In color printing, the set of filters that you dial in the color head of the enlarger. A filterpack has a base component that deals with the intrinsic "color" of the film (for example, most color negative film is a rather disgusting shade of orange), and a component specific to the particular negative (or color slide) that you happen to be printing.
In color printing, one uses filters in these three colors: magenta, yellow and cyan. The trick to determining a good filterpack rapidly is

  • Use the viewing filters, especially if you are a beginner
  • Remember that what you add in the filterpack is taken away from the print. For example, suppose you have a print with a repulsive yellowish dominant; this means that your filterpack does not contain enough yellow.
  • Remember that usually you get only one color right, and the rest falls where it may.
  • some negatives suffer from color shift, and they just can't be printed "right". Be creative.

Also, notice that you can use a colorimeter, but it is quite tricky. And of course, you don't really need a color head - if you are into masochism you can manage quite nicely with little gelatine filters