ISO

I.S.O

           

I.S.O is the indication of how sensitive a film is to light. The lower the ISO number (100, 200, 400, 800), the lower the sensitivity of the film and the finer the grain in the shot, whereas a higher ISO gives more noise or grain. Higher ISO settings are used in darker shots/locations to give a faster shutter speed.

High ISO


cut1 from Simmone Dudley on Vimeo.

Low ISO


Low ISO from Simmone Dudley on Vimeo.

Because one-third stop is the minimum exposure difference detectable by the unaided eye, film sensitivity is rated in no finer increments than this. This makes the relationship between intervals easier to see. For example ISO 200 is 1 stop faster than ISO 100, and ISO 320 is 1 stop faster than ISO 160. It makes it easier for odd intervals as well, like ISO 80 and ISO 32 (1^1/3 stops).