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Thread: ASA n/a ???

  1. #1
    thefizz's Avatar
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    ASA n/a ???

    I have been looking at the massive development chart on digitaltruth.com and see some film speeds as n/a (not applicable).

    Can someone explain how a film speed can not be important when choosing which development time to use.

    Regards,
    Peter

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    clogz's Avatar
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    It simply means that at a certain film speed the developer will not give good results. Also, I might be that no data on the combination is available.

    Regards

    Hans
    Digital is best taken with a grain of silver.

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    thefizz's Avatar
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    How is one to know which film speed will work or not?
    The chart still gave developing times?

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    Peter,

    Test for yourself and contribute the data if you get acceptable results. It helps to know the properties of the film and developer you want to use.

    I was really surprised not to find times for HP5+ @200 in Rodinal 1+50 on the list before. I tried and tested and sent in the result for 135 and 120 format.

    G

  5. #5
    thefizz's Avatar
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    Thanks for your views Geert & Hans. I still don't understand why they show a dev time & temperature without any film speed but I agree about testing as some of the info on digitaltruth is a little off.

    I hope that's a Leffe beer your having in you profile picture Geert.

  6. #6

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    If there is no speed listed, then I'd assume the times are for the film's "box" speed.

  7. #7

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    The Massive Dev Chart is made up, in part, of user-supplied times. Thus, my guess is that somebody submitted a development time but neglected to mention the film speed.

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    BTW, don't forget that development also depends on the method of agitation: by hand (multiple varieties) or in a rotary drum.
    In the best case, the times at Digitaltruth are only a starting point for your personal dev. combo.

    Quote Originally Posted by thefizz
    I hope that's a Leffe beer your having in you profile picture Geert.
    It's shaken Rodinal disguised as Leffe

    G
    Last edited by argus; 06-24-2005 at 02:24 AM. Click to view previous post history.

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    Paul Sorensen's Avatar
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    I just had a look at the dev chart and the films I saw with the NA were infrared and ortho films. Here is a quote from Kodak's web site about their infrared film:

    Film speed: Normal ISO speed values do not apply. Make trial exposures under typical conditions. With a KODAK WRATTEN Filter No. 25, try a setting of EI 50 (daylight) or EI 125 (tungsten) and bracketed ± 2 stops
    I imagine that because of the limited sensitivity of ortho films, that they present a similar problem for metering, but I am not really sure about that. Otherwise, I didn't find any other instances of the NA being listed for the film speed. There were a few where the film speed was listed as ? and I can only assume that was a case where the info that they received was incomplete but they still deemed it useful.

    I hope this helps,

    Paul.

  10. #10
    thefizz's Avatar
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    Thanks Paul, yes it was IR film I was checking but as some times included film speed I thought it strange for some not to. I still think it's pointless providing dev times without film speeds. I have since done a little trial & error and have nailed down a good combination for Maco 820 Aura.

    I ended up with dev time of 10 & half minutes in rodinal 1:14 exposing the film at 100ASA and making the necessary exposure adjustments for filters. Next I want to try Rodinal at a more dilute mix.

    Peter

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