Dave (@chang-sang.com) wrote: > How the H-E-double hockey sticks do you meter that ? My Sekonic > L308-B can only go to 8000. Every other hand meter I've seen only goes > so high so how do you compensate for ISO above 8000 ? (i.e. 12,500 > and higher)
Easy! To get the "correct" exposure for ASA 25,000, meter at 8000, then expose at 1 2/3 stops slower. Alternatively, meter at about 6,000 and expose two stops slower. Every doubling of film speed allows you one stop less exposure to capture an equivalent amount of light (neglecting reciprocity failures) -- it's a geometric progression. If thinking in terms of Base-2 logs and exponents helps (and maybe it doesn't), just think of what power you need to raise 2 to in order to get the ratio of the ASA values. In your case, if 2^n = 25,000/8,000, then n=1.64. If 2^n = 25,000/6,000, then n is about equal to 2. Saint Ansel has a log table in the back of "The Negative". Hope this helps. Bill Peifer Rochester, NY - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
