Can you really push film ?

Discussion in 'B&W: Film, Paper, Chemistry' started by Peter Rockstroh, Jun 21, 2005.

  1. Peter Rockstroh

    Peter Rockstroh Member

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    For the past weeks I´ve been reading posts that discuss different film, exposure index and developing combinations, giving single films different speeds, according to these combinations. I understand that any given film has a given light sensitivity, depending on silver grain size, shape and distribution. That would imply that each film has a single threshold that defines its "speed."
    Wouldn´t this mean that any attempt to push the film - meaning to move the light sensitivity threshold further down - is only going to produce underexposed and overdeveloped images ?
    The only thing it seems to achieve is pushing the mid-range of tones further up the straight portion of the curve, but you are not really making film faster, in terms of requiring less light for the same tonal scale.
    Are there really developers that can produce a visible image from a latent image that received too little energy to react with the normal developing agents ?
     
  2. noseoil

    noseoil Member

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    Peter, the short version is that different films are affected by different developers. A good example is Efke 100. With Pyrocat and "normal" development there is one speed, but with minimal agitation, there is a boost in speed. We're not talking light years, but shadow densities are significantly enhanced by minimal agitation.

    There are different developers which affect the rate of development and film speeds.

    Your general statement about more contrast with push processing is basically true. You won't win the Kentucky Derby with a plow horse, unless all the other horses drop dead during the race. tim
     
  3. Ole

    Ole Moderator Staff Member Moderator

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    - and to pick up that metaphor, the art of pushing is to make sure any other horse would drop dead.

    Very dilute developers, very little or no agitation, very long development times is one possible route. There are very big differences between developers in how much shadow detail they can salvage, something like FX-2 is great (without the inhibitor). You sacrifice fine grain, good tonality and low base+fog density in order to get anything printable at all.

    The "advanced" way is through various forms of hypersensitation, several methods are said to work.
     
  4. Donald Qualls

    Donald Qualls Member

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    But then, if you're loaded with Tri-X and you find youreself shooting in a club or bar where flash would be a serious faux pas, isn't that a case where the other horses have, in fact, dropped dead, come up with stones in their hooves, thrown their riders, or otherwise scratched, leaving you to try to get something out of your plow horse?

    I can shoot Tri-X at EI 800 without it being obvious I've done anything to it, just by using dilution, extended development, and reduced agitation. At EI 1600, it looks a little harsh, but I usually use Diafine and don't see a lot of degradation (though I'll admit I'm not the kind of fanatic about shadow detail some Zonies are). Beyond that, it gets dicey, but I've seen images shot on Tri-X at EI 3200 that were developed with two or three passes through Diafine (with a thorough rinse after each Bath B to avoid contaminating Bath A), and heard of EI 6400 and beyond with other exotic methods.

    If midtones will get the job done (and they usually will with the kind of subject matter where you can't just tripod the camera, open the shutter, and got get a cup of coffee while you wait for enough photons to arrive), you can push a long, long way. If you want results like Ansel Adams, you'll probably wind up convincing youself that Tri-X is actually a 200-250 speed film.
     
  5. Claire Senft

    Claire Senft Member

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    With much extended development perhaps an additional stop can be reached at a large increase in contrast after that you start losing shadow detail. However, even with the loss of shadow detail, given the right elements in the photo an excellent photo can result...probably wont but can.
     
  6. Neal

    Neal Subscriber

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    Dear Peter,

    Download the latest Tri-X data sheet and look at one of the sets of characteristic curves. Clearly you can develop to increase the sensitivity to light levels, but only at the cost of increased contrast in the negative. If the scene can be compressed into the stops available you can get a nice print.

    Neal Wydra

    Neal Wydra
     
  7. mikewhi

    mikewhi Member

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    The term 'pushing' has no real meaning to people that understand sensitometry. The term hs primarily been used by photographers who did not know or care about the 'science' of photography. All they knew was that if they needed a faster ASA because they were shooting at night or whatever and they didn't have that film available, they could use their 'regular' film, rate it 1,2 or 3 stops faster, then develop the heck out of it and voila they had something in the negative and they could work it out in the darkroom. It's really that simple. I've never heard anyone who knew sensitometry even use the term 'push' or 'pull' - they know too much to use those terms.

    -Mike
     
  8. djklmnop

    djklmnop Member

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    Mike says it best. Using the terminology only shows how little one knows of sensitometry and the net effect.
     
  9. TPPhotog

    TPPhotog Member

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    Sometimes this place sounds more and more like P.Net, if I had read this thread a few years back I would have missed 1/2 of the pictures I have captured.

    Peter film is cheap and pushing / pulling (yep I use the phrase and don't give a .....) is a matter of taste. Take out a couple of rolls and shoot everything and anything, then soup them and see what you think of the results yourself :wink:

    Pushing will increase contrast and pulling will decrease contrast, but as I say it's a matter of taste.
     
  10. gainer

    gainer Subscriber

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    Whether you use the term or not, sensitometry will show that for most developers, there is an increase in shadow contrast and a decrease in the amount of exposure at the minimum usable exposure. Whether you can live with what this increase in shadow detail does to the highlights is another question. If the scene has a low brightness range, you may find overdevelopment to be exactly what you need in order to get easily printable negatives. You might call it "pushing" or you might call it making use of what you know about sensitometry. What's in a name?
     
  11. Peter Rockstroh

    Peter Rockstroh Member

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    Thanks for all the feedback. I have learned the following:
    1.- The light sensitivity threshold of any given film can be tweaked but not really pushed
    2.- If making a photo under difficult light conditions is more important than the scriptures of Saint Ansel, film can be pushed
    3.- Don´t go to the racetrack without a gun

    Thanks again,
    Peter
     
  12. Paul Howell

    Paul Howell Member

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    Pushing is term that was used by news photographers and photojounislists to let the darkroom techs know how to develop the film. I would shoot TX at 800, put the film and my record (who, what where on which frames and the exposure,) in an envelope which was sent to a lab for processing. I do understand the "science of sensitomerty" and use of the term pushing is just short hand. The trade off of loss of shadow detail and blocking highlights was made to get prints in dismal conditions when the use of flash was impractical. With the evolution from B&W to color in the 1980s most news photographers started (returned as it was standard practice in the 30s, 40, and 50s) to use flash rather than pushing color film, and I guess that the same approach is still being used for the new digitial systems. I still push film (underexposed overdevelop or use a divided developer) to shoot indoors or shoot with a long lens in dim light outdoors without a tripod. Because I still use the term push doesn't make me the village idiot.
     
  13. noseoil

    noseoil Member

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    Paul, hardly the "village idiot" by any stretch of the imagination. I've been using BTZS numbers lately and I don't even know what n, n+1 or n-1 is any more. Since I've been using SBR numbers, the rest is meaningless. Thank goodness I don't know anything about sensitometry other than it must work.

    With Efke 100, I've been a-pushin' and a-pullin' to beat the band. A rose by any other name....(sorry Eric). tim
     
  14. Donald Qualls

    Donald Qualls Member

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    If you do it correctly, you can take advantage of the "up to one stop" increase in real speed without the huge increase in contrast that usually accompanies extending development without changing other parameters.

    What other parameters to change? Dilution -- using a weaker working solution will promote local exhaustion, resulting in shadows getting more development than highlights. Agitation -- less agitation tends to promote the location exhaustion that dilution makes possible. So, dilute your developer (and use more liquid if necessary to be sure there's enough to develop the film), agitate less, and develop a lot longer, and you'll get up to about one stop increase in speed.

    I do it routinely with HC-110 on Tri-X, TMY, Fomapan 100, J&C Pro 100, and now even with a Caffenol derivative on Agfa Copex Rapid. No, I'm not claiming I get EI 800 with the shadows of 400 -- more like I get EI 400 with the shadows people derate to 250 or 200 to get, though I can do the 800 version just as readily if needed...