A new method of 'diffusing'

I've sometimes been printing when part way through a series of exposures, or dodging and burning I've, without realising it, knocked either the negative carrier, the enlarger head or the baseboard slightly so that the image has shifted slightly - maybe by just a fraction of a millimeter.

I've nearly always discarded the resulting print and done the print again correctly. But my initial responses to these prints, before I looked at them closely, has often been that they have a peculiar beauty in the affected parts. What you get is a kind of double image - one of the images may be darker or at a different contrast to the other, but one doesn't notice this at first.

The affected part looks diffused but also has a sense of movement within it as if the grain were moving. There is a kind of 3D affect also and the tonal structure can seem richer than otherwise.

This technique is a new discovery for me and I haven't found a way of systematising it yet - today I just nudged the base board before I burnt in a face at a lower contrast. I'll investigate this technique further. I'd like to find a way of shifting the image in a controlled direction and by a controlled amount.

 

 
 
     
 
 

The Inverse Square Law doesn't work - (A startling discovery. Must be read by any darkroom practitioner.)

I've often heard experienced printers say that when using the inverse-square law to make a larger print that one needs to print a grade or so harder in order to get the same 'look' as in the smaller print.

When I tried making a 4x5" print from a 16x20" print using the inverse-square law I soon realised something wasn't working right. What should have been a 'zoney', full-toned print was so overexposed that it was just a black rectangle.

After having thoroughly checked for the usual printer's mistakes, and after having made several more attempts - all with the similar results - I started asking my photographer colleagues about this. Suggestions included reciprocity failure, lens aberrations & faulty calculations.

Eventually I posted a question on the google darkroom group. The answer came back that the inverse-square law only applied to a simple light-source (such as a light bulb). Things get more complicated when one places a lens in the light path.

I don't quite understand the science (it's something to do with the effective f-stop changing), but here's the formula to use:

T = t x (M+1/m+1)²

T - exposure time for new prints
t - exposure time for old print
M - magnification of new print
m - magnification of old print

Magnification (M & m) can be calculated by dividing the length of a side of the image on the enlarging easel with the length of the corresponding side on the negative.

Try it - it really works - you get exactly the same print - no need for adjusting grades.


 
 
 
 
 

Pre-development Bleaching

Pre-development bleaching (or 'contrawise bleaching') allows one to bleach in such a manner that the shadows are affected first and the highlights last. The process uses very dilute ferricyanide after the paper has been exposed and before it enters the developer. Effectively it bleaches the latent image. Working at a high grade one can get the requisite contrast and strength in highlights without the blacks' blocking up' and becoming over-dominant as they often do.

Similar results can be obtained using Ammonium Persulphate reducer, which attacks the densest part of a print more actively than the highlights, and gives an over-all contrast reduction by preferentially bringing the shadow values down . The disadvantages of using ammonium persulphate is that it produces a colour shift, that the shadow areas of the prints start to look 'underdeveloped' and that it is a somewhat temperamental and unpredictable.

However with predevelopment bleaching there is no colour shift and the shadows look fully developed.

Here's how it's done:

  • Prepare about 100ml of 0.1% solution of Ferricyanide. This will be your working stock solution.
  • Add 10ml of the above to 990 ml of water at 20° to make up a litre of working solution.
  • Expose the print.
  • Agitate the exposed print continuously for 1-3 minutes in a tray of the above working solution.
  • Briefly rinse the print.
  • Develop, stop and fix as normal
  • NB:- use fresh working solution for each print!

The proportions of the working solution can be varied from 5-100ml per litre. Obviously the more ferri - the stronger the effect.

Experiment with test strips for different exposure times. Also experiment with different times in the ferri bath: the longer the print is in the bleach the more softening the shadows will receive; eventually the mid-tones start to be affected and finally the highlights.

It's possible, with sufficient bleaching, to get a Grade0 look from a Grade5 exposure - however there will be subtle differences in tonal structure which make this technique very interesting and useful.

 
 
 
 
 

Printing the Life-cast Self portraits

The printing goes through 3 stages. Each stage can take several days to complete:

1 – many small prints (image 12½ x 10 cm onto 7 x 5 inch paper). In which I experiment with different contrasts, exposure times and length of time in the bleach.

2 –medium sized prints where I start to ‘distil' what I discovered in the first stage. I'll experiment also with some dodging, burning in , split grading etc at this stage.

3 – full-sized final prints (image 400 x 320 cm onto 16 x 20 inch paper) Again I take the information I learned from the results of the previous stage and work to produce the final full sized prints through the same process of experimentation.

The bath used for reduction comes from two stock solutions : 0.4% potassium permanganate, and 10% sulphuric acid. Generally I use 200ml of the potassium permanganate with 20ml of the sulphuric acid made up to one litre.

Each of the above stages follows the same sequence:

  • Exposing the paper (fibre based)
  • Develop, stop and two-bath fixing
  • Wash for 10 minutes
  • Hypo-clearing (ammonia + hydrogen peroxide solution) followed by wash
  • Approx 10 second immersion in 1+9 selenium toner followed by wash.
  • a quick squeegee dry and Bleaching
  • Print cleared in sodium sulphite solution.
  • Extended wash
  • Drying

I plan the images to come out of the developer darker than I want the final result as the bleach will considerably lighten them.

The 10 second immersion in the selenium ‘fixes' the brightest high-lights in the print which would rapidly be bleached out otherwise, and stops the print becoming ‘scrubby'.

The bleach is quite opaque. I usually bleach under a blue daylight bulb. This pierces through this opaqueness a little better than a normal bulb.

The print and the bath can either be kept immobile, or agitated in various ways. Rubbing and/or dabbing the print can increase the mottling by, I think, heating up parts of the print and speeding up the bleaching in those parts.

The prints need to be removed rapidly for inspection as the process progresses. The print can be replaced, or rinsed before being replaced – this affects the results.

The prints are stained quite dark by the process making it a little tricky to evaluate.

When the print is ready I rinse the print and leave it in the sulphite solution – this clears the print rapidly.