# Why is Kelvin color temp on digital cameras the opposite of what it is in actuality?



## ak_ (Aug 19, 2015)

This has always baffled me: we know that low kelvin temperatures (eg 3000) look warm, and high kelvin values (eg 7000) look cool right?

So why on cameras are they reversed, and if you dial-in say 3000k the picture is made cooler?


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## ak_ (Aug 19, 2015)

..I'm not asking 'why is kelvin warm/cold the way it is' - i know its based on the color of a flame where blue is hotter than orange/red. I'm asking why on digital cameras is an input value of say 3000 actually making the image look cooler rather than warmer?


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## chuasam (Aug 19, 2015)

Because setting it at 3000°K cools the image so that a warm image looks cooler.


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## ak_ (Aug 19, 2015)

chuasam said:


> Because setting it at 3000°K cools the image so that a warm image looks cooler.


A warm image is already at say 3000k and also cool is much higher kelvin (say 7000 or higher). If i want to cool the temperature I would dial in a higher value (raise the kelvin) not a lower (warmer) value. I'm trying right now (and have on various cameras before). My WB is at 4000k. I just raised it 10000k and the live view image has gotten much warmer. That's the opposite of what it should do. To cool it to something that looks real, I've just had to reduce it down back down to 3600k (from 10000). 10000k should be very cool/blue, but it's the opposite.


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## Alexr25 (Aug 19, 2015)

The white balance temperature you dial in is the color temperature of the scene illumination not the color temperature balance that you want in the final image.  The camera manufacturers assumption is that if color temperature is critical to your work you would use a meter to measure the illumination color temperature and dial that value into the camera and that would produce the correct color balance in the final image.


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## atiqursumon (Aug 19, 2015)

I think 7000 is enough


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## DjMeinhardt (Aug 19, 2015)

It's simple. Say you took a picture of a pure white building and the camera estimated the light falling on the building at a high Kelvin of say 7000. As you said, a high Kelvin temp looks "cool," so the camera thought the light was very "cool" and made the building look warmer to compensate. However, if you say the light was ACTUALLY 3000 (by "dialing" in the temp) the software "removes" that compensation and renders the scene as it would look to your eye in 3000 degree light, which would be cooler than it did when it thought the temp was 7000.

Human vision does this automatically (it's called color constancy), in a range of Kelvin. Scenes only look really warm to us when the Kelvin gets very very low (like at sunset). The camera cannot do as good of a job, so the best solution is to tell it what the temp was (e.g., use a gray card). Now, at sunset, you probably would not WANT to dial in the low Kelvin, because it will make white objects look white (i.e., cooler) and not like our eyes see them at sunset (i.e., warm). Balancing the color with a gray card at sunset gives you non-sunset-like results.


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## snowbear (Aug 19, 2015)

Alexr25 said:


> The white balance temperature you dial in is the color temperature of the scene illumination not the color temperature balance that you want in the final image.  The camera manufacturers assumption is that if color temperature is critical to your work you would use a meter to measure the illumination color temperature and dial that value into the camera and that would produce the correct color balance in the final image.



^
This.  The setting is for the scene.

If the scene is 5000K and you set the camera for 3000K, that means the scene is now 2000K cooler (higher) than the white balance - it's going to look cool-shifted.


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## Designer (Aug 19, 2015)

ak_ said:


> So why on cameras are they reversed, and if you dial-in say 3000k the picture is made cooler?


Because your camera is not making the light, you are adjusting the WB to react to the light.  Think of it as something akin to; on a bright sunny day, you put your sunglasses on before you step outside.  So you are setting the WB to counter the color temp of the light before the exposure.  To verify this, set the WB opposite of what you would do to yield a "normal" color rendering and see what happens.  Your camera will record the existing color temperature in the extreme.


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## BananaRepublic (Aug 19, 2015)

OP, the sun is bright e.g. warm, in Kelvin the light (radiation) coming from the Sun, and other similar stars, is about 5500 degrees Kelvin the background radiation temperature of the universe is 3000 ,approx, degrees kelvin. the fella who said the light hitting a building might be 7000 k has no clue what you're actual question was.

There is some backwardness like you said when it comes to cameras WB settings and  actually science, which I don't understand myself but the above is the actual science as far as the universe in concerned.

In General when you ask a question like that or indeed an any sort of open ended question on hear you get a lot of garbage in response bare that in mind.


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## KmH (Aug 19, 2015)

The background radiation color temperature of the universe is 2.7260±0.0013 K, just above absolute zero K.


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## BananaRepublic (Aug 19, 2015)

KmH said:


> The background radiation color temperature of the universe is 2.7260±0.0013 K, just above absolute zero K.



He asked for an answer not some more baffling crap.


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## DjMeinhardt (Aug 19, 2015)

When I first starting shooting raw I had the exact same question, and got it sorted out, so I think I know what the OP was asking. Light comes in different temperatures, and thus changes how a scene appears to a camera. Our eyes/brain adjust for many of these, keeping white things white under different temps (colors) of light. Anyone who ever shot with film knows that using daylight calibrated film indoors (under incandescent light) gave you pictures with a distinct yellow cast, even though the scene did not look yellow to our eyes. By changing the setting in imaging software you can compensate for this. For example, you'll get a yellow cast shooting under incandescent light with the camera set at daylight (5500 K). By changing the setting to 3000, the yellow cast will be removed, giving you a "cooler" image that more accurately reflects the way our eyes see the scene.

Some typical color temperatures are:

1500 K   Candlelight
2680 K   40 W incandescent lamp
3000 K   200 W incandescent lamp
3200 K   Sunrise/sunset
3400 K   Tungsten lamp
3400 K   1 hour from dusk/dawn
5000-4500 K   Xenon lamp/light arc
5500 K   Sunny daylight around noon
5500-5600 K   Electronic photo flash
6500-7500 K   Overcast sky
9000-12000 K   Blue sky


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## Alexr25 (Aug 19, 2015)

BananaRepublic said:


> OP, the sun is bright e.g. warm, in Kelvin the light (radiation) coming from the Sun, and other similar stars, is about 5500 degrees Kelvin the background radiation temperature of the universe is 3000 ,approx, degrees kelvin.


Actually the background temperature of the universe is about 3 degrees Kelvin.



BananaRepublic said:


> the fella who said the light hitting a building might be 7000 k has no clue what you're actual question was.


The color temperature of an overcast sky is about 7000 degrees K so there is nothing improbable in that.



BananaRepublic said:


> In General when you ask a question like that or indeed an any sort of open ended question on hear you get a lot of garbage in response


And finally something we can agree on!


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## WayneF (Aug 19, 2015)

ak_ said:


> This has always baffled me: we know that low kelvin temperatures (eg 3000) look warm, and high kelvin values (eg 7000) look cool right?
> 
> So why on cameras are they reversed, and if you dial-in say 3000k the picture is made cooler?




Everyone is right, it is not reversed, blue is hotter than red.

You are thinking of the artists concept of color, maybe about red fire being hot,  and blue ice and water being cool, but the engineers think of color temperature as incandescent heat, like heating metal, where heating it turns red hot first, then orange and yellow, and then white and blue, etc.  Our Sun for example, around 5000K light, which we call white and midrange. 

http://www.webexhibits.org/causesofcolor/3.html

Interesting (to me) is the color of our flashes (not incandescent, but instead ionized xenon gas, but color temperature is still measured in the incandescent fashion).

Studio monolights simply turn their voltage down to implement lower power level. This lower voltage is less energetic, and becomes cooler,  more red at low power.

Our speedights are always at full voltage, but they implement lower power level by cutting off the flash tube current when the light is sufficient.  This cuts off the final low trailing tail as it fades away, which is the cool red part, therefore the remaining flash used is less red (the hotter full peak).


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## waday (Aug 19, 2015)

Can someone convert these degrees Kelvin to Rankine for me? The US doesn't like the Metric system.


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## WayneF (Aug 19, 2015)

I can't imagine why, but [°R] = [K] × 9 ⁄ 5


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## snowbear (Aug 19, 2015)

I use Fahrenheit.


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## WayneF (Aug 19, 2015)

Anything about color temperature or white balance in cameras uses Kelvin.     Or Mired.

100 degrees K is a big change at the warm end, but is nothing at the cool end.

So the camera internals will use Mired, which is 1000000/K, which has a more consistent color shift numerically.


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## Big Mike (Aug 20, 2015)

ak_ said:


> This has always baffled me: we know that low kelvin temperatures (eg 3000) look warm, and high kelvin values (eg 7000) look cool right?
> 
> So why on cameras are they reversed, and if you dial-in say 3000k the picture is made cooler?



You seem to taking it as an absolute truth that red=warm and blue= cool. 

This is subjective and is primarily only used to describe artwork.  It's colloquial...it's a common use of speech, but it's not formal or scientifically correct. 

Color equalling a temperature, comes to us from black bodies.  A black body emits electromagnetic radiation (which includes the visible light spectrum) based on it's temperature alone.  So in the range of about 1000 to 10000 degrees kelvin, it goes though the spectrum of light from redish to bluish....and that is where we get 'color temperature'.


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## chuasam (Aug 20, 2015)

Meh! I have a colour checker passport that I use to Colour balance in post.


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## Alexr25 (Aug 21, 2015)

chuasam said:


> Meh! I have a colour checker passport that I use to Colour balance in post.


So do I and as I shoot in RAW I leave the colour balance on auto and sort it out in post, but in the days of film before the instant gratification of digital photography if people were doing colour critical work with reversal film then the only way to guarantee correct colour balance was  used a colour temperature meter and mired filters. 
The colour temperature settings in the camera may be handy if you are shooting jpegs but for a RAW shooter colour checker passport and correction in post is the way to go.


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## ak_ (Aug 21, 2015)

Thanks for all the help everyone. I decided to convert all my cat pictures to sepia in the end.


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## WayneF (Aug 21, 2015)

Don't cut off your nose to spite your face.     Color does have considerable virtue.  Learn to control white balance. There's a few ways, but a simple white card is second to none.


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## Derrel (Aug 21, 2015)

The colour temperature settings referenced using The Queen's English are 704 degrees Kelvin HIGHER than the color temperature settings referenced using standard American English. A fact I just made up. Deal with it!


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## Braineack (Aug 22, 2015)

ak_ said:


> So why on cameras are they reversed, and if you dial-in say 3000k the picture is made cooler?



because it's trying to adjust a yellow light to make it white.

you're telling the camera what the WHITE balance is.

if you have yellow lights and you just told the camera that they should be white, what do you expect the end result to be?


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## Solarflare (Aug 22, 2015)

waday said:


> Can someone convert these degrees Kelvin to Rankine for me? The US doesn't like the Metric system.


 1. If you dont want to use modern international units, thats quite frankly your own problem, not that of other people.

2. I can assure you any US scientist will use Kelvin. As will any serious US photographer.




chuasam said:


> Meh! I have a colour checker passport that I use to Colour balance in post.


 Oh that does a lot more than just fixing light source temperature.


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## waday (Aug 22, 2015)

Solarflare said:


> 1. If you dont want to use modern international units, thats quite frankly your own problem, not that of other people.
> 
> 2. I can assure you any US scientist will use Kelvin. As will any serious US photographer.


I guess my humor was a little too dry on that one...

ETA: BTW, I'm an engineer. We use both systems, sometimes simultaneously.


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## ak_ (Aug 22, 2015)

Big Mike said:


> ak_ said:
> 
> 
> > This has always baffled me: we know that low kelvin temperatures (eg 3000) look warm, and high kelvin values (eg 7000) look cool right?
> ...



Well, read the second post in this thread and you'll know I was already aware that blue is hotter than red in terms of Kelvin values. I've never had a problem controlling the white balance of any picture - just curious why it appeared reversed.


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## Designer (Aug 22, 2015)

ak_ said:


> - just curious why it appeared reversed.


So what do you think now?  Did one of us clear it up for you?


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