Guillermo, Will the equation change with different types of film? 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?
Thanks Jason Russell WISH-TV Indianapolis, IN "If you go any faster we're gonna travel back through time." ----- Original Message ----- From: "Guillermo" <pen...@rogers.com> To: <pinhole-discussion@p at ???????> Sent: Monday, October 28, 2002 6:43 PM Subject: Re: [pinhole-discussion] Polaroid Reciprocity > > ----- Original Message ----- > From: "Jason Russell" <jruss...@wishtv.com> > > > I was wondering if anyone could help me with Polaroid Reciprocity. I just > > recently started shooting with a Santa Barbara (2 inch Super Wide) with a > > Polaroid back. Right now I'm shooting with Polapan 400 B&W (72). I've > done > > most of my shooting outside and the exposures have all been less than six > > seconds. I wanted to try shooting inside under much lower light. I'm > just > > not sure how much I need to compensate for reciprocity. I checked out the > > info on Polaroid's site, but I'm still a unclear. > > Has anyone else shot with this film or a similar film that could give me > an > > idea of how much time to add. > > The shot I want to shoot right now, by my calculations is about 2 and a > half > > minutes without compensating for reciprocity. > > Jason: > > I have not used the film, nevertheless here is my suggestion: > > Short answer: for indicated 2.5 minutes you should give 17 minutes 3 secs. > > Long answer: As you can see on the Reciprocity Performance chart, the > effective film speed decreases (as expected) as the indicated exposure time > increases, the exposure adjustment column tells you how many stops you > should increase the indicated time. For 4 secs, for instance, the exposure > adustment is 1 stop, that means you should double the time to 8secs. I made > some math calculations (best curve fit) and they predict that when the > indicated exposure time is 150secs (2.5minutes), the effective film speed > will be ISO-58.6, which in turn will need an exposure adjustment of 2.77 > stops, for a total of 1023secs or 17 minutes 4 secs (150 x 2^2.77 = 1023). > If you want some other times, use the following formula: > > T = corrected time > I = indicated time > * = multiplication sign > > T = ( 0.021 * I * I ) + ( 3.708 * I ) - 4.89 > > CAVEAT: the above suggestion is just an educated starting point based on the > Polaroid published information, YMMV. > > Guillermo > > > > _______________________________________________ > Post to the list as PLAIN TEXT only - no HTML > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??????? > unsubscribe or change your account at > http://www.???????/discussion/ >
