29 jun 2007 kl. 21.49 skrev ADavidhazy:
Hi, Anyone know of an easy way to go from EV measured at a given ASA to foot-candles falling on a scene? I tried doing it but am not sure I succeeded so before I go further I thought I'd check here for possible history on this matter. There were several (many) URLs on the web with info but sometimes they were conflicting or widely divergent in nature. Andy
Andy, unless I misunderstand you, it sounds as if you´re looking for Ansel Adams´ famous "Exposure Formula". Here it is, directly from his book "The Negative": First compute the f/stop value corresponding to the square root of the film speed in ASA (e.g., for ASA 125, you get f/11).
Then, the luminance (in candles per square foot) of a surface read by a correctly calibrated exposure meter is just the reciprocal of the shutter speed for the above f/stop and film speed.
I haven´t tried it in practice, but these are the words direct from the holy scriptures of St. Ansel himself, so they must be true...
Good luck! Per Per Öfverbeck http://ofverbeck.se "In a world without walls or fences, who needs Windows or Gates?"
