Photography terms: ISO Value
September 26th, 2007 Posted in Photography Terms, All | 1 Comment »ISO value was firstly used in film cameras. It defined the sensitivity of a film in different units such as ASA, DIN and other. For example there were different ISO values such as 25 ASA, 50 ASA, 100, 200, 400, 800, 1600, 3200 ASA and other, so that was the sensitivity of a film where the lower number meant lower sensitivity. Now when buying films, you can usually find them with 100 or 200 ASA, which is written on a film so you can see it. If you have some films beside you, check for yourself! Films sensitivity is being different by the different size of dots from which the film is being formed, in other words, different sizes of dots or cells that accept light and form a picture. Smaller means smaller dots and less sensitivity, so the bigger number means bigger dots. By the way, films with bigger light sensitivity need less light to form a picture and inversely. So it is logical to always use the more sensitive film, but there is one problem - when you take a photo off the film and put it on a paper, the dots could be seen and they are not so pleasant to be seen. So the most common ISO values, as I said are between 100 and 400 ASA. Read the rest of this entry »
