help me with different ISO's :(

Discussion in 'Film Discussion and Q & A' started by letsbefriends, Sep 23, 2008.

  1. letsbefriends

    letsbefriends TPF Noob!

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    1.) I am using a hasselblad (just learned) for my studio and light class. My teacher instructed us to buy 160 speed tungsten film. The store informed me that they no longer made it.. only 64 speed. So I had to buy that...
    Now, I bought Fuji Instant film 100 speed which is also the lowest speed they had (like Polaroid) to test the exposure. How is this going to work/ how do I compensate with different speed film?...
     
  2. Kegger

    Kegger TPF Noob!

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    What store did you go to first off.
     
  3. letsbefriends

    letsbefriends TPF Noob!

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    adorama
     
  4. compur

    compur No longer a newbie, moving up!

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    Depends on what store you went to. :)lol: joke)

    Test with your ISO 100 film and then load your 64 ISO film and reduce
    exposure by 1/3 stop.
     
  5. Helen B

    Helen B TPF Noob!

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    Increase exposure by 2/3 stop, surely?

    Which Fuji instant film did you get for testing? B&W or colour? (As an aside, the person at Adorama was perfectly correct - there is no ISO 160 tungsten still film manufactured any more. There may be some still available on eBay, or still in stock at some stores.)

    The two films will have different spectral sensitivities. If you bought FP-100C (colour) you may wish to use an 80B or 80A filter when assessing exposures in tungsten light and compensate for the light loss through the filter. It is/was more common to use B&W instant film for assessing exposure in tungsten light.

    Whatever you use, I suggest that you do tests to compare the effective speed of the two films (and your light meter) in the type of lighting that you will be using (colour temperature and approximate intensity). That means metering with your meter, finding the best exposure for the instant film, calculating the effective speed of the instant film according to your meter, adjusting the exposure for the nominal speed of the reversal film then taking a series of exposures, bracketing in 1/3 stop intervals. Then you get the film developed and see which exposure you like the most. That gives you a correlation between the instant film and the reversal film, an idea of the dynamic range comparison (you need that if you are particular about the shadows and/or highlights) and experience of how the two films behave.

    Make sure that the exposure times you are using are not so long that correction for reciprocity failure will be required for either film.

    Best,
    Helen

    PS There were slower Polaroid instant films, and there was tungsten-balanced Polaroid 64T sheet film. Polaroid Type 55, a B&W sheet film, was often used for proofing for ISO 64 tungsten film, however.
     
    Last edited: Sep 24, 2008
  6. compur

    compur No longer a newbie, moving up!

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    Yes, increase, not decrease. My mistake.
     
  7. bhop

    bhop No longer a newbie, moving up!

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    Maybe let your instructor know that 160 iso doesn't exist anymore and ask him if he wants to modify the project. It seems everyone in your class is going to have the same issue.
     

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