Need explanation ^^ : "push and pull up to 1 1/2 stops"

Discussion in 'Exposure Discussion' started by Kruger, Jul 12, 2013.

  1. Kruger

    Kruger Member

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    Hello everyone,

    I hope this is the right subforum for this question. Several times in blog articles or websites etc, I saw people talking about a process that is similar to this quote: "push and pull up to 1 1/2 stops". What does it mean please ? Thanks a lot !
     
  2. michael_r

    michael_r Subscriber

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    It depends on the context but briefly/generally:

    Push: Underexposure combined with overdevelopment. This is done either for aesthetic effect or because there is not enough light to give full exposure based on the film speed. So overdevelopment is used to squeeze slightly more shadow detail/contrast out of the film.

    Pull: A little less clear depending on the situation. But generally it refers to reduced development to reduce contrast. This is often combined with increased exposure to give more full/open shadow detail (which can be lost when development is reduced).
     
  3. Kruger

    Kruger Member

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    Thank you Michael ! Push will lower the exposure of the film roll ? Can I do overdevelopment without underexposure ? I have to tell them to do it when they develop the roll or I can still do it with the negatives ?

    Also what does the "1 1/2 stops" mean please ?

    Thanks again !
     
  4. jnanian

    jnanian Advertiser Advertiser

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    hi kruger

    each stop doubles or halfs the light going into the camera hitting the film.
    changing your shutter from 60 to 30 doubles the light, changing from 60 to 125 halfs the light
    just like going from f8 to f5.6, and f8 to f11 ... manually adjusting the asa/iso value that is connected to your camera's meter
    will do the same thing ... going from asa 400 to 200 doubles the light, asa 400 to 800 halfs the light ...

    adjusting the iso or fstop gives you more control on how much you over or under expose your film, since your camera can't
    go in - between shutter speeds ...

    you will have to have the lab over or under develop the whole roll, it can't be done after the fact ...
    you can over and under develop single frames on the roll, just by how you expose it ...

    sometimes the best thing to do is to shoot a few rolls, and "bracket" your exposures so you expose 1 shot right-on what the meter says,
    one with 1 stop more light, and one with 1 stop less light so you can get an idea of what your lab ( and camera )
    is actually doing before sending them anything important ...

    depending on the film you are using, sometimes the makers don't recommend anything but processing "normally" with 1 stop over or under exposure
    because the film has 1 stop leeway built in to it ...


    john
     
  5. michael_r

    michael_r Subscriber

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    Kruger:

    When I refer to underexposure in a push scenario I mean that you are treating the film as if it had a higher speed than it does. Push simply means overdevelopment. It doesn't decrease film speed. It actually helps maximize whatever speed the film has. What I meant is that this overdevelopment technique is often used when people want to try to use their film at a higher speed because there is not enough light. So for example, someone using an ISO 400 film might expose the film as if it were an 800 speed film (which means underexposing), and overdeveloping in an attempt to compensate for lost shadow detail. Exposing a 400 speed film at 800 and overdeveloping ("pushing") would be a 1 stop push.
     
  6. wy2l

    wy2l Member

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    Push: A method where film is made to be more sensitive to light that the manufacture's rating. Under expose the film, and then leave the film in the developer longer than the manufacturer's suggested time. As a result, film speed is increased, but negative contract is increased.

    Pull: A method to decrease film contrast, by over exposing the film, and then under developing. The opposite of Pushing. Adds more details to shadow areas.
     
  7. michael_r

    michael_r Subscriber

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    The film is not made more sensitive to light by pushing. Sensitivity is a property of the film. Pushing is simply overdevelopment in attempt to bring out whatever shadow detail was recorded by the film.

    There is a difference between an emulsion's sensitivity to light and film speed. Sensitivity is a property of the emulsion. Film speed is based on the amount of exposure required to produce a specific set of densities under a standardized development procedure. Exposure index is a "personal" film speed based on subjective preferences and varying conditions.

    Some references which may help:


    ISO and Film Speed
    http://www.kodak.com/global/en/professional/support/techPubs/cis185/cis185.pdf

    Pay particular attention to point 2d regarding pushing

    Pushing Refer to page 18 "All about pushing..."
    http://www.kodak.com/global/en/professional/support/techPubs/o3/o3.pdf
     
    Last edited by a moderator: Jul 12, 2013
  8. tkamiya

    tkamiya Member

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    I'm going to say this very simply ignoring all intricacies....

    Push - treat the film as higher ISO than rated on box
    Pull - treat the film as lower ISO than rated on box

    Stop - relative unit measure of exposure. 1 stop means twice as much or half as much

    So say you have a film rated at ISO 400. If you put it in your camera and set your ISO dial to 800, you are PUSHing. Further, you are pushing by ONE stop because your aperture/shutter speed combination will provide half as much light to the film.

    Also, say you have a film rated at ISO 400. If you set your camera to ISO 200, you are PULLing. Further, you are pulling it by ONE stop because your film will get exposed twice as much.

    Because your film will be over/under exposed, most of the time, development time gets adjusted. Typically more or less 20 to 25%. This is done to get the density/darkness of the film about right.

    It gets infinitely complex from here but that's pretty much the basics.
     
  9. MattKing

    MattKing Subscriber

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    It is very rare that I'll disagree with tkamiya, but ...

    The "Pushing" part really refers to the development part of the process. As does the "Pulling" part.

    If you want to increase the contrast of your negatives, you Push development.

    If you want to decrease the contrast of your negatives, you Pull development.

    When are you most frequently likely to want to increase the contrast of your negatives? When the light is so low you are forced to give the film less light than normal - i.e. under-expose it.

    Most people accomplish that under-exposure by using their meter set at one, two or more stops higher. Than they choose the Push development that corresponds to the amount of stops they under-exposed the film.

    A Push development doesn't really increase the density of the parts of the negative that correspond to the darkest parts of the scene. What it does is increase the contrast of those parts of the negatives that are in the mid-tones or shadows that are close to the mid-tones. So they print better. At the same time, a Push development increases the contrast of the highlights, which can make them harder to print.
     
  10. tkamiya

    tkamiya Member

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    Matt,

    I'm well aware of that. Knowing OP is at very beginning stage, I'm sticking with textbook explanation of pushing/pulling. I'd rather have op get the ballpark explanation than getting buried in technical accuracy and lose the big picture.
     
  11. MattKing

    MattKing Subscriber

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    I know you know.

    I just think that it is really important for beginners to understand that pushing and pulling are development controls, that influence exposure, rather than exposure controls, that influence development.
     
  12. michael_r

    michael_r Subscriber

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    This is why I suggest OP read the "all about pushing" section of the Kodak document I posted.