Re: HP5, Delta films and reciprocity

John wrote:

> I use the formula, y=.91x^1.51, where x is the metered time and y is the
> corrected time. It approximates the reciprocity pretty closely, and has
> worked for me for exposures up to 2 hours on FP4+, which shares the same
> reciprocity failure as HP5+. I've always processed normally, with pmk pyro.

This is interesting, a variation on the formula I was given. Where did you
get this formula? I wonder if such formulas exist for all films? Maybe if
I used another factor, like your .91 above, with the Kodak chart, I could
work out a similar formula. I was only looking for an exponent the first
time I tried.

--shannon
Received on Sat Jul 20 10:04:52 2002