I do nothing but split filtration, almost all are contact prints. I have been using split filtration since the mid-80's when Fred Picker described his process with his Iceland negatives.
Originally Posted by gma
Because Fred always started with the high contrast filter, I do too. I find it easy to arrive at "black" at the edges (B+F) or if there is a point on the print where I want "black." This is arrived at using f8 and step exposures to lock down the first exposure with the 5+ filter. After you are happy with the low tones, you need to analyze your vision of the finished print--will it be high key, low key, rich in the middle? Is the negative thin, hard, or contrasty in spots?
Assuming a middle of the road for your first few attempts, and negatives that were carefully made, expose first with the 5+ at your determined exposure, then close the lens down 2 stops and change to the 0 or 00 filter.
Again do a step exposure for the highlights (remember dry-down effect). Choose an exposure that works and make a work print from the two exposures you have determined.
As mentioned, local contrast and local tonal control are possible with burning or dodging with either filter.
I have found it much easier to start with the low values and then fill in for the highlights, rather that getting the highlights, then trying to find proper low values. This was Fred's rationale, as well.
High contrast negatives will need only one stop reduction between 5+ and 0, and low contrast negatives will sometimes need 3 or even 4 stops down from the 5+ exposure.
Try it. You'll like it.