Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,677   Posts: 1,482,053   Online: 886
      
Page 1 of 11 1234567 ... LastLast
Results 1 to 10 of 104
  1. #1
    PeterB's Avatar
    Join Date
    Apr 2005
    Location
    Sydney, Australia.
    Shooter
    Medium Format
    Posts
    592

    HP5+ over exposed by 4 stops, will my recovery plan work ?

    Hi folks,

    I was rather annoyed at myself to discover that I over exposed a 120 roll of HP5+ by a whopping 4 stops ! The good news is that I think my highlights will not be compressed at all but I wanted to run my solution past you.

    The SBR was 7 stops from Zone II to VIII inclusive which would have otherwise lead to Normal (N) development time. In short I plan on reducing the film development time to be that for N-1 which in my process will lower the gamma from 0.5 to 0.4

    Below you can see my analysis, but I am amazed that I can still keep my scene in the straight line portion of the curve by forcing a minor reduction to its CI/gamma/slope. I will just print using 1 grade harder MG filter. What am I going to lose out on here ? This seems too easy to recover from.

    ** warning that a bit more theory and maths will now follow... **

    I have analysed the HD/characteristic curve of HP5+ and it is linear out to at least a density of 2.1 log units which has basically been my saving grace here. Normally a neg exposed for N development in my process would result in a density ranging between 0.3 and 1.35 on the neg. [gamma=(1.35-0.3)/(7x0.3)=0.5]. 1.35 is nowhere near 2.1 but 4 stops over exposing would put the density right on 2.1, however if I reduce the gamma to 0.4 and calculate the range for Zone II to IX, you will see it comfortably makes it in. I am calculating from zone II up to Zone IX (i.e. an 8 stop range) as I want to include even the last nuance of detail in my highlights. So here is the formula:

    Gamma=0.4=(D_zone_IX_end - D_zone_II_start)/((4+8)x0.3)
    0.4=(D_zone_IX_end - 0.3)/((4+8)x0.3)
    D_zone_IX_end = 1.74.


    Now because D_zone_IX_end<2.1 , I should be OK. In fact because I still have a bit of wiggle room I could develop to N-0.5 which would give D_zone_IX_end = 1.92 Developing for N would put D_zone_IX_end right at a density of 2.1 and permit no room for any error in dev time/temperature/age/minor film exposure variations etc.


    regards
    Peter

  2. #2

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,257
    Exposure determines where the values fall on the characteristic curve. Development alters total and local contrast (ie the shape and slope(s) of the curve). So minus development compresses contrast. It does NOT move the exposure range down the curve.

    Therefore in a case where you don't need to reduce contrast, if you are going to reduce development, do it because you want to slightly offset any increased graininess associated with overexposure. Other than that it will not improve anything. All it can do is decrease local contrast, particularly in the highlights, which is exactly what you indicated you didn't want. In other words, all reduced development can do is reduce the slope (ie contrast) of the straight line, and also shorten it.

    N-1 is a pretty mild contraction, but I'd still say develop normally. From the perspective of sensitometry, you can't correct for overexposure with reduced development.

  3. #3
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,279
    Blog Entries
    3
    Images
    19
    I'd go normal too.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  4. #4
    PeterB's Avatar
    Join Date
    Apr 2005
    Location
    Sydney, Australia.
    Shooter
    Medium Format
    Posts
    592
    Thanks Michael and Mark.

    Michael, have a look at figure 4 here. It shows graphically what I thought happens to the curve's shoulder with increasing development times. Basically the shoulder moves up and to the left of the HD curve (Dmax of the film eventually causes the shoulder to clip as dev time is increased). Two other examples. Here showing the HD curve for TriX and another example using AZO paper (which I assume could be applied to film in general) here in chart 3 . Both show the shoulder moving up and to the left with increasing development time. If I draw a vertical line say mid way along the straight line portion off all those curves and then start moving to the right (up) each curve, one will traverse a longer stretch of the straight line portion on the traces with less development. Note that I'm not seeking to shift the exposure range down the curve, I always lock the exposure range to the horizontal axis. Less straight line portion this means less over exposure latitude.

    Finally on p. 230-232 of WBM 2e there are also some pertinent notes on Exposure Latitude. Near the end of p.231, we read "when in doubt it is better to err on the side of under-development allowing for more exposure latitude".

    regards
    Peter

  5. #5
    Bill Burk's Avatar
    Join Date
    Feb 2010
    Shooter
    4x5 Format
    Posts
    2,909
    Images
    46
    In general, you take a normal scene and develop N-1 and use a higher paper grade or filter to print.

    That's a general reciprocity idea.

    You figured that you are on the straight line. So you could develop Normal and use the same paper grade or filter as if you had exposed normally. The contrast should be the same as you would have normally gotten. You would develop less if you expected a longer than normal scale subject would have shadows still at 0.3 and highlights at 2.1, but yours isn't going to have a thin shadow.

    You will have a density 1.05 to 2.1 if you develop normally, and the only difference from a perfect normal negative that you would print for 16 seconds is that you will print this one for 40 seconds.

    I am generalizing however. You will have more grain. To reduce that, your original plan to develop N-1 is fine.

  6. #6
    PeterB's Avatar
    Join Date
    Apr 2005
    Location
    Sydney, Australia.
    Shooter
    Medium Format
    Posts
    592
    Thanks for your observations Bill. I didn't know that increased exposure results in more grain.
    A max density up to 2.1 is right on the cusp of HP5+'s shoulder and leaves me no room for deviations/error in other process variables which is why I am inclined to dev to N-0.5 or N-1.

    regards
    Peter

  7. #7
    Tom1956's Avatar
    Join Date
    May 2013
    Location
    US
    Shooter
    Large Format
    Posts
    1,684
    I am nobody qualified to interject with any sensitometric evidence. Only intuition. And I'd tend to believe a lot of picture information and local contrast has been pushed up or over the shoulder. And the only hope would be undervelopment. Trading one bad thing for another in this case is the only possible hope. The first remedy that sprang to mind was pyro, but I have no experience with the stuff to back up my thought. However, "normal" development is something I'd discount immediately and close my mind to it.

  8. #8
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,279
    Blog Entries
    3
    Images
    19
    Peter I think you are thinking too hard on this.

    If these shots are really that important just shoot another roll the same way in a similar situation, cut it in half develop both ways and see which you prefer.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #9
    PeterB's Avatar
    Join Date
    Apr 2005
    Location
    Sydney, Australia.
    Shooter
    Medium Format
    Posts
    592
    Mark, they REALLY are that important. It will take me another 2 days to travel out and back to get the shots again ! This exercise will provide all of us with valuable insights to apply next time we accidentally overexpose a roll of film by at least 3-4 stops. If my approach turns out not to work I suppose I could spend the time taking them again, but at least I want to give this roll the best opportunity for success.

  10. #10
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,279
    Blog Entries
    3
    Images
    19
    I feel for you, many of us, me included, have already made these mistakes, we know what happens with our subject matter and our techniques and our tools. For me 4 over is an oh well got a little extra grain moment, 4 under though, now that gets me grumpy.

    There are lots of variables here, the only real way to see what you're going to end up being acceptable given your subject matter, using your techniques and your tools, is to test.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

Page 1 of 11 1234567 ... LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin