high silver film, truer to rating?

Discussion in 'B&W: Film, Paper, Chemistry' started by e_joyner, Sep 29, 2004.

  1. e_joyner

    e_joyner Member

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    Anybody have thoughts to whether higher silver content films are truer to their ISO rating? I love APX, but ran into problems when they changed emulsions. Too much contrast! I altered agitation, but it was still too contrasty.

    I've been trying to hone my developing skills, then I stumbled onto Barry Thornton's website. I did my first ISO/developing test on Delta 100 120 film. I'm not done yet, but the experiment is very interesting. I haven't had time to start testing on APX (35mm) yet. I did take a wild guess and developed my last roll for 20% less time-(from Digitaltruth the time for D-76 1:1 is 13.5 min)-so I developed for 11 min. I am much happier with the results. I've been pouring over their data sheets, and they say their film is accurate to +/-1/6 stop(I think that's right). When you read the developing recommendations, it shows a slightly higher effective ISO rating using the time/soup guide.

    I *do* plan on doing testing following Barry's outline, but was wondering if any of you have tested APX and what were your observations. I know it's 'subjective', I'm just curious.

    Sorry about the seemingly endless questions in this post.

    edye
     
  2. gma

    gma Member

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    I am curious to read about what others have observed, but I think some manufacturers' speed ratings are exagerated strictly for marketing purposes. I always expose at lower EI's than published.
     
  3. rjr

    rjr Member

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    IMHO that´s true, with two exemptions.

    - 100ASA color negative films of all brands usually have an actual rating of around 160ASA

    and

    - the Adox/Efke type emulsions are faster than the package print and don´t like being overexposed.

    With bw it heavily depends on what developer you choose to use. APX100 (in Rodinal) and Scala (in Scala reversal process) pretty much fulfill their promises.
     
  4. chrisg

    chrisg Member

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    With normal (seven stop) scenes I've found HP5 is fine at 400 when developed in D76. I rate it at 200 or 250 for reduced development time with nine stop scenes. I get an extra stop out of it when I develop with DDX.

    I rate FP4 at 100 with D76. DDX seems to give it an extra stop as well.

    As indicated in the previous, the developer can make big difference.