Donald is talking about film base+fog. That is the clear or nearly clear part of the negs. You need a densitometer to read it. Basic zone system talk. IF you minus out the fb+f then the density that is at zone VIII should be 1.2 to 1.3. That is a good development time for enlargements with diffusion heads. Typically, cold lights and color heads are diffusion type heads. NOt everyone uses these heads. For some reason, the others prefer condenser heads. The zone VIII density will have to be lower to compensate for some weirdness that condensers cause. It ain't too hard but not coming from a photo background, you will have to swim upstream for a while as fast as you can.

BTW, is 133 lpi enough screen for your artists? Are they doing their own printing? Are these negs used for plate making and then the plates are hung on your offset presses? Inquiring minds want to know.