----- Original Message ----- From: "Jason Russell" <jruss...@wishtv.com> > > Will the equation change with different types of film?
The equation is just a math model of the reciprocity correction curve, the latter is just a graphic representation of the discrete values, either given by manufactures (like the ones given by Polaroid for the film in question - Polapan type 72) or obtained by us thru experimentation. Since each film has its own reciprocity characteristics, each film would have its own equation. > Or do I just plug > the indicated time into the equation to get a starting point? If it does > change, which numbers will be different and how do I figure them out All the coefficients change. You can find them by doing a Regression analysis of the known reciprocity correction values, I use the Least Square polynomial method, here is a hint on how to do that: http://www.efunda.com/math/leastsquares/lstsqrmdcurve.cfm , for those of us confused by the above, using a program like WinCurveFit http://www.krs.com.au/wcf.html is "a good thing", that is what I used to give you the answer BTW. Guillermo
