A couple of you have written and asked about compensation development using roll film in tanks vs. sheets in trays. The procedure is exactly the same and the results are equally good. Even better is the fact you can do it with the lights on.(posted 8072 days ago)A good starting point would be 1/2 strength developer, using 10 seconds agitation every 3 minutes; increase your development time by double--yes, twice as long. This will yield N-2 to N-3 with most films and developers and it will not reduce EI.
What films work best? I haven't found any film that doesn't work. (A word of caution for those using "old" style emulsions such as Bergger or Forte: I have not tested those films, so I do not know how they would respond to long exposures, either by film speed loss or contrast buildup.) Mostly I use HP5+, Delta 100, TMX and Acros in 4x5, but I've also used it with Delta 400, as well as those afore mentioned films, in 35mm tanks. Acros has become my first choice both for its tonality and its freedom from reciprocity failure (no compensation up to 2 minutes, then 1/2 stop compensation thereafter) and total lack of contrast increase with long exposures.