A term that gives an indication of the speed, or sensitivity to light, of photographic film. The higher the number, the faster, or more sensitive, a film is. With slide film, if you set the exposure index (E.I.) too high, the film will look darker (underexposed.) Setting it too low will result in overexposed pictures that look too light. Experiment with slight adjustments to the manufacturer's recommended E.I. to achieve the look you desire.
When film is shot at something other than its rated speed setting, or ASA, that speed setting is referred to as the Exposure Index. For example if Kodak Tmax 100 is exposed at 50, the exposure index for that film would be referred to as EI 50. See also: ASA
Number which is used to measure a film's speed based upon the film stock's sensitivity to light. Similar to A.S.A. and I.S.O.
AKA "E.I." or "ASA." It is the specific number used to measure film speed.
Film Speed designates how sensitive a film is specified to be. EI or Exposure Index specifies the speed at which you are rating the film. In the film speed example, my comment suggests exposing Kodak Royal Gold 1000 at an EI of 800. Note that using an EI different from the film speed will have side effects ... By using an EI different from the recommended value there is something to take into consideration when development occurs. If normal development is used you will essentially be performing push or pull processing on the film you exposed! On the other hand, if you adjust the development process to match the EI you exposed the film at, then everything is as expected. This is a more significant issue with color (C-41) process films than B&W, as temperatures and times for C-41 are strict, compared to the changes you can make to B&W processing. Of course, if you send the B&W off to a lab for standard processing, you will be affected the same way. After writing this I realize my grasp of the cumulative effects is not complete and that I need to study this further.
A number that indicates a film's effective speed.
Exposure index, or EI, in photography refers to film speed rating assigned to a particular film by a photographer in order to compensate for equipment calibration inaccuracies, process variables, or to achieve certain effects. Exposure index may or may not be the same as manufacturer's film speed rating for that particular film.
