light sensitivity
Light sensitivity is the term used for the sensors ofdigital cameras and film material. These are values standardized by the International Standards Organization( ISO) and the American Standards Association( ASA) for the detection of brightness signals. There is also the system developed by DIN (Deutsches Institut für Normung e.V.). The International Standards Organization (ISO) combines the ASA and DIN values and separates them with a slash, example: 100/24.
The ASA scale is linear; an ASA value of 200 has twice the light sensitivity of one of 100 ASA. Light sensitivity scales are based on a camera's f-stops. A doubling of the ASA value corresponds to an increase of one f-stop or twice the shutter speed.
DIN values are different. The DIN scale is divided into degrees and scaled logarithmically. 3 degrees correspond to a doubling of the light sensitivity. Thus, a light sensitivity of 21 degrees is half as sensitive as one of 24 degrees. An increase in the DIN value by 3 corresponds to one f-stop. There is a mathematical relationship between the DIN value and the ASA value.
In addition to the ASA and DIN values, there is also the Exposure Index (EI), in which the light sensitivity of professional film material is specified. It is a dimensionless number, with EI100 corresponding roughly to ISO 100 or DIN 21.
The light sensitivity values are used for films, CCD sensors, CMOS sensors and other light-sensitive sensors. However, as light sensitivity increases, so does the image noise ofimage sensors. Increasing the light sensitivity of image sensors can be achieved by combining several pixels into one larger pixel. This combination is called binning.