Gast
What are the implications of using different film development processes, such as stand development versus traditional agitation methods, on the final image quality in black-and-white photography? Specifically, how do these methods affect grain structure, tonal range and shadow detail, and what factors should be taken into account for different types of film?
MirkoBoeddecker
Agitation has an effect on the evenness with which the chemicals are distributed across the surface of the film. If you agitate too little, your results may show streaks or bromide runs. If you agitate too much, the first effect is on your development time, which decreases. The effect on grain and other pictorial results is minimal, with one exception: the activity at the toe of the curve in relation to the activity at the top of the curve. By intermittently refraining from replenishing the developer locally on the surface of the film, you can lift the shadows without blocking the highlights.
The longer these intervals last, the stronger the effect. Stand development is the most effective and works particularly well with highly diluted one-shot developers which, at the same time, last and do not lose their potency within a few minutes (e.g. Rodinal).
So how does it work? If a highly diluted developer is acting on a surface area of the film where the film has been heavily exposed and it encounters many developable silver halides (exposed silver halides), it becomes locally depleted and loses its ability to continue (these are your highlights, e.g. white clouds in the sky). Consequently, these areas are developed more slowly than if you were to constantly replenish this area with fresh developer through agitation.
In the shadows, the opposite effect occurs (few silver halides have received enough light to be developable, but if you leave it long enough, you’ll catch them all). This lifts your shadows and thus effectively increases the speed of your film. The rule of thumb is: Expose to the shadows and develop to the highlights. This means you have to stop development before your highlights start to block out and adjust exposure so that your shadows show detail. Stand development helps to lift these, allowing you to use a lower exposure.
We find this effect provides a gain of about one-third to half a stop when comparing continuous agitation with the tilt method, where you let the film stand for 50 seconds and then agitate for 10 seconds every minute.
With Rodinal and stand development, this effect can increase speed by a full stop.
There are claims that it can even be as much as two stops or more, but we have never verified this scientifically.
