I was listening to one of the many photography podcasts recently and heard someone mention this estimating technique.
He said he likes to make his night exposures at ISO 100 to minimize noise, but zeroing in on the exposure time at that low ISO can take a long time. So, he makes his initial exposures at ISO 6400. It turns out that the exposures length in seconds at 6400 is pretty close to the length in minutes at ISO 100. For example, a 10 second exposure at ISO 6400 would work out to a 10 minute exposure at ISO 100. Making the initial estimated exposure time at 6400 reduces the number of test exposures he needs to make at ISO 100. I had to make a little spreadsheet to convince myself. It's not exact, but the error is relatively small. Probably less than is necessary to give you a good starting point at the lower ISO. I don't do a lot of night or long exposure stuff and maybe this is common knowledge to those that do. I've been around a long time and heard a lot of "rules," but this one was new to me. gs George Sinos -------------------- [email protected] www.georgesphotos.net plus.georgesinos.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
