Color Temperature 101: discuss

H

Homunculus

Carbonite Member
hello everyone. Can we please discuss color temperature here for myself and other newbies interested in knowing how to properly gel a scene.

Links to free resources would be appreciated but also if you have the time please explain as best you can how to deal with color temperature in film.

Most notably, what's the difference between CTB and CTO. I know one of them converts tungsten to daylight but I can't remember which. Which one do you use outside which one do you use indoors?

If I'm shooting an indoor scene, how do I make sure everything is at a similar temperature, or should it not be? Should indoors scenes be warm or cool?
I know what those terms mean at least, warm is yellowish, reddish and is in the lower end of the spectrum like 2000-4000k or so (I think). Cool color temperature I believe is whitish, blueish and is higher like 5000k+. Right?

Thanks
 
If you've read that link is there something specific you don't understand?

CTO warms things up and lowers the color temp
CTB cools things off and raises the color temp.

There is no hard rule as to what a scene should be. That's dictated by the story and the look you want for it.
 
Agreed. You still have to understand the rules to know how to break them though!

I'm watching the Dark Knight and just saw a good example, indoor Tungsten mixed with some sort of natural daylight or HMI mix
 

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wow ok thanks didn't know that. that's why I asked you guys because you give the practical experience that a site like wiki can't ever have.

so let's say I have a very cool color temp light and I have a bedroom scene that I want to use this light (let's say 1k of some sort) to act as the sun coming in through the window, should I place a CTO on it to give the warm sun look?
 
Homunculus said:
that's why I asked you guys because you give the practical experience that a site like wiki can't ever have.
Click to expand...
It talks about mixing color temps in the wiki article under the section "Artistic application via control of color temperature." One thing I will say is that a little bit of color temp difference can have a big result.

Homunculus said:
so let's say I have a very cool color temp light and I have a bedroom scene that I want to use this light (let's say 1k of some sort) to act as the sun coming in through the window, should I place a CTO on it to give the warm sun look?
Click to expand...

I don't know of any 1k cool light, But if you did have one and you wanted it to be warm in your scene you could just white balance higher than the color temp of your light and it will appear warm. You can also put cto on it to warm it up.
 
There's more to color temperature than just CTO and CTB gels.

First off, recognize the full spectrum. For example, tungsten lights for film are 3200K but the average household bulb is around 2800K-3000K. Fluorescent lights found in most offices are around 4300K and are considered green. They make "minus green" gels to bring them to a more controlled color. Daylight film lights are balanced to 5600K but daylight itself can vary from 5000K-6500K depending on sun level and cloud level.

Now for gels, you need to know that a full CTB or CTO gel will cut your light intensity in about half. That means your 1k light becomes about 500w. That's why it is good to also have daylight balanced lights in your kit as well, such as fluorescents, HMIs, etc.

Hope that helps.
 
NextWaveG said:
Now for gels, you need to know that a full CTB or CTO gel will cut your light intensity in about half.
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CTO cuts the light intensity by about 2/3 of a stop, so a little less than half.

CTB cuts the light intensity by almost two full stops. So down to 1/4 the output. A 1000w tungsten fixture, with CTB on it, acts like about a 250w-300w daylight-colored fixture.
 
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