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 considerations should be made for varying film types?
Agitation has tan effect on the evenness the chemicals are spread over the surface of the film. If you agitate to little your results might show streaks or bromide run downs (Bromidabläufe). If you agitate to much you first of all have an effect on your development time which decreases. The effect on grain and other pirctorial results is small with one exemption: The activity on the toe of the curve in relation to the activity on the top of the curve. With intermittant periods of non repleneshing the developer locally on the surface of the film you can lift the shaddows by not blocking the highlights.
The longer these intervals last the stronger the effect. Stand development is the strongest and it works especially well with highly diluted one shot developers which in the same time last and don´t die within a few minutes (e.g. Rodinal).
So how does it work? If a highly diluted developer is working on a surface area of the film where the film was exposed a lot and it finds many developable silver halides (exposed silver halides) it locally exhausts itself and weakens to go on (these are your highlights e.g. white clouds in the sky). So these areas are developed slower than if you were to constantly replenish this area with fresh developer through agitation.
In the shados you have the opposite effect (little silver halides have gotten enough light to be developable but if you try long enough you catch them all). This lifts your shaddows and thus efectively increases the speed of your film. The rule of thumb is: Expose to the shaddows and develop to the hightlights. This means you have to stop your development before your highlights start blocking and adjust exposure in a way that your shadows show details. Stand development helps you to lift these thus you can expose less.
We find this effect to give about 1/3rd to half a stop if you compare continuous agitation with the tilt method where you let it stand for 50 seconds and then agitate 10 seconds of each minute.
With Rodinal and stand development this effect can increase speed by a full stop.
There are myths that it can even be as much as two stops or more but we never verified this scientifically.
