Pushing and Pulling Film

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Pushing and Pulling Film

• Controlling Contrast

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Why bother?

• Each combination of subject and lighting has its
  own contrast range.
• Bright sunlight usually produces negatives with
  more contrast.
• Overcast days usually produce negatives with
  lower contrast.
• Correcting contrast with printing filters can
  reduce tonal range of the print.
• Pushing and pulling film will produce negatives
  with medium contrast that will make printing
  easier and retain the largest possible tonal
  range.

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The effects of contrast filters
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Pushing Film
To increase contrast, underexpose and
overdevelop.
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Pulling Film
To decrease contrast, overexpose and
underdevelop.
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Expose for the shadows, develop for the
highlights.
Since we have much greater control over the
highlights during development, we want to
develop for the highlights. When shooting, we
want to control the shadow areas, so we expose
for proper detail in the shadows.
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Using the Zone System

• 1. Meter the scene and expose the film.
• 2. Measure the contrast of the scene.
• 3. Develop the film accordingly.

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Meter the Scene

• Find a dark part of your scene in which you want
  to retain texture and detail.
• This is a zone III.
• Meter this part of the scene.
• Your light meter is now telling you the proper
  exposure for a Zone V in this area.
• Underexpose this reading by two stops for proper
  Zone III exposure.
• Make the exposure.

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Measure the Contrast of the Scene

• Find a Zone III (textured and detailed shadow)
  area and take a meter reading.
• Find a Zone VII (textured and detailed highlight)
  area and take another meter reading.
• Including these two readings, count the stops
  between them.
• Five stops is N. Six is N1. Four is N-1.
• Mark your film so you know how to develop.

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Normal Contrast
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Low Contrast
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High Contrast
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Develop the Film

• For N, develop normally.
• For N1, Push the film one stop (overdevelop).
• For N-1, Pull the film one stop (underdevelop).
• Check your film manufacturers web site to find
  out how much time to add or subtract per stop.

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Practicality of the Zone

• Zone system works very well for large format
  photographers with handheld spot meters. Each
  exposure can be exposed and developed
  differently.
• Medium format users may have several film backs
  for N, N1, and N-1.
• 35mm shooters may find the full Zone system of
  limited practicality since a roll of 36 may be
  shot in several different lighting conditions.
  This is why many photographers choose 12 or 24
  exposure rolls.

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The Zone and 35mm

• The Zone works best when shooting under
  consistent lighting situations so that all
  exposures on the roll will need Push or Pull
  processing.
• Forgot to overexpose under contrasty light?
  Underdevelop anyway to bring down the highlights.
  
• Forgot to underexpose in flat light? Overdevelop
  anyway to push up the highlights.