How to convert Kelvin temperature?

[olegtov]

Hello all!

In Lightroom 1.2 they changed the colour temperature representation. Before it used to be in degrees kelvin, and now it is from -100 to 100. I'm sure the principle is the same, it's just the way it is displayed that has changed. But here is my question.

I have used a Macbeth colour chart in conjunction with ACR Calibrator to try and profile my camera. It was a success except for one little part. The temperature it gave me was 5000K. Lightroom now displays in -100, 100. How could I make the conversion to properly enter the temperature?

Thanks!

[Richard Marcellus]

I am running Lightroom 1.2 on Windows and my Colour temp slider is still in Kelvin. The Tint setting is -150 to +150. I am not sure why your system is different.

Richard

[olegtov]

My apologies. I have just realized I was editing a jpeg. Now with raw its all fine. I had forgot that I exported those raw files to jpeg, and was editing a jpeg.

Thank you very much!

[Richowens]

Open a Raw file in LR 1.2 and it will display the kelvin scale. A tiff or jpeg has the white balance baked in more or less and is displayed in the + or - manner.

 If I am incorrect perhaps someone can correct me or expand on the subject.

 Rich

[mikeseb]

one degree Kelvin = one degree Celsius.

freezing/boiling points of water are 0 and 100 degrees in both scales.

absolute zero = 0 Kelvin / -473 (I think) Celsius.

[digitaldog]

Considering how inaccurate and old fashion it is to describe white in terms of Kelvin, why?

Many different colors correleate to the same Kelvin value. When you see such values, say to yourself, my mileage will vary. Now move the sliders until you like the color appearance.

The reason the CR calibrator process works is because we compare the RGB values in ProPhoto RGB from CR and LR to the RGB values of the target measured using LAB and converted to ProPhoto RGB scale. Kelvin never enters the picture here.

[Graeme Nattress]

The combination of Kelvin and Tint will define any white point uniquely. The tint being the distance, above or below the plankian locus of the correlated colour temperature of the white point.

[Peter Stacey]

one degree Kelvin = one degree Celsius.

freezing/boiling points of water are 0 and 100 degrees in both scales.

absolute zero = 0 Kelvin / -473 (I think) Celsius.


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As Andrew Rodney said, it's innacurate to talk of white in terms of Kelvin, but since it's still a common usage, I guess it will still be around for a while.

But, on another matter (not really on topic), I might just correct a couple of statements in the above quote (you know, so we don't give our kids some bad advice for a science project or something):

It's true that a degree change is the same amount on both the Kelvin scale and the Celcius scale, however, the freezing and boiling points of water are not the same on both scales.

0 Kelvin = -273.16 deg C

0 deg C (freezing point of water) = 273.16 K

100 deg C (boiling point of water) = 373.16 K

Regards,

Peter

[mikeseb]

But, on another matter (not really on topic), I might just correct a couple of statements in the above quote (you know, so we don't give our kids some bad advice for a science project or something):
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Peter, thanks. It just goes to show you--when you set out to be a wisea--, it helps to have your facts, and your syntax, straight!