Selective EI for Diafine

I am a newbie to the world of Diafine, having just acquired the developer. I have read that Diafine works well in high contrast situations when the film is rated at Diafine speed and for low contrast situations you can rate the film at your normal box speed or EI to make up for the lack of contrast. I am confused by this, does rating the film at different speeds for different situations work with Diafine? I know nothing about the realm of two bath developers so I am clueless, though it seems logical.

Any information on Diafine in general, or your methods is much appreciated.

Diafine is a somewhat low contrast developer. This can work well for those living in a hybrid world.

You are correct that you vary contrast with Diafine by varying your EI.

It does depend somewhat on which film you use, as some films seem to work better than others (like with any developer). TriX (in 120) works well for me at EI1000, Neopan 400 @ 650 and FP4 @ 250. I stick to the same EI throughout the roll - it is easier to add contrast later than take it away. The best thing though is to experiment with a roll yourself. Pick a couple of scenes, one high contrast & one low contrast, and shoot them at varying EIs, and see what works best for you.

Do keep in mind that despite its keeping qualities, it does go bad. And when it does, it will go bad with little warning. Both of mine have died pretty quickly in NZ (within a year), while the first one lasted a couple of years when I lived in Holland. Maybe there is something in the water here it doesn't like.