PMK Pyro N-1, N-2 dev times

[cuff]

Hi guys,
First time poster here. This forum is a fantastic resource, so thank you to all who contribute.

I've done a lot of searching, but haven't found the exact answer I'm after -

I'm using Bergger PMK Pryo for the first time to tray develop FP4+ 4x5, shot at EI125.
I'm unsure what my N, N-1 and N-2 times should be.

The Bergger instructions lists N as 12min at 21C/70F, but that's for EI160.
Massive Dev Chart says 10min at 20C for EI125.

As I understand it, it should be around 10-15% change for N-1, so as a starting point would this sound reasonable? -
(20C
)

N: 10:00
N-1: 9:00
N-2: 8:00

Any help is appreciated.

[David Schaller]

Of course you should do your own testing. You can do speed testing and establish your N and N minuses with roll film to save money. That said, those times look close. But don’t start with critical exposures.

[Drew Wiley]

At 20C in trays, my own PMK times for FP4+ are: N-1 = 8 min; N = 10 min; N+1 = 12 min. I rarely do N-2, but if I did, I'd probably use 7 min. It should be noted that I often expose this film as ASA50, though it's just fine for moderate contrast scene exposed at ASA100 processed in the same batch (same times). Minus exposure should be given a bit more exposure in contrasty cases. I never shoot it at 160 - too much risk of underexposed deep shadows. There was also a "Pyro-plus" product designed for faster film speed that was a somewhat different formula, and that might be the cause of confusion. I prefer standard PMK.

[cuff]

Thank you guys. Much appreciated. I've now gotten my head around the film speed and N/N+1/etc. testing procedures and am currently working through that. Getting a bit ahead of myself it seems.