1600 works fine with daylight, where you probably don't need 1600 anyway. Under tungsten light 1000 is more realistic with Diafine and Tri-X. 1250 is a decent set and forget compromise.
Originally Posted by ntenny
As others said, it doesn't matter that some A is carried over into B. Just avoid the reverse and don't get any B into the A. This will not happen in normal use, just be sure not to do it mistakenly.
You don't really need to do the "replenishment" thing anyway with Diafine. That's more for a situation where you have a deep tank you keep full. As you use it, dry film will deplete the volume of A solution. I've been happily just pouring it back into a bottle (one bottle each for A and B) and using what I have, for decades. That is, I've been doing this for decades, not with the same Diafine though. It does last a very long time but it will eventually become less active. I used to get about 50-60 rolls of 35mm through a quart. I've been using my current gallon for nearly two years now and it still works fine, but I haven't put that much film through it. I now use it mainly for 35mm Tri-X and 120 Pan F+, occasionally 120 Tri-X when I need the speed but don't need Delta 3200, and mostly use other developers for other needs.
Quarts versus gallons - for most people a quart is fine, but for a while there the gallon size from Freestyle was the same price as quarts elsewhere. Freestyle has gone up while others haven't increased as much so this is no longer true. But it's still cheaper per ounce in gallons, as most things are. Since I've been meaning to use it in my deep tanks with hangers for 4x5, which need 1/2 gallon of solution, it's just as well but if you are only doing roll film or sheets in trays a quart is fine, and plenty to see if you like it.
Fixer - well I prefer rapid fixer for the time savings, the easy mixing, and for the fact I can leave out the hardner, which impedes washing. (If you have pretty warm tap water there in Australia though you should probably use the hardener for film.) I never use hardener for paper, so this lets me use one jug of rapid fix to mix both. But since you are shipping from the US to Australia liquids are going to cost a lot more if they can be shipped at all. Regular powdered fixer like Kodak Fixer or the like will be fine.
Do not use a stop bath with Diafine. I've never actually tried using it since the manufacturer advises against it, so I'm not sure it would cause any problem, but it's definitely not needed. Just rinse in water.