Push Developing HP5 & Pre-Exposure

Discussion in 'Black and White' started by andrew_o'neill|1, Jul 3, 2022.

  1. Pre-exposure is a technique I sometimes use... but I've never bothered to see its effectiveness with film that is going to be "pushed". Here is a video I put together exploring the two combined...

     
  2. In the olden days there were lots of ways to "speed up" film, including push developing, water development (stand development), pre-exposure, latensification (exposure to weak light after exposure but before development), and fuming the film with mercury vapors. The last two methods work but the results are difficult to predict and repeat.
     
  3. Pre-exposure is a easily controllable way to boost the shadows...There is a sweet spot. Going beyond that will seriously harm shadow contrast. The point of this exercise was to see if pre-exposure could help retain detail otherwise lost from just a straight push.
     
  4. It's always called "pre-flashing", but theoretically there's no reason why a post-flash exposure wouldn't give identical results.

    But, but... Why would you "push" process (i.e. over develop) a film that you're trying to restrict the contrast of? Over-developing increases contrast, thereby pushing the highlight density further away from the shadow density. Seems counter productive to do that and pre-flash at the same time. Those subjects ain't going anywhere; so why not just increase the exposure and cut the development time?

    FWIW, you can also do a flashing exposure with any digital camera that allows for multiple exposures. It raises shadow detail in the same way.
     
    Last edited: Jul 7, 2022
  5. This was just a test to see what happens. Pre-flashing film has always been known as pre-exposure. Flashing is a darkroom term. Like I said above, the test was to see if detail could be restored with pre-exposure. Naturally, I would give more exposure, then cut back on development... easily done with sheet film. Harder when you use roll film with lots of other SLR's on it. My results show that pre-exposure and push can work.
     
  6. Yikes! Don't try at home.
     
  7. I use Ilford XP2 Super 400 (C41) and never have to worry about exposure, pushing and such like-
    and all on the same roll of film....
     
  8. That's a really nice film. Sharp. But... I usually only use films who's emulsions include large format... :)
     
  9. Surely that's what interchangeable backs are for?
    You can have separate backs for N, N-1, N+1 development, etc.

    A bit of a hassle, but nobody shoots film for the convenience these days. That's for sure.

    Besides, push processing changes the true (threshold) film speed not one jot. It only increases contrast.

    Question: When you say a Zone 4 or 5 pre-exposure, is that based on the true, box film speed, or the 'pushed' EI? Because at 1600 EI with HP5, that would actually be a Zone 2 or 3 pre-flash.

    Still quite high IMO. Anything that gets more than 0.001 lux-seconds (approx Zone1) of exposure onto a 400 ISO film should theoretically overcome the exposure threshold and lift shadow detail above the toe of the H&d curve.
     
    Jochen likes this.
  10. Fine and dandy if one is shooting with a camera that facilitates separate backs. Not too many 35mm cameras out there do. The EI for pre-X was 1600 and 3200, respectively. If I had used my normal EI of 250, the pre-X density would have been excessive.
     
  11. I bet you could count the number of 35mm users that push-process and also care a jot about shadow detail on the fingers of one hand!
     
    Dave Luttmann likes this.
  12. Probably right! :)
     

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