Most films publish a chart that gives a good starting point on the reciprocity failure. Richard probably has a better explanation, but let me try. Since the wife has an off brand dishwasher (me and I have some experience in the subject) The grease on a cast iron skillet will largely come off right after the first application of soap, hot water and elbow grease, just as film at short exposures will build density in predictable manner early in the exposure. Yet if you look closer the same amount of soap water and a sponge will not get that stubborn stuff off. It takes more time and usually a switch to an SOS soap pad to scrub it clean. Film once its reach a certain point in the exposure, "fails" to record the light at the same rate and it takes more time (just like the stubborn stuff wouldn't come off without more time) for it to build density that is comparable with the rate density was built early on. Your light meter can't be adjusted for that because its not consistent between film and time. Throw in the fact that the meter only tells you what the exposure needs to be if the subject were 18% gray, and such long exposures often fool meters too. Well best get that dishwasher running again lest the wife decide its time kick the old model to the curb and replace it with a newer, younger, and more capable model. --- On Thu, 11/20/08, Rich Mason <cameratraveler@xxxxxxx> wrote: > From: Rich Mason <cameratraveler@xxxxxxx> > Subject: Re: Long digital exposures? > To: "List for Photo/Imaging Educators - Professionals - Students" <photoforum@xxxxxxxxxxxxxxxxxx> > Date: Thursday, November 20, 2008, 10:21 PM > Yeah, reciprocity failure is one reason I rarely bothered > with long exposures on film. It required either > experimentation or consulting of a chart for the specific > film to determine the correct exposure. What a meter would > read as a 5 minute exposure would actually require ten > minutes or something like that, and the longer the metered > exposure the more compensation was necessary. With digital > if it says 10 minutes you expose for 10 minutes, and the > colors don't go funky as with color film. > > Rich > > > On Nov 20, 2008, at 10:36 PM, Emily L. Ferguson wrote: > > > Apparently there is no reciprocity failure in digital. > Apparently it's a characteristic of film, or something > like that. I did a shot quite a few years ago which > required at least 20 seconds or something like that and it > came out all blue (dawn shot) and checked in with a photo > forum I used to frequent. There was some explanation, but > I'm not a techie, so I don't remember the details. > > --Emily L. Ferguson > > mailto:elf@xxxxxxxxxxxxxxxxxx > > 508-563-6822 > > New England landscapes, wooden boats and races > > http://www.landsedgephoto.com > > http://e-and-s.instaproofs.com/ > >
