thanks for the replies guys

I know there's a bit of trial and error
but was a bit confused as to why the various online formula and calculators
give quite different results
as my pinhole to film is fixed in this instance
I have ordered a collection of sizes and will see what works best
I can't discuss the actual job but I'm sure you will all be interested
when it's been signed off
it's almost as crazy as the guy who did a wet plate stop Frame animation

Ralph thanks for the offer I have emailed you

Ken re. lighting

I'm very fortunate to have over 60'000 j of lighting
mostly made buy the English company Strobe
I have 2 of their swimming pool lights that have 4x 5' 5000j flash tubes on them
and various other 10'000j and 5000j lights
I have only got 14'000j of flash packs to power them up with but I can borrow more if I need it

we have run tests with tri x which came out great but a bit soft hence the initial question
and portra 400 which came out very contrasty with odd colour and is clearly well under exposed
and soft which I guess is down to the pinhole separating the wave lengths of different colours
vs tri-x general ability to cope with everything
we are testing again today so will use a lot more light as it's colour that we will ultimately be using
probably kodak vision3 500t which has similar properties to the portra 400