I would never use split grade printing when the negative is low in contrast, IMO that is the route to dull muddy prints. When the negative lacks contrast any use of soft filtration, ie grade 0, cannot possibly help achieve either separation or contrast. When I have to print such a negative I generally start with grade 4 and if necessary move to grade 5.
Originally Posted by chrisl
10 years ago when I started to use VC paper I very quickly realised that negative contrast is the key to split grade printing. After carrying out tests on contrast levels I very quickly got to the point of exposing and processing negatives that are very high in contrast and suit the method of using grade 0 and grade 5 only. My view of why split grade printing works is that the negative acts as a mask and where the negative is dense (the highlight) it blocks the hard (grade 5) filtration. Consequently, the first exposure with soft filtration is used to control the tonality in the highlight and the second exposure with hard filtration adds contrast and separation in both mid tones and shadows but has little effect on the highlights. Having said that, all highlights have small dark areas where the negative is less dense allowing some hard fitration exposure that introduces a change in the micro contrast of the highlight and consequently enhances detail and texture.
I use the RH Designs fStop Pro Timer but not in the split grade printing mode. I use the two channels, one for soft filtration and the second for hard fitration. I also use it at 1/6th stop increments and when fine tuning use the 1 /24th stop setting, sometimes I work to 1 or 2/10ths of 1 second in my exposures to achieve the exact tonality in the highlight that I require. In the many split grade printing workshops that I have taught the most frequent problem that I see is that the exposure given with soft filtration is far too long. I always encourage my students to print the highlight using the soft filtration to a tone just above paper base white and they find that when the hard filtration is added the highlight will "sing".