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<< Resources Index - Understanding ISO / ASA


The International Standards Organization has approved a standard
measuring system for film/sensor sensitivity to light which is ISO.

ISO values are marked as arithmetical numbers on
photographic films or in digital cameras settings as follows:

50, 100, 200, 400, 800, 1600, 3200

The bigger the ISO number, the greater is the sensitivity to light.
Each time the ISO speed is doubled, the exposure must be halved, and opposite.

For example, if the correct exposure for a given scene will be 1/250s at F8 with a ISO 100 film/setting, the same scene photographed at ISO 200 would need a half of the initial exposure, meaning 1/500s at F16,
to ensure a correct exposed image.


Equivalences between film ISO senitivities
      DIN
  (Deutsche
   Industrie
   Normen)  
  Germany		  ASA / ISO
(International Standards Organization)
      USA		      GOST
  (Gosudarst
   Venai
   Standard)
    Russia		   SCHEINER
 
 
 
    Europe
       10           8           8        20
       13         16         16        23
       15         24         22        25
       17         40         45        26
       18         50         45        28
       20         80         65        30
       21       100         90        31
       22       125       130        32
       27       400       350        37
       30       800       700        40
       33     1600     1250        43

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