Nowadays when we refer to the index of the photographic sensitivity of a film, photosensitive surface or a sensor we are talking about ISO. Not everyone will know that ISO stands for International Standard Office, but even less, especially those who have been in photography for a short time and if they have only shot digitally will know that ISO is something new.

In the past, ISO sensitivity values ​​were known as DIN (Deutsche Industrie Normen), and later it was renamed ASA (American Standard Association). The ASA and ISO values ​​are identical, it only changed the name, but when handling in DIN things were different, because when the sensitivity is doubled the DIN value increases by three units, while in the ASA and ISO values ​​it is multiplied by two.

Below you have the equivalences between ISO-ASA and DIN





and so on

As a curiosity to say that in the Soviet bloc a different scale of sensitivities was used, called GOST (Gosudarstvenny Standart which means state standard) which remained until 1987. The ISO-ASA / GOST scale is this:





and so on

I hope you found this brief review that we have given to one of the most important pillars of photography curious.

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  1.   King David of the Mañanitas said

    great the contribution is direct to the personal collection! The information is not useful for the development of a photograph, but I really believe that it is a fact that not everyone knows and you can be one step ahead of fellow photographers! thanks!!

  2.   Juan Carlos said

    Thank you very much, my visit was motivated to confirm the equivalences between ASA and ISO. It has made it perfectly clear to me.

    A little clarification:

    DIN (Deutsche Industrie Normen) is a German institution for industrial standardization
    ASA (American Standard Association) is an American institution also for standardization.

    And in view of the diversity of standards, the ISO stands for International Standard Office, which does not replace any of the above. In the case of photographic sensitivity, ISO, possibly due to the greater implementation, establishes the standard taking the ASA, however, in the case of the size of the paper sheets, ISO takes the standard of the DIN.