coil, foam, gel, waterbed, or hammock.
Block distracting sounds with white noise.
Use lighting controls to simulate dawn before alarm sounds.
Don’t watch TV, use a computer, or do homework within an hour of going to bed.
Avoid caffeine and snacks that can cause a blood-sugar drop during the night.
Establish a strict sleep/wake schedule.
Exercise regularly.
………
My take is some magical CCT of light is not the magic bullet that fixes it all. Light, any light; hinders melatonin production. Darkness promotes melatonin production.
This could be ‘scientifically’ discussed & analyzed probably forever.
But for those of us who are not really that ‘scientific’ maybe there is another way.
Get plenty of light in the daytime. [or ’your’ daytime if shift working]
Get some type of exercise.
Sleep in a DARK place.
Anything else that ’works for you’.
Yeah, that is simple & not real exciting…. but it has been working for ages.
It’s interesting to see moonlight mentioned. Would this explain full moon associated disorders?
I’ve long been trying to sort out what is ‘real’ and what is just popular belief on that matter without much success.
So….as I said (somewhere). The root of the problem is all the artificial lights we created, NOT only the blue light.
Use just enough light at night, sleep in the dark, limit night gadgeting.
I’ve seen many under developed villages in my country. Almost complete darkness in the whole village from 18:00 o’clock, no other than wood/kerosene fire at night. When it’s dark they stop their outside activities, sleeping or making babies. Yet their average life expectancy is below 50 y.o. Much lower than in the Canada or US, countries with almost no dark nights. There are more important factors outside blue light hazard.
What’s more concerning is the lights we created outside our buildings. Those light ruin our non human brother and sister.
Avoid blue light when you go to bed, for a while before bed, and during your "night". Like I said, I have blackout curtains, so despite living near a very brightly, LED-lit area that would otherwise significantly intrude into my home, I receive nearly zero outside light at night.
The biggest thing people should take away from this isn't blue light, but sleep. Sleep is incredibly important, and having a good sleep cycle is critical for your health. Not getting enough good sleep will affect you long-term. There's a lot of studies to support that in a lot of different ways.
