Efke IR820 has it in spades. Hurrell's film clearly had it. Older TXP apparently somewhat had it; current TXP in sheets may or may not still do it depending on who you ask. Is there a film I can buy (I haven't tried R100/PL100 but the published curve is a lot straighter than for IR820) or processing technique that I can use to get a fairly long toe with a dramatic upsweep in the middle of the HD curve? I've tried (semi-)stand development in Rodinal 1+100 and found that it gives the long toe but I also found that the compensation effect introduces significant shoulder so the highlights look quite dead. I want the curve to shoot up steeply as it goes through Zones VII-IX at least, without any apparently shouldering. I can fake it easily by scanning, but obviously want to be able to do it with an all-analogue process.