Color Temperature Confusion

[jwcane.enw]

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Would appreciate some help with fundamental concept of color temperature. I have done a lot of reading and am now somewhat confused. In the Adobe Camera Raw interface the color temperature slider moves from low (2,000 Kelvins, rendering things more bluish) to high temperatures (50,000 Kelvins, rendering things more reddish-yellowish). On the other hand, the CIE UCS Chromaticity Diagram shows the red color as we would expect, at about 2,000 K, and as color temperature increases, the colors reach white at about 5,800 K, and go on to light blue at 10,000 to 50,000 K.

 

A copy of the CIE-UCS diagram is at handprint : color temperature, about 1/3 down the page.

 

I would appreciate some help (maybe a pointer) in reconciling these opposite trends in color as temperature increases.

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[Overgaard]

In the "old" days one used color filters to adjust color temperature. So a dark blue filter was used to cool down a warm light.

 

So, in a way, adding a high kelvin filter (blue=cool) you bring up the kelvin to around daylight (white).

 

Last year I shot a fashion show at 12000 Kelvin which was very ice blue, almost frozen light. So in order for that to get back down at daylight (white), you have to add warm kelvin.

 

You see how you drag down cool light in the top of Kelvin down with using a low kelvin, an opposite.

[Overgaard]

The link you are providing has very little to do with color temperature. But painting.

 

You know, you can paint a wall cool white or warm white. It's basically a pure white where you add either a little blue (cool) or a little yellow/red (warm).

 

The main effect of this is what the color wheel in the article is to describe, which is contrast and harmony.

 

Say you have nice blue painted doors and a green-blue sofa in a room. You then find some white paint for the walls in the basement and it just doesn't look good. You find out the white paint was "breaked" with yellow, and that's why. The "warm" white make the cool colors look dirty.

 

No harmony.

 

To get harmony you need a white with blue added.

 

There's lots of tricks and philosophy in painting, and that's one of them. Basically a "warm" white is a tinted yellow; a yellow paint with so much white added it's almost white. But it's warm.

 

If you look at the color wheel, you can almost see how each color section the the wheel has it's own kelvin; there's cool and warm red, cool and warm blue, in some fashion.

[jaapv]

Also you must consider that on your monitor you are looking at coloured light generated by the monitor whereas a painting or print consists of reflected light. That is the difference between additive or subtractive colour forming, which works in opposite ways.

 

 

It is slightly OT in regard to your original question, because it goes into colour theory and colour managment, but http://www.colormanagement.nl/site/index.php?cms2_intl might be helpful.

[dorman]

To answer the original question, what you are seeing in ACR is the picture you have got being compensated for the colour temperature of the light source.

For example if the picture was taken with a light source of 5000K, then you adjust the temperature in ACR to 6000K, ACR will assume that there was more blue in the light source and reduce the blue in the picture to compensate, ie the picture will look warmer.

 

Hope that helps.