ISO of paper

Discussion in 'B&W: Film, Paper, Chemistry' started by Ray Heath, Mar 31, 2006.

  1. Ray Heath

    Ray Heath Member

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    what is the meaning of ISO ratings on photographic paper?

    how, or do, these ratings correlate to film ratings?

    what are ISO (R) ratings?

    what are ISO (P) ratings?

    any info greatly appreciated
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    Ray;

    The paper ISO has no meaning when compared to a film ISO. It can only be used when comparing speeds of various papers.

    I have exposed Ilford MGIV paper in-camera at an ISO of 25 and gotten a good exposure with varying contrast depending on the color of the objects. This relates in no way to the actual paper ISO though.

    PE
     
  3. honerich

    honerich Member

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    Hi Ray,

    * the ISO-P rating gives the speed of the paper: double ISO value means half of the exposure time. Unfortunately exposure meters that are calibrated in ISO-P values are hard to find. This ISO-P value has nothing to do with the ISO rating of your rolls.

    * the ISO-R rating gives the grade of the paper: ISO-R divided by 100 is equal to log(D), which defines the contrast behaviour of the paper. E.g. Ilford Multigrade IV has an ISO-R range of 130 for grade 1 and 90 for grade 3 (see details in data sheets, that come with the paper). The higher the ISO-R value, the lower the contrast of the print.
     
  4. j-fr

    j-fr Member

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    The answer to all your questions can be found in:
    The Variable Contrast printing Manual by Steve Anchell, published by Focal press in 1997.
    Guess you can find it on: amazon.com
    Probably the best book on the subject
     
  5. j-fr

    j-fr Member

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    The answers to all your questions can be found in:
    The Variable Contrast Printing Manual by Steve Anchell, published by Focal Press in 1997.
    Guess you can find it on: amazon.com
    Probably the best book on the subject.