Why 160?

Discussion in 'Color: Film, Paper, and Chemistry' started by AlexG, Oct 9, 2009.

  1. AlexG

    AlexG Member

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    I've been dying to know this for years.


    Why 160 ISO/ASA? Why is 160 such a good speed? Why are most "professional" portrait films 160?

    Even my light meter goes 25, 50, 100, 160, 200, 300....and so on.


    Why is 160 so special?


    Alex
     
  2. Sirius Glass

    Sirius Glass Subscriber

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    To drive you crazy! [It is half the speed of Tri-X 320!]

    Why do olives come packed in salt water and sardines come packed in olive oil? :confused:

    Steve
     
  3. jnanian

    jnanian Advertiser Advertiser

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  4. Q.G.

    Q.G. Inactive

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    160 is just a number on the scale.
    One that corresponds to a value on the old DIN scale as well (every DIN value step is 1/3 ASA step).
    ISO 160 is ISO 100 + 2/3. Your lightmeter should also have 125, ISO 100 + 1/3.
     
  5. Chris Nielsen

    Chris Nielsen Member

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    If clocks go clockwise because of the sundial and sundials run anticlockwise in the southern hemisphere, then clocks down here should run anticlockwise as well, shouldn't they?
     
  6. 2F/2F

    2F/2F Member

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    Is it because it is not as fast as 200, and not as slow as 125?
     
  7. Ektagraphic

    Ektagraphic Member

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    Maybe when they tried to develop a new emulsion something went right at ISO 160 so others followed...
     
  8. Mike1234

    Mike1234 Inactive

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    Cuz it's kewl!!
     
  9. jnanian

    jnanian Advertiser Advertiser

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    you mean they don't ?!
    i think you need to ask for a refund :smile:
     
  10. tiberiustibz

    tiberiustibz Member

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    They probably found a speed improvement that gave them the fine grain they wanted at 160 ASA. Ektar is 100 ASA though.
     
  11. Ektagraphic

    Ektagraphic Member

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    Maybe it's because it eliminates the need for a complany to offer a 100 and a 200 speed film. 160 is pretty much in the middle.
     
  12. Mike1234

    Mike1234 Inactive

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    Wouldn't 141 speed be closer to the middle of 100 and 200? :smile:
     
  13. Chris Nielsen

    Chris Nielsen Member

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    A friend had a wall clock that ran backwards. Very confusing!!
     
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  15. Mike1234

    Mike1234 Inactive

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    Why is that confusing? I can run backwards... sort of.
     
  16. tiberiustibz

    tiberiustibz Member

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    It's twice as close to 200 as it is to 100...
     
  17. Ektagraphic

    Ektagraphic Member

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    For me with a film such as Portra 160 serves the purpose of a 100 and 200 speed film. If I need faster I go faster.
     
  18. nickrapak

    nickrapak Member

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    They're rebels without a cause. Society wants their film speed to be a multiple of 25, but they say NO.
     
  19. Jeff Kubach

    Jeff Kubach Member

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    Why not 160!? More choices!:D

    Jeff
     
  20. jnanian

    jnanian Advertiser Advertiser

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    films have been asa 160 for a long time ..
    maybe it has to do with goldielocks
    ( not too fast, not slow but just right )
     
  21. MattKing

    MattKing Member

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    Before there was Portra at ISO 160, there was Vericolour III at 160 (IIRC). Before that, there was Vericolour II which was ASA 125 (IIRC).

    Just progress, I guess :smile:.

    Matt
     
  22. Curt

    Curt Subscriber

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    Why are the labels on Cranberries upside down according to how the can is opened? I have asked many people that and no grocer knows the answer.

    Maybe it goes with ASA 64. I use ASA because that film is long gone. What's the most unusual film speed listed by a manufacturer?

    I love those King Oscar ones. http://www.kingoscar.com/company

    My step grandfather was Norwegian, we fished and hunted and ate King Oscar Sardines, but I've told that story before...

    BTW: where is Ole these days?
     
  23. Jesper

    Jesper Subscriber

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    160 Asa as we think of it today may be strange for us, but it is 23DIN.
    Is 23 more or less logical than 21DIN (that is 100Asa) or 27DIN (400Asa)?
     
  24. mattmoy_2000

    mattmoy_2000 Member

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    To make film faster, the sensitivity has to increase exponentially, i.e. one step difference means doubling the sensitivity. In reverse, it decreases logarithmically. A similar thing happens with music. If you look at the neck of a guitar, the frets aren't spaced evenly, they get further apart the further from the body you go.
    100-200-400-800-1600 are the major steps, but each step has half and third steps between it and the next one. Because the scale is exponential, a third of a step isn't 0.33, and changes throughout the step. The difference between 100 and 125 is the same as between (125 and 160) and (160 and 200) and (400 and 500) and (5000 and 6400). These aren't exact figures because the actual figures are horrendous irrational numbers, but 160 is a lot easier to remember than some awful and negligibly different surd.
     
  25. Blacknoise

    Blacknoise Member

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    I've always wondered this too...

    And also, I've never (that I can recall) seen ISO 200 120 rolls. Do they exist?

    EDIT: Well explained Mattmoy, makes much more sense to me now! :smile:
     
  26. StorminMatt

    StorminMatt Member

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    It would be the exact middle between 100 and 200. But ISO speeds typically go in 1/3 stops rather than 1/2 stops. So you are more likely going to see ISO125 or ISO160 than ISO141.

    Maybe if clocks were invented in the Southern Hemisphere.