LED Color: Warm vs Cool White

I myself would prefer cool white at my workplace/shop (and kitchen and bathroom). While personally preferring low light at the rest of the house and no light watching TV.

When you watch TV, have a light on behind you to give general illumination. There is less contrast and so better for your eyes. Strong contrast for long periods (like watching TV for 4 hours at a time) can contribute to poorer vision.

I don't like glare/reflection on the screen.... I even have the drapes drawn. Thanks for the tips though.

The tv I have has a light sensor where at low light it'll dim.

put the light BEHIND the tv.

well, I just need a light to the left of me, to the right of me, and in between me and the tv and I'd be covered.

Light Bulbs Color Temperature Range - Choosing the Light Bulbs for ...

interesting article, showing a middle "cool white/bright white" category... the "daylight" Phillips LEDs i have aren't what i would call a white light at all, i could call it a very harsh blue... i've had people tell me they almost can't drive anymore because so many people were using LED headlights that looked white to me but the blueishness was like pins in their eyes it appears to have gotten better lately, the soft white LEDs are great, have replaced almost all the bulbs in my house and nearly rid of all those nasty CFLs call poison control

Many of those are cheap halogens with blue tint on them to be impressive. Seldom works. The worst cases are cheap HIDs or LEDs that are plug n play replacements. They are not designed properly for halogen housings and cause awful glare. Properly designed, installed and maintained HIDs, LEDs (or the new lasers) are not so bad and improve visibility for everyone. The cheap crappy ones should be illegal.

Actually, most lights in USA sold cars should be illegal. This country is so arrogant that superior lighting standards that the rest of the world has developed are not allowed in cars sold in this country. Even projector lights were not allowed here until decades after the rest of the world had them.

Yes, the super bright lights are second only to 140dB base speakers in their ability to make one want to choke the life out of the A-hole using them.

But, once again, the manufacturers get arounf the federal regs by using a wavelength or color of light that is not regulated or is a white-ish color that is not deemed illegal.

Sure it blinds us old folks, but do you think those punks using them care?

"Yes, the super bright lights are second only to 140dB base speakers in their ability to make one want to choke the life out of the A-hole using them."

Hey now I resembled that remark for the first decade of my adult life and most of the second going into my third now.

I don't know much about the scripture but somewhere God said, "Go forth and make a joyful noise. so I did! (Haven't really stopped either.)

Besides do you have any idea what kind of electrical, structural and acoustic engineering skills it takes to push that dB levels out of a 1994 Mercury Grand Marquis sedan and have it sound good?

I'm telling ya it's a practical marvel of engineering just to keep the wheels on the ground at that volume!

(Syntax - Sexograph, from their Meccano Mind album. There's some bass to drive around to!)

While your tungsten has the full spectrum. LEDs are (mono)chromatic light sources.

When Trump will be president, he certainly will change that if you ask?

Most white LEDs these days are made from a Blue LED onto which a glop of yellow-emitting phosphor is placed. For 'cooler' LEDs less phosphor is used so that more of the blue light shows through. Conversely, 'warm' LEDs use more phosphor to emit yellow light and have less blue light show through. They are NOT monochromatic.

Here's a graph of a 'cool white' LED spectrum, running from 380 nanometers (blue) to 730 nm (red).

The terms 'warm' and 'cool' come from human experience with nature. The sun looks yellow and makes things warm. Water, the sky, and ice often look blue and generally feel cool compared to the warm sun.

I recall when the first White LED was first developed back in the 90's.... that was a pretty big deal.

Considering they got a Nobel Prize for it.

^{Too bad the Nobel prize lost a some of its luster from who it was awarded to the past 10 years.}

"Too bad the Nobel prize lost a some of its luster from who it was awarded to the past 10 years."

The Nobel Prize you reference was awarded in 2014. Not sure what your point is.

7 October 2014

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2014 to

Isamu Akasaki
Meijo University, Nagoya, Japan and Nagoya University, Japan

Hiroshi Amano
Nagoya University, Japan

and

Shuji Nakamura
University of California, Santa Barbara, CA, USA

"for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources"

"Too bad the Nobel prize lost a some of its luster from who it was awarded to the past 10 years."

No you wouldn't be.

Gore in 2007

Obama in 2009

Like I said, it lost some of its luster.

Well, like I said, The Royal Swedish Academy of Sciences probably isn't politically motivated or prejudiced.

I'd bet they are just plain smarter than most too.

Don't know what they used to pick the recipients... But it's locked up for quite a few years (75 years?) before it's released.

As far as smarter than most, there are a lot of smart people out there that are pretty damn stupid.

In Amsterdam and Brussels the Red districts house warm hookers women.

LEDs are full spectrum and have a smooth graph with no peaks as your graph shows.

Perhaps chromatic as I wrote? You are right.

here i find household LEDs that are called "soft white" and "daylight" which i got a couple daylight ones from Phillips by accident and whoa are they harsh if you have a headcold or prone to migraines you probably don't want to be under those lights.. the soft white are much more yellow and traditionally hued as incandescent.

Visual presentation most people relate something with an orange red color as being warm to touch and something with a blue color as being cool to touch.

Would not reccommend touching to find out if it is true.

Visual presentation?, in my shop where we designed/fabricated stainless process equipment for the food and dairy with a lot of the equipment falling under USDA-3A regulations..

The lights we had in the shop was sodium-vapor lamps. I eventually had to change these out. There were times when we would polish the equipment, deliver it the customer, I then had to send some one over to clean up the discoloring from the welding. Because under the sodium-vapor lamps, it gave a orange hue, the discoloring from welding was basically invisible... until you brought it under a white light, usually at the customer. Until we added an area inside for inspection with different lighting.

Yes visual as they define the light output from warm to cool. It has nothing to do with the Kelvin scale which color temperature is defined.

Sodium-vapor has aways been poor lighting to work under. Mostly was used for outdoor lighting and warehousing. High lumen output for power used. But poor color rendering.

Lighting color falls in the artistic realm, not the scientific or common tradesman ilk of metalworking...

. . . unless yer posting in an engineering forum!

No matter....it is, what it is... You yourself have pointed out that it is not related to metal temperature...I have pointed out that it is related to artistic reference....

Wait a minute, how about that Pilsner or Ale? thread, among many others?

Thousands of TV engineers, lighting engineers, film and camera engineers, and display engineers over the past century would strongly disagree with you. Light can be a fairly exact science and there are a number of scientific and engineering organizations devoted to the science of color.

Those tensors that Einstein used for General Relativity? They use them in color theory as well.

"Light can be a fairly exact science and there are a number of scientific and engineering organizations devoted to the science of color."

Yes, but the definition of what is a 'warm' color and what is a 'cool' color PREDATES the discovery of 'color temperature.'

Wikipedia: Color Theory - Warm vs. Cool Colors

I believe those terms did not originate from science, it originated from marketing.

Not from Marketing, from Fine Arts. We were painting long before we were doing market research.

I think it's interesting that Americans typically prefer "warm" white for living space lighting, while the rest of the world tends to prefer "cool" white.
Quite a reflective topic! Oops! No pun intended.
The warm white color is what you see while trying to read by the fire in the fire place.
Cool white comes from using natural lighting such as sky lights or .... whatever.
This could be another topic for the philosophical section. Oh, that is another blog entirely...

Back to your original question, thermodynamically, as an object gets hotter, the emitted radiation becomes bluer or shorter wavelength, just as you say, opposite to the descriptive adjectives "warmer" and "cooler".

I think the reason cooler is associated with blue and warmer is associated with red is that people associate blue bodies of water (especially in the summertime) as cool and associate red with fire or hot coals.

Just my theory.

I am in India and worked in the field of lighting. I had a learned friend and I had asked him this question about a decade back. His answer was like this.

It is purely psychological and human behavior. In colder countries like Canada, UK and north European countries where room temperatures are lower and is cold inside, people prefer to light fire and keep warm. As against this in India and other countries where it already hot out side, people wish to switch on fan, AC etc and have a cooler atmosphere. The white light which is closer to 6000 K and higher gives that cooler feeling (psychologically) and is hence known as COOL WHITE. The color temp about 5700 K to 6000 is slightly yellowish, may be closer to color of fire. It is still not pure or golden yellow (of sodium vapor lamp) and is hence known as WARM WHITE.

The descriptions come from the common terminology used for colors, particularly for paints and household decorating. Colors in the reds, oranges, and yellows are called "warm," and colors more to the blue and green are called "cool." It has nothing to do with the color "temperature" of the light bulb or LED.

The common LED temp on the warm end that I have seen in the stores here, usually called "soft white," is 2700K. I have found some marked 3000K that are supposed to be "mid-range," but they still tend to the warm. The 5000K LEDs are labeled "daylight" or "bright white." I haven't seen 4000K LEDs here, but wish I could get some. To get good color rendition in our bathroom, I have the luminaire populated with two 2700K LEDs and two 5000K. It looks kind of funny in the luminaire, but the light in the room is a better balance.

Just remember, that the color temperature is pretty much an approximation rather than a hard number. Color Temperature (CT) is only really valid if the spectral content is rather flat. For all lighting products except incandescent, the spectral content tends to have spikes of color and valleys where the spectrum is missing or weak. The effect this causes is color rendering. The apparent color is frequently something that your brain interprets based on the available energy in a spectrum. Consequently, a change in lighting can have a significant effect in the appearance of some colorful object.

What you observe are reflected wavelengths meaning that all of the other wavelengths are absorbed. If, however, the wavelength that you need to reflect is not present in the light source, it will make the objects color different enough to cause a misinterpretation as to the real color. Sometimes the brain fills in the gap but it may be tricked.