Thanks a lot guys, Is white balancing something of the digital world? Or did they use to always have to do it like back in the 20's and stuff
The color temperature of light has always been a consideration. However, it was less of a concern in the 20's, since the only option was B&W.
But even then there were concerns about how film captured different colors. The early film stocks were more sensitive to blue, which caused blue objects to look white. For instance the eyes of blue-eyed actors tended to look unnaturally light.
This issue was addressed with the introduction of panchromatic film, but even that wasn't perfect. For instance, Harpo Marx looks like he's wearing a blonde wig, but in fact it was bright red. (Which was why most of his character's names referenced red in some way, like Pinky or Tomaso.)
With the introduction of color film, the color temperature of the light became a much bigger issue. Most film stock is daylight balanced, or balanced toward the blue end of the spectrum. There is also tungsten balanced film, balanced toward the red end of the spectrum. I'm not sure how often that was used, though.
Since the color temperature response of film is essentially set in stone, the light itself has to be manipulated in some way to correct any issues. Most professional lighting equipment was and continues to be daylight balanced. So in controlled conditions, no correction is necessary.
However in uncontrolled conditions, or when a specific effect is needed, the color temperature must be adjusted. This can be done with filters on the lens, but it is most often done with gels on the lights. Which gave rise to various gel ranges, such as CTO, CTB and minus green.