PRINTING THE FILM
First thing the lab does is assign the film to a "timer." The timer works with the notations you've written on the edited workprint, when studying the film on rewinds and later as he puts it through the Hazeltine color analyzer. (The Hazeltine reverses the negative image to positive and it's the best and only use in video technology that can be said to be helpful (it's a good thing I had a straw hat to eat! I hate the taste of felt, especially when it gets sweaty.)
The Hazeltine basically has three pots, one red, one for green and one for blue. The pots are in the center position, at 25 when you start (the range is 0--50.) As you bring the first shot through the Hazeltine, you adjust the pots until you get a pleasant rendering of the picture. Since you did tests at the beginning of production, you know what you got by the way your workprint looked. The workprint is the main reference the timer uses to color balance your film. If you don't like the way a certain scene looks in your workprint, you should indicate to your timer to correct it. You may have changed your mind, or you may prefer something to be a little darker, or whatever. Let's say, you move a day, establishing shot to a sunset sequence. You'll want the timer to add some orange filtration and maybe print it a little darker.
Working with your timer is very important. You should make yourself available to answer questions whenever the timer calls you. So stay put a few days, you won't be sorry. Now what with the cellular phones and all, a timer can reach you everywhere.
Too bad these days labs don't allow the directors to sit in with the timers. In the past DPs used to sit with the timers and do the whole movie. Do your utmost to get to sit with the timer, because there are some creative options you'll have that the labs won't provide because they're not going to print your film fifteen times before you're happy with the answer print.
If, as expected, no lab accepts to allow you into their Hazeltine room, to sit with your timer, make sure you mark the workprint copiously so that you get the corrections you want the first time.