I always keep forgetting this formula, mostly because I hardly ever use it, but every once in a while I do need it and then it’s tucked away so deeply in my brain I can’t find it. So, for once and for all, here it is:
UnderExposure – Pushing
ISO 100-200 = 1 stop underexposure = 20% increase of Development Time
ISO 100-400 = 2 stop underexposure = 50% increase of Development Time
OverExposure – Pulling
ISO 400-200 = 1 stop overexposure = 10% decrease of Development Time
ISO 400-100 = 2 stop overexposure = 20% decrease of Development Time
For more specific development times and films vs. developers look here:
Digitaltruth
Photography Contrastique - Alternative Photographic Processes 
a good ressource for many developer&films is
http://filmdev.org/
with example pics.
vt
Hey Vern!
Thanx for the tip, I have never seen that site! Am no Flickrerer person so maybe should dive into that one day..and maybe not too 😉
The example photos are really great, they should do that at Digitaltruth as well.
Thanx again!
Indra