Gels and filters, how it's made?

Here is an intersting video showing how gels or filters are made especially for movies I find it more setting up lights at night is very important especially setting it for the mood instead of just using the natural lights especially having all the light source to be same is boring. Also you can change the colors of the walls if they are all white to another color. But also interesting have everything colored white the person is not. Check out the video below how it is made.

Also lens filters are handy to lower the lighting without changing the shutter speeds especially if you are hitting around 1/100 you get shocky images, which is an interesting effect for certain shots but not for normal stuff.