Reciprocity How it may affect monochrome film

The use of a Zero pinhole camera means that long exposures are the norm. It might be a good idea to give an insight into how reciprocity affects the negatives. It is a wide-ranging subject that afflicts colour and black and white materials in different ways at long exposures, extremely short exposures and with flash. Because of this I am limiting this post to long exposure times with black and white film.

The Law:

The formula E=IxT expresses reciprocal relationship between the intensity of light reaching the film and the time allowed to act on the film. If one increases the other decreases proportionally, no net change in exposure occurs.

Ansel Adams The Negative.

At long exposures this law breaks down, known as reciprocity failure. It is where a seconds worth of light is not enough to satisfactorily produce the required densities in the negative. So the longer the exposure the greater the compensation needs to be. With these exaggerated times comes a side effect in that the lower values recorded become under exposed more than the higher ones causing the contrast of the negative to increase. You can make adjustment for this when developing the film by a reduction of ten percent for up to ten seconds, from ten seconds by twenty percent and from a hundred seconds by thirty percent. These changes are easy to control for single frame exposure made with large format cameras but a little difficult to achieve with roll film. If all the frames on the film are exposed for no longer than ten seconds then the ten percent reduction will control the increase in contrast across the whole film, but in practice this is not always the case with exposure times being all over the place. I would suggest that a reduction of ten percent be the starting point and that with experimentation will find what works best for you. Having said all this the side effect of higher contrast maybe to your liking in which case where's the problem.

Further reading

The picture included in this post shows a slight increase in contrast. The negatives Ilford FP4+ were processed in PMK Pyro without an adjustment for increased contrast. Printed on grade two multi grade paper developed using Moersch 6 blue.

The following images and those above were all made using a Zero multi format Pinhole camera. The pictures below are from negatives using Fomapan 100 at box speed developed in studional for 11 minutes. scanned from photographs printed on Ilford multigrade 4 developed in souped ilford multigrade. 

Taking the stop out of printing?

An acquaintance recently posted that he was having trouble with his photographs. The prints were producing brown stains on the edges and face of the paper which he had not seen before. He went on to describe a process that does not include stop bath. I have always accepted that stop was essential when printing.

This revelation made me stop and think about all of the books I have read over the years on photograph production. As far as I was aware none of them said that there was a choice. Just to be sure I went back to the reference books on the subject I trust most. After consulting Tim Rudman  Master Printing course, Michael Langford Basic Photography and Ansel Adams The Print - by the way this is the only book to explain what happens when stop is omitted.

Ansel Adams writes: That stop bath is a weak solution of acetic acid that neutralizes the alkalinity in the developer stopping development straight away. Fix being acidic would have the same affect as stop bath but it prevents the contamination of the fix from the alkaline in developer which quickly exhausts the fix making it more likely that the prints will stain.

I should point out that my acquaintance has been producing prints that have not shown any signs of staining till now. It turns out that it was a lack of proper washing before the fix that was causing the problem and not exhausted fix.

The question that keeps coming into my head is why wouldn't you use stop? It makes no sense from my point of view. I spend a lot of time in the darkroom making test prints carefully choosing the right amount of light for exposure. Once in the developer I watch and wait for what I judge to be the right amount of development so I can remove it to the stop, freezing it at that point in the process. If this was substituted for water this would not be the case it would only slow down development making a mockery of all the careful planning gone before and adding a degree of uncertainty as to whether or not it was going to stain.

This is one of the main issues I have with not using stop bath which for me translates to film as well. You spend all that time getting the time, temperature and inversion right, - for what? Because you can not be bothered to use stop?it's to expensive? I will admit to not using stop at one point but not for the reasons given earlier when developing film. I reverted back to stop mainly because I did not like the look of the negatives it was producing. They seemed to have a soft look to them.

I know that this must sound like a bit of a rant and to a certain extent it is. Sometimes it's good to get things off your chest. As far as I'm concerned there are many different paths to creative nirvana and how you reach it is up to you.

Since writing this I have discovered a number of print developers that do not require a stop bath. As long as you use running water in its place for at least thirty seconds. These developers use Amidol in the formula. They can be found in The darkroom cookbook.

You maybe interested in this article on Fixing faults