When using highly diluted developers, the usual advice is to use a generous amount to ensure that you get the effect of dilution and not exhaustion.

However, many people report that you can get away with using less than is often recommended. If the developer becomes exhausted, one result would be less contrast which might be one of the things that you're looking for.

Am I correct in surmising that another effect of ddilute developer exhaustion (of the whole lot, not just local exhaustion which is the aim of this technique) would be poorer shadow density, not able to be compensated for by longer development?

My reason for asking is that I'm experimenting with Pyrocat-HD at half strength for minimal agitation use. I'm very encouraged by initial prints. But I did use 1Litre per 80sq.in (5+5+1000) which is probably excessive. It's certainly a bit inconvenient.

Sandy has stated that 200mL of standard (2+2+200) is the recommended minimum quantity. Half strength of that quantity of developer would be 400mL. Would that be enough to prevent developer exhaustion? (Leaving aside issues of actually covering the film)