Author Topic: Workshop Lighting - Warm White or Pure White?  (Read 19941 times)

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Offline apis

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #100 on: January 12, 2019, 11:48:19 am »
My understanding is that it depends on the wavelength of the light, not the white light color temperature.
The cells that regulate the biological rhythm are more sensitive to blue light, so if you have lots of blue light the body thinks it's the middle of the day. On a screen you can turn down the blue component which makes everything look warmer. But if you only make a white light warmer by adding red color you still have the same amount of blue.

For indoor lighting during the day it should be better to have more blue light in the mix, and in the evening you would want less blue to help the body adjust its rhythm.

This is just my impression, I might be wrong.
 

Offline Edison

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #101 on: January 12, 2019, 09:31:04 pm »
I have a so-called biological alarm clock, it's shaped like a ball, and it's not just a shape that mimics the sun.
Can mimic the sun light, when I go to sleep, I can light it like a lamp - it gradually changes the color of light and the brightness from white to dark red (sunset), in the morning it goes from the red to the white and it can make the sounds of the awakening of nature (sunrise) - this takes about 30 minutes .
« Last Edit: January 12, 2019, 09:36:58 pm by Edison »
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Offline SeanB

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #102 on: January 13, 2019, 01:03:42 am »
Lower colour temperature is preferable before sleep. I have two hue bulbs in a fixture in my bedroom and half hour before sleep I put them on very yellowish light and dimmed to low lumens, 15 minutes before sleep I put them on another preference setting making it orange and even lower lumens.
I kind of imitate the sun going down and get sleepier.
Ofcourse you can not read a book anymore and phone ir pad usage is not preferred although they nowadays also have a night setting with lower colourtemperature.

TV or PC is very cold white for good colourrendering, I thought about 6500K, and should be avoided at least an hour before bedtime, it will just upset your biological rhythm.

I am no expert but there must be tens if scientific articles about it.
Google "sleeping and color temperature" and "light and biorythm" that sort of keywords should result in many hits.

Each person is unique so you might want to experiment, write down your light and times before sleeping and next morning how you slept. Find your own optimal lighting formula. Some people are night owls some are early raisers.

The biggest win I myself have gained is with waking up with light with the lightalarmclock. Since I have that my wintermood when awakening is gone. I was always grumpy and miserable when my alarmclock went off in the cold and dark wintermornings. This lightalarm starts with very low red light 20 minutes before time to wake up and goes to bright warm white light when it is time. Works for me.

Did that as well, took a cheap LED clock radio, and voided the warranty on it, after checking the clock itself worked. Cut the main board in half to leave the clock side mostly there ( there was a bit of the radio board components left, but they were effectively disconnected) so there was room to fit in a hockey puck sized opto relay block, and wired it up to give a switched mains output, leading outside the case to a US in line socket. Standard bedside light then plugged into it, and for light I use a somewhat old ( as in pre war) 16 candlepower Siemens carbon filament lamp in the lamp itself. Wake up to a warm light that comes on a half hour before sunrise in winter, but in summer it is disconnected and put away, as the sun rises at 5AM then and I will wake with it through the curtains. Do not need the extra heat added to the current summer indoor of 29C and 60% RH.
 

Offline Kjelt

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #103 on: January 13, 2019, 05:18:47 am »
My understanding is that it depends on the wavelength of the light, not the white light color temperature.
The cells that regulate the biological rhythm are more sensitive to blue light, so if you have lots of blue light the body thinks it's the middle of the day.
This is just my impression, I might be wrong.
No you are for the big part correct, they have discovered sensors in the eye that are very sensible for the wavelenghth of blue light which regulate your biorythm.
The part you might miss is that white light expressed in colourtemperature follows the black mass radiator curve (see wiki in previous post) and that lower colour temperatures have less to none bluish light in their spectrum while higher colourtemperatures have more to much bluish energy in their spectrum.
So the black mass body radiator curve follows the sun, from rise (little blue) to noon ( much blue) to set ( little blue again).
Probably evolution has done the rest.
 

Offline apis

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #104 on: January 14, 2019, 05:56:09 am »
The part you might miss is that white light expressed in colourtemperature follows the black mass radiator curve (see wiki in previous post) and that lower colour temperatures have less to none bluish light in their spectrum while higher colourtemperatures have more to much bluish energy in their spectrum.
That is only true for black body radiators, like the sun, halogen or tungsten lights. LEDs and fluorescents don't have a nice black body spectrum. That is why they have less good color rendering index than tungsten. To get light that looks white all you need is a red green and a blue led, and then you can vary the intensity of each component make it look like any colour temperature you want. That is how computer monitors work (as I'm sure you know).

Say we're working at a lamp factory that are making lamps with adjustable color temperature. One way of doing it (I'm not saying this is how they do it, but it's a possibility) would be to have cold white LEDs + an orange LED. Then to turn down the color temperature you simply increase the amount of orange light while the blue component remains the same. Now that I'm thinking about it, it would probably make more sense to do it the other way around: have a warm white light and add some blue to make it look like higher temperature, but who knows.

If you try to simulate twilight by just adding red light then it won't work, since they eyes still get the same amount of blue.
 

Offline Kjelt

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #105 on: January 14, 2019, 06:00:40 am »
To get light that looks white all you need is a red green and a blue led, and then you can vary the intensity of each component make it look like any colour temperature you want. That is how computer monitors work (as I'm sure you know).
no i thought they only had fluotubrs or white leds backlght and they "fake" the colortemperature by the lcd panels offset.
 

Offline apis

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #106 on: January 14, 2019, 06:24:17 am »
To get light that looks white all you need is a red green and a blue led, and then you can vary the intensity of each component make it look like any colour temperature you want. That is how computer monitors work (as I'm sure you know).
no i thought they only had fluotubrs or white leds backlght and they "fake" the colortemperature by the lcd panels offset.
That's right. The lcd filters the light from the lcd backlight through a red, bule and green filter. So you can lower the color temperature by letting through less blue light... But it depends on the display technology. (The point was only that you don't need a black body spectrum to generate white light.)

Actually that makes me wonder what kind of LEDs they use as backlight in LCDs, it would be more energy efficient to create the backlight using a combination of red blue and green LEDs. But since they previously used phosphorus based backlights it might be easier to just use phosphor coated blue LEDs.
« Last Edit: January 14, 2019, 06:31:35 am by apis »
 

Offline Kjelt

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #107 on: January 14, 2019, 10:04:33 am »
It would be very difficult for flat panels to get a good to perfect colourmixing of rgb leds for it to become uniform white.
 

Offline steve30

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #108 on: January 16, 2019, 06:26:12 pm »
Are T8 bulbs considered to have good CRI?  Or is that strictly a LED thing?   Thinking of putting some fixtures in my computer room.  2 dual bulb fixtures should do the trick.  I have a lamp stand with a single LED bulb now but not quite as bright as I'd like it.  I do plan to do some YT stuff in there as well.

The modern bog-standard tubes have a CRI of >80 and are pretty good, but not as good as the more expensive tubes that have a CRI of >90.

Tubes with a >90 CRI are available from Osram and Philips. I have them in both T8 and PLL form factors. Pretty sure you can get them in T5 as well.

If you go to proper lighting supplier you should be able to select an exact product and the specification will be listed with CRI, colour temp etc (as opposed to a hardware store where the only options will be something vague like 'T8 Tube').
 

Online coppice

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #109 on: January 16, 2019, 11:31:44 pm »
Are T8 bulbs considered to have good CRI?  Or is that strictly a LED thing?   Thinking of putting some fixtures in my computer room.  2 dual bulb fixtures should do the trick.  I have a lamp stand with a single LED bulb now but not quite as bright as I'd like it.  I do plan to do some YT stuff in there as well.

The modern bog-standard tubes have a CRI of >80 and are pretty good, but not as good as the more expensive tubes that have a CRI of >90.

Tubes with a >90 CRI are available from Osram and Philips. I have them in both T8 and PLL form factors. Pretty sure you can get them in T5 as well.

If you go to proper lighting supplier you should be able to select an exact product and the specification will be listed with CRI, colour temp etc (as opposed to a hardware store where the only options will be something vague like 'T8 Tube').
Two lamps which claim a CRI of 90 can be very different in their illumination properties, so don't be too trusting of CRI scores. CRI is very gameable, which is why the industry is trying to move away from it, and use TM-30 instead. Both white LEDs and fluorescent tubes use phosphors to generate white light, so they are subject to similar limitations when trying to achieve a high CRI or TM-30 score. Phophors do not give black body type spectra. A mixture of phosphors is used to fudge an approximation to a black body spectrum. However, even the best fudging results in quite a spiky spectrum. How the peaks and troughs of that spiky spectrum align with peaks and troughs in the reflection pattern of an object can significantly affect its perceived colour.
 

Offline macboy

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Re: Workshop Lighting - Warm White or Pure White?
« Reply #110 on: January 17, 2019, 01:02:38 am »
Are T8 bulbs considered to have good CRI?  Or is that strictly a LED thing?   Thinking of putting some fixtures in my computer room.  2 dual bulb fixtures should do the trick.  I have a lamp stand with a single LED bulb now but not quite as bright as I'd like it.  I do plan to do some YT stuff in there as well.

The modern bog-standard tubes have a CRI of >80 and are pretty good, but not as good as the more expensive tubes that have a CRI of >90.

Tubes with a >90 CRI are available from Osram and Philips. I have them in both T8 and PLL form factors. Pretty sure you can get them in T5 as well.

If you go to proper lighting supplier you should be able to select an exact product and the specification will be listed with CRI, colour temp etc (as opposed to a hardware store where the only options will be something vague like 'T8 Tube').
Two lamps which claim a CRI of 90 can be very different in their illumination properties, so don't be too trusting of CRI scores. CRI is very gameable, which is why the industry is trying to move away from it, and use TM-30 instead. Both white LEDs and fluorescent tubes use phosphors to generate white light, so they are subject to similar limitations when trying to achieve a high CRI or TM-30 score. Phophors do not give black body type spectra. A mixture of phosphors is used to fudge an approximation to a black body spectrum. However, even the best fudging results in quite a spiky spectrum. How the peaks and troughs of that spiky spectrum align with peaks and troughs in the reflection pattern of an object can significantly affect its perceived colour.
This is good, accurate information.

However, given no other concrete data I would absolutely buy an LED bulb with a 90 CRI rating over a 80 CRI or an unspecified one. About a year ago I bought a few "90+" CRI LEDs and I was quite impressed with the color rendition and just general look/perception of the light. In fact I was so impressed that I went back and bought many more and replaced nearly all the other working LED bulbs (and a few CFLs) around my house with these new ones. I was lucky that they came in many form factors, including normal E26 frosted bulbs, flood lights, and candelabras, as well as GU10 floods. I used them all.

I recently acquired a Spectrophotometer (thanks, Santa/DW), so I thought I'd take a few measurements. My favored "90+ CRI" bulbs measure at 91.6 CRI according to my device (and ArgyllCMS software). Every other LED around the house measured less than 81 CRI. The most pleasant white temperature to my eye is 3000K, but I'll qualify that: that is at night (no sunlight mixing), and it happens to be the white temperature of the nice 90+ CRI bulbs. Some other bulbs with 2700K or 3300K also have a poorer CRI so that may bias my opinion. For reference, a small 20 W halogen desk lamp measures 99.2 CRI, with a white temperature between 3000 and 3300K (I forget exactly, but I'll update this post with the number). That halogen lamp sits next to my color printer in the office. Guess why! If anyone is interested I can post the actual spectra of the various LEDs.
 


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