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  1. #1

    Join Date
    Jun 2007
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    Austin, TX
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    Film ISO rating temperature

    Can anyone explain what the temperature measurement frequently paired with an ISO rating means? For instance, I have a box of HP-5+ here that says it's "ISO 400/27 degrees". Some Fuji Pro 160S says ISO 160/23 degrees.

    Should I be altering my film speed for ambient temperature?

    Temperature is on my mind since getting a Jobo - I have to use ice baths to get the water bath (filled with cold tap water) down to 75F for b+w developing.

  2. #2

    Join Date
    Nov 2004
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    No. It's the older DIN system. Just ignore it. Unless you've got a meter that lets you set to European DIN instead of ASA. I think ISO is supposed to be a bit of a cross between ASA and DIN so they show both numbers.

  3. #3

    Join Date
    Jun 2006
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    Sweden
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    It is the sensitivity of the film in the older DIN*-scale values.

    33 DIN = 1600 ASA = 1600/33 ISO
    30 DIN = 800 ASA = 800/30 ISO
    27 DIN = 400 ASA = 400/27 ISO
    24 DIN = 200 ASA = 200/24 ISO
    21 DIN = 100 ASA 100/21 ISO
    18 DIN = 50 ASA 50/18 ISO
    15 DIN = 25 ASA 25/15 ISO

    *Deutsche industrie norm = German industry standard
    /Markus

  4. #4

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    Thank you! I hadn't noticed that they were all the same for a given ISO.

  5. #5

    Join Date
    May 2006
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    It's not older: it's still current, though less popular. 3 degrees = doubling, because it's logarithmic.

    Most people find arithmetic (the first number) easier. Once you're used to DIN, there's nothing in it.
    Free Photography Information on My Website
    http://www.rogerandfrances.com



 

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