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Question about symbols on my light meter.


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#1 VincentD.

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Posted 25 July 2006 - 05:26 PM

Hey everybody, I just bought a light meter today but there are 2 settings on it that I don't understand. They are the DIN and ASA numbers. I would like to know what those numbers are, and how to decide what setting to put them to. Thanks!
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#2 David Mullen ASC

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Posted 25 July 2006 - 06:35 PM

Read this:
http://en.wikipedia....wiki/Film_speed

Most of us here work using the ASA system (which is now the ISO rating, which is now the E.I. rating...) instead of the German DIN system for rating a film speed -- I guess DIN is similar to ND filter strengths in that every 3 degrees equals a doubling of speed (one stop more speed), just like an ND.30 filter equals cutting the light in half (one-stop loss.)

So take the E.I. ("Exposure Index") value of the stock listed on the can and input that as your ASA rating on the meter (if you choose to use the stock at its recommended rating -- people often use the next lower ASA rating in order to overexpose the stock a little. For example, rating E.I. 250 stock at E.I. 200 will overexpose it by 1/3 of a stop.)

The American Standards Association (ASA) became the International Standards Organization (ISO) but the old term has stuck. (Does ISO and ANSI overlap in their duties?) Kodak switched to the E.I. rating (which is still the same basic system) because it gives them the flexibility to assign a rating that is optimized for the look of the stock rather than a strict calculation based on density. But essentially 100 ASA, 100 ISO, E.I. 100, all mean the same thing.
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