How do I know what Kelvin temp the light is?

[DDirector]

Magic Lantern has Kelvin white balance.
I generally use the auto cycle and then adjust it to whatever looks right if needed.

But, is there a way to find out the correct Kelvin temperature of the light? So, if I use lights and if I have to match it to other light sources, they are all the same.

Most of the time the auto mode is not right and I have to adjust it manually, but when I do, I can go through thousands of degrees and it will look the same or so similar I wont see a difference. I want to get the correct settings each time.

 

[Loren Simons]

Depends on what light source is. Tungsten Lights are 3200K, while daylight balanced lights are 5500K. The old tried and true method is to put a white card in front of your camera and adjust it until it's white. They also manufacture different offs of white to give you a warmer or cooler look if you want.

 

[Samuel H]

I use custom WB whenever I can (take picture of white card, set it to be used as custom WB, use custom WB)

if you want to dial your temp in K, you can go by eye, as Loren said, or you could use a light meter

 

[maranfilms]

Once you work around different lights, you will be able to pretty much tell the kelvin temp just by looking at the light. If it's yellowish, you know it's in the 2800-3800 range, if it's blueish then you know your dealing with a light in the 5000-7000 range give er take a few hundred degrees.

I usually use the numbered kelvin temps in the cam. I never use a card. Once you have an idea as to where your at, you can tweak and fine tune it from there by moving the color to where you like it. So if you shoot daylight, then add a little magenta, you will get something a bit different, if this makes sense. (thats an example)

Canon cameras have the best auto white balance I have seen in a cam. So if your shooting Canon, you can put it to auto setting to get an idea of where it should be, then manualy go from there so it doesn't change when you move the cam. This will work till you develop an eye for knowing temps.

Flourescants are whacky, they can have so many different colors, and change with age, I stay away from them. They usualy fall somewhere in the 5000-7000 kelvin range, but I tend to rate them 60 htz. and butt ugly, lol. They can be gel'd to match, but the tubes are a pain to work with.