Need help with underexposed 4x5 Arista, reciprocity

Discussion in 'B&W: Film, Paper, Chemistry' started by horacekenneth, Mar 16, 2013.

  1. horacekenneth

    horacekenneth Member

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    I was shooting Arista 100 EDU @ 75asa using a little Sekonic incident light meter. Most of my exposure times were at 2 seconds between f8 and f11, it was an overcast afternoon/evening.
    Right before my last shot I checked the Pinhole Assist app on my iphone, based on their curve for Arista 100 EDU it said that if my light meter thought 2 seconds was right I should've given it ~9 seconds. BUT if the light had been one stop brighter, two seconds would have been perfect.

    So...does that mean I can develop everything N+1 and call it good? A one stop push? That seems too easy.
     
  2. MattKing

    MattKing Subscriber

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    A push development doesn't increase detail - it just increases contrast for the detail that made its way on to the film.

    So the push may help it look a bit nicer, but it won't solve your problem with very low light levels leading to reciprocity failure.
     
  3. horacekenneth

    horacekenneth Member

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    That makes sense, thanks. Does a one-stop push sound about right for recovering what I can?
     
  4. Maris

    Maris Member

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    My experience with Arista EDU ultra 100 is that the reciprocity failure is nowhere near as dreadful as the official figures imply. For a 2 second exposure I would not make any correction at all. Here are the numbers I use:
    1 second metered give 1 second.
    4 seconds metered give 5 seconds.
    15 seconds metered give 20 seconds.
    30 seconds metered give 45 seconds.
    2 minutes metered give 4 minutes.

    The problem with compensating reciprocity failure is that the highlights don't fail but the shadows do. The longer the exposure the further apart the highlights and shadows get. This means a severe increase in contrast . A partial solution is to give an enormously extended exposure so the shadows register and then do a very contracted development so the highlights don't block. The experiments necessary to define all of this are tedious to say the least.
     
  5. pinholic

    pinholic Member

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    Hi, Thank you for this information. The chart in Pinhole Assist are based on Arista official data which is scarse : (1 second -> 2x, 10 seconds -> 8x, 100 seconds ->16x).
    The charts within PinholeAssist for Arista were made with this data, using linear interpolation. I should have used interpolation on the derivative
    For t=2s, the 1st method gives 10 seconds, and the 2nd method 5 second.
    For t=4s, the 1st method gives 28 seconds, and the 2nd method 16 second.

    This is better, but still higher than your figures.
    I will release an updated (with 2nd method) data file soon. I would like to distribute an alternate correction curve based on your data, if you authorize me to do so.
     
  6. mrred

    mrred Subscriber

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  7. horacekenneth

    horacekenneth Member

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    That would be great! Love your app.
     
  8. Maris

    Maris Member

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    You can use my numbers but they might not suit every one. In recent years I have changed my approach to reciprocity failure and sometimes I don't correct for it at all. Why?

    A light scene and a dark scene look different. The dark scene shows some details in the highlights but the shadows and lower tones very quickly slide down to black. What I then see is reminiscent of what film will show if reciprocity failure is not corrected. To correct or not to correct (partially or totally) is an aesthetic decision based on whether a dark scene should be represented by a dark photograph.

    If I am faced with a light scene but my optical system (pinhole, small aperture, heavy filter) mandates a long exposure then I will apply a stronger correction and use reduced development and low contrast photographic paper to bridge the brightness/darkness gap.