Split Grade printing in it’s most basic form is a process whereby two exposures are given, one through a Grade 5 filter and one through a Grade 00 filter. These two exposures can be varied in order to arrive at the correct contrast for almost any negative. I have another, simpler version which i will write about at a later date, but for now I’ll explain this method.
As I said, there are two exposure give, one through a Grade 5 and one through a Grade 00. That is the theory anyway, -but in reality some negatives only need one filter to print. This is especially true with extremely thin negatives which can only be printed on a Grade 5.
Let’s go back to basics: The photographic emulsion in a Variable Contrast or Multigrade paper is made up of two light sensitive layers. One is sensitive to green light and gives a long range of greys from pale white through to dark grey, it won’t give a deep black unless it’s grossly overexposed. The other layer is sensitive to blue light and gives a very high contrast result, consisting of mainly black and white, with very few intermediate tones.
White light gives roughly equal amounts or both green and blue light, so exposing without a filter activates both layers giving a contrast between the two extremes, -roughly grade 2, depending on enlarger type. Using a Grade 2 filter also activates both layers equally, but reduces exposure time because of the density of the filter.
When two different exposures are given, one of the layers is activated more than the other and this moves the contrast away from grade 2.
Because this subject needs a full explanation beyond the space I have here, I have made a demonstration video (in two parts) which should make the point more clearly. Please excuse my slightly wooden presence in the videos, I much prefer to be behind cameras rather than in front of them.
Originally there were a number of shots of me talking to the camera, but these attracted so much ridicule from my students at the University where I teach that I took it down. This is the edited down version separated into two videos. The parts of the film shot under safelight are done on the night shot setting of a basic video camera and this has a slower shutter speed, causing the movement to look a little blurred and delayed. Consequently, the shots of me timing my exposures don’t appear to match up with the sound of the metronome, but in reality they were.
Split Grade Printing Part 1 ? ? http://www.youtube.com/watch?v=5XgmJk2Fmpw
Split Grade Printing Part 2 ? ? http://www.youtube.com/watch?v=p8H7eLcGUZs