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Posterisation - traditional darkroom guide

Fun in the darkroom? Here Peter Bargh shows you how to lower the tone to create a posterised print

|  Darkroom Printing
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Words & pictures Peter Bargh

Most black & white photographs consist of a continuous range of tones from dense black through endless shades of grey to pure white. Anyone who's familiar with paper grades will realise that changing the grade alters the tonal range. A hard grade of four or five increases contrast whereas a soft grade of zero or one reduces contrast. But it's also possible to manipulate the image in the darkroom to control the amount of tones in a picture. The end result would be a print with maybe four or five flat non-graduated tones. This technique is called posterisation or, as the method implies, tone separation.

Posterisation is a fairly difficult technique to master but once done gives impressive graphic images. To try the technique you need to make three negatives of different densities and then expose these, in register, on the same sheet of printing paper. Apart from your usual darkroom kit you ll need some lith film, which is available in 35mm bulk lengths or sheets, lith developer, fixer, a tray or tank to process the lith film, some liquid opaque and a spotting brush. You should also use a registration punch to ensure each negative is printed in perfect register, but we saved on costs by using a soft pencil.

This shot of Lee Ford, shows an example of a four tone posterisation comprising black, white and two grey tones. I used this negative to illustrate the technique because of its interesting backround, which suits this type of manipulation.

1 First we need to make a set of three lith positive from the selected negative  one correctly exposed, one under and one over exposed. These will then be used to make the three negatives.
There are two ways to do this. One would be to enlarge the negative onto a sheet of lith film. This will give a large positive to work with, but you then need an enlarger big enough to make a final print from the created sheets. Large format enlargers are hideously expensive and big so a better option is to make a set of contact positives from your negative, which can then be printed using a 35mm or medium-format enlarger. Under a red safelight place the original negative in contact with the lith film. I used a 6x7cm negative, shot on a Mamiya RB 67, so I needed to cut down some 5x4in lith film.

2 You ll need to test the exposure by making a test strip. See the beginners feature this month if you ve never made a test strip before. As a guide set the enlarger to f/11 and try 2, 4, 6, 8,and 10seconds exposures.

3 Develop the test film in the lith developer. It s a good idea to do this in a small tray so you can see what s happening. Fix the developed positive and check which strip gives a normal, but high contrast image. My example was seven seconds. I could also see from the tests strip that four seconds would create a light underexposed result and 10 seconds was about right for the overexposed positive.

4 Process the exposed sheets and dry them. You now have three positives. One with only the deepest shadow areas as black, one with mid tones and shadows as black and one with mostly light tones.

5 When dry check to see that there are no small holes in the black areas. These are created by dust that came in contact with the negative when sandwiched and can be masked out using liquid opaque and a spotting brush.

6 Make a second set of contacts on some more lith film using the same mid exposure from the previous test, in my case seven seconds.

5 Once processed you will have three negatives. Again use the liquid opaque to touch up any more pin hole blemishes on the black areas. Now you are now ready to print them in register on a sheet of printing paper.
Make a test strip using the first negative to find a mid grey.

6 If you had a pin register you would be able to place one negative after another in register and expose using the time found from the test strip. Without this you need to make some soft registration marks on the paper. With the paper in place and the first negative sized up use the red swing filter and switch the enlarger on. Then carefully mark a few points that you will be able to match up when the next negative is placed in the carrier. I used the brim of the model s hat, his knuckles the baseball glove logo and one of the letters to make reference points.

7 Make the first exposure with the red filter out of the way then swing it back, switch negatives and line up the image using the penciled reference points. Repeat this step for the third negative.

8 Process the sheet of paper and you should end up with a posterised image showing a reduced range of tones.



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