We've all talked about the triangle of photography: Shutter Speed, Aperture, and ISO. But have you ever stopped to think what ISO really stands for?
ISO is the culmination of three different systems for measuring camera sensitivity, including the The American Standards Association (ASA) and the Deutsches Institut für Normung (DIN) standards. Both of these were in use until as recently as the mid-1979, when the International Organization for Standardization (ISO) stuck an oar in and added their own initial set of definitions.
Today's ISO values are defined by ISO 12232:2006 (that is, ISO standard number 12232, revised in 2006). This ISO standard "specifies the method for assigning and reporting ISO speed ratings, ISO speed latitude ratings, standard output sensitivity values, and recommended exposure index values, for digital still cameras. ISO 12232:2006 is applicable to both monochrome and colour digital still cameras."
So now you know. For the ultimate piece of photographic trivia, memorise "ISO 12232", and the next time your unworthy photography friends start harping on on about 'ISO', you can pull your smug face and go "Well, actually, did you know..."
For extra geek cred, dig out your credit card and shell out the 92 Swiss Francs (USD 110 / GBP 67 / EUR 75) it costs to buy the full ISO standard and read the whole thing.
Oh geeky, delicious, photography nerd love-fest. How we love thee.