contrast control with rotary processing

[Richard Littlewood]

I use a JOBO rotary processor to develop sheet film, and after a little modifying of the spirals I am really happy with the results. I make up ID-11 from raw chemicals and this gives really tonally smooth negatives, not at all dense or contrasty. With subjects of a high contrast it's a brilliant method, but with subjects of a low contrast the negs can be a touch flat, and sometimes difficult to print, especially with semi-matt papers, and more especially with Forte paper. Developing the negs for longer only seems to increase density. Any suggestions as to how ID-11, or D-76 could be chemically tweaked to offer a touch more contrast with continuous development would be welcome. One option is to move out of northern England where the light is often flat - but the landscape is brilliant!

[Bruce Watson]

Developing longer increases density, and contrast index (gamma). For a through explanation of how it works, see Ansel Adams book "The Negative." In it he explains how to determine development times to give both more, and less, contrast.

[Gem Singer]

Hi Richard,

Get hold of a copy of "The Film Developing Cookbook", by S. Anchell and B. Troop. There are several solutions to your problem mentioned in the book. It is worthwhile reading.

[Stan. Laurenson-Batten]

Richard.

I too use a Jobo CPP2 for all processing of all sizes of films.

I used D76/ID11 but changed to the Patterson Aculux2, which seemed to give me a contant contrast/tonal range that was easy to print.

I have used Forte papers when printing misty scenes with good results, but have found that the Forte range can vary in contrast from batch to batch.

I am sure that you could control the contrast in your Jobo using ID11. but feel it would be unwise to mess about with a tried and tested method of constant agitation, speed and time.

Have you tried Kentmere VC or Ilford VC?

[paulr]

other options include:

-higher developer temperature (no real advantages to this one)

-higher developer concentration (will also give a straighter curve, if you happen to be looking for it)

-higher concentration of alkali in the developer (seems to preserve the shape of your curve, and doesn't seem to increase grain as much as increasing development time.

-selenium toning the negative (increases contrast but keeps other aspects of the neg identical. no good if you plan to intensify, etc.)

[Eric Woodbury]

You can increase contrast (in the shadows) by increasing exposure and moving up away from the toe of the film. This works with many films, but if you already have plenty of exposure, then develop longer.

[Kirk Keyes]

"Developing the negs for longer only seems to increase density."

That's an interesting observation, as that is usually the answer to your question. I would suggest looking into the Adams book mentioned by Hogarth, or "Beyond the Zone System" by Phil Davis for a more in-depth treatment.

[paulr]

"Developing the negs for longer only seems to increase density."

I missed this the first time I read the post. Are you sure? I'd suggest testing it a bit more. It would be very unusual if increased development increased density EVENLY over the whole scale. If it worked like that, then you found a magical way to increase your film's speed. Typically what you'd expect is slight increase in density of the shadows (slight speed increase) and significant increase in density in the highlights (significant contrast increase).

[Richard Littlewood]

Thanks for all the interest in this one. I've read The Negative by Ansel Adams and in there he says (with images to back this up) that constant agitation leads to higher contrast. I once tried Agfa Rodinal with Jobo processing of FP 4 and the increase in contrast v intermittent agitation was quite alarming. ID-11 dosnt seem to work this way - it must be a chemical thing. Looking at some processed negs here, I can easily say there is an increase in density from over development for sure, and possibly greater shadow detail, but as for an expected increase in contrast - it isnt there. This is using 700ml of solution - ID-11 1+1 - 12 sheets for 7 mins. Altogether the negs are really smooth, although with a low contrast subject they can sometimes be 'muddy'. Perhaps I'll have to under-expose and over-develop although that goes against the grain a bit.

[Kirk Keyes]

"I've read The Negative by Ansel Adams and in there he says (with images to back this up) that constant agitation leads to higher contrast."

Yes, when compared to development that is not constantly agitated. You can still get lower levels of constrast with continuous agitation - simply use a shorter development time.

Are you using your eye to make these density measurements? Perhaps you should look for access to a densitometer or make one with a spot meter.

Again, I suggest checking into the Davis book I mentioned above.

Kirk

[paulr]

What intermittent agitation does is give your development a slight compensating effect.

In the time the developer is motionless, the developer that's in contact with the surface of the film does not get replenished. So the developer in contact with the highlight areas, which have lots of reduceable silver, gets exhausted very quickly. The amount of silver that it can reduce relative to the total reduceable amount is very small.

In the shadow areas, though, where there's very little reduceable silver, the developer that's sitting there can reduce a larger proportion of the silver before becoming exhausted.

So the shadows are getting proportionally more development than the highlights.

While this can be seen as giving lower contrast, what's significant is that it's altering the shape of the film's curve. It subdues development of the densest highlights while still giving adequate shadow detail. This is a type of film response that's useful in a lot of situations. You can achieve this tonal response at any contrast level by increasing the development time, or by using other methods that have been mentioned.

There are other ways to get a compensating effect. Most of them involve using a weaker developer dilution, or in some cases a developer formula that's specifically designed to give a compensating effect.

[Stan. Laurenson-Batten]

I am in sympathy with PaulR on this.

But what really goes against the grain for me, are those knowledgeable types in the photographic world, that quote the good and the great of historic photography, and see it as the only correct way of doing this and that. Progress is in constant motion- it should be forward.

If one is minded to copy photographic style of yesteryear all well and good, but to my mind it is very rarely the case, but more often the airing of literate knowledge to no advantage or progress.

All very well if the camera, lenses, chemicals, and modus operandi as then used are the same as today. But theyare not by any stretch of the enthusiastic imagination!