Lightroom colour temperature

englishpremier · 31 Dec 2013 at 15:45

Is it me or is the colour temperature slider in lightroom the wrong way round?

A higher colour temperature should result in a cooler looking image i.e blue

Yet in lightroom moving the slider to the left, and lowering the temperature results in a cooler image, when it should be warmer.

WTF?

Zogger · 2 Jan 2014 at 13:43

Not an expert, but I think the point is that you are selecting the colour temperature that reflects the lighting of the world as it was pictured, and then the software is adjusting the colour of the image to account for that.

So, if you start at 5000k and it looks too red, you would reduce the colour temperature to say 4500k to indicate that the lighting in the real world had a low colour temperature, and in order to account for that the picture needs to appear bluer.

I guess the point is, colour temperature is an attribute of the scene that you are capturing, not an attribute of the image.
I imagine this is particularly useful if you have a single light source such as a bulb, and you know the exact colour temperature of the bulb - you can input that temperature in to lightroom and I would think it would come out 'white'

Is this not the same as what would happen if you adjusted it in camera (I never do this as I just adjust the raw in lightroom)? Personally I find a higher number resulting in a warmer image to be more intuitive anyway...

Ksanti · 2 Jan 2014 at 14:38

englishpremier said:
lowering the temperature results in a cooler image, when it should be warmer.

Lowering the temperature should be warmer? I don't follow that logic...

englishpremier · 2 Jan 2014 at 15:20

Ksanti said:
Lowering the temperature should be warmer? I don't follow that logic...

Because colour temperature is measured in degrees kelvin. It's basically set by heating up a piece of platinum and noting it's colour at certain temperatures in degrees kelvin.

Red hot would be around 1000k, white hot at 4500-6500k, and blue form 7500k.

Basically you're going from (low temperatures) warm colours i.e red, orange, yellow. To cooler colours (higher temperatures) white, blue.

Lightroom seems to get this the wrong way round, but I think that Zogger's post explains well what lightroom is doing.

For more on colour temperatures (in lights) - http://www.motobulbs.co.uk/2012/04/understanding-motorcycle-bulb-colour-temperature/

Jase · 2 Jan 2014 at 15:43

I don't get what the problem is, lightroom is doing it in a logical way to me, I understand the options it gives me well enough to get the results I want... if there's some physics/math that says it should be the opposite then I'm glad they ignore it

nolimit · 2 Jan 2014 at 16:44

Bit like the flame of a candle theory you learn at school. The hottest is the blue flame and the coolest is the red flame.

D.P. · 2 Jan 2014 at 17:39

englishpremier said:
Because colour temperature is measured in degrees kelvin. It's basically set by heating up a piece of platinum and noting it's colour at certain temperatures in degrees kelvin.

Red hot would be around 1000k, white hot at 4500-6500k, and blue form 7500k.

Basically you're going from (low temperatures) warm colours i.e red, orange, yellow. To cooler colours (higher temperatures) white, blue.

Lightroom seems to get this the wrong way round, but I think that Zogger's post explains well what lightroom is doing.

For more on colour temperatures (in lights) - http://www.motobulbs.co.uk/2012/04/understanding-motorcycle-bulb-colour-temperature/

Spot on, that is why the measurement is in degrees Kelvin, a measure of physical temperature and not some other unit invented for white balance.
But it does make things confusing because when one talks about tone and warmth of a photo/painting/painted wall oranges/red are regarded as warmer and blues colder.

And As zogger says, the WB slider in LR is setting the WB of the scene at capture time, and LR will try to make a colour neutral image with that information. If you know the exact WB value in degrees Kelvin, which you may know in a studio with controlled lighting, then you can simply enter that exact value and you will get a neutral image.

oio · 2 Jan 2014 at 19:52

If an image's apparent colour cast is the difference between the lighting colour temperature that appeared in the scene, and the white balance colour temperature setting, then:

cast temperature = lighting temperature - white balance temperature.

Or to put it another way:

white balance temperature = lighting temperature - cast temperature.

The overall colour temperature of the image is the lighting temperature (absolute value) + the colour cast (relative shift).

So to increase the cast temperature (thereby increasing the overall image temperature, making it bluer) you decrease the white balance temperature. Decrease the cast (yellower image) by increasing the white balance temperature.

As an example, the diagram shows how a scene shot under 5000K-rated lighting looks if you increase or decrease the white balance temperature by 1000K.
After a white balance increase in temperature, the original neutral tones now map to yellower tones: an image colour temperature decrease.
After a white balance decrease in temperature, the original neutral tones now map to bluer tones: an image colour temperature increase.

This is why the Lightroom slider is correct in showing blue to the lower end of the scale, and yellow to the upper end. Think of white balance as a correctional shift, remapping the tones recorded by the camera's sensor. It's the difference between what you recorded, and how you want the image to appear.