Jump to content


Photo

Pushing and Pulling Film


  • Please log in to reply
6 replies to this topic

#1 Jase Ryan

Jase Ryan
  • Basic Members
  • PipPipPip
  • 119 posts
  • Cinematographer

Posted 25 March 2009 - 04:15 PM

I'm not clear on all reasons to push or pull film and exactly what happens to the image. Can someone please explain more?

Push: Runs the film through the bath faster, therefore not developing it as much, giving it more of an under exposed look from what you set your exposure to on set.

Pull: Runs the film through the bath slower, developing the film more giving it more exposer to the image from what you originally set it for on set.

So, if you can't get enough light on set, you can pull the film.?

And do you get more detail on the image this way?

Please clarify in detail for dummies if you can.

Thanks.

Jase
  • 0

#2 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19765 posts
  • Cinematographer
  • Los Angeles

Posted 25 March 2009 - 04:51 PM

I'm not clear on all reasons to push or pull film and exactly what happens to the image. Can someone please explain more?

Push: Runs the film through the bath faster, therefore not developing it as much, giving it more of an under exposed look from what you set your exposure to on set.

Pull: Runs the film through the bath slower, developing the film more giving it more exposer to the image from what you originally set it for on set.

So, if you can't get enough light on set, you can pull the film.?

And do you get more detail on the image this way?


You have it backwards -- pushing is extended development, whether through time or temperature (usually longer time in the developer) and pulling is the opposite.

As you expose a negative, you make more and more silver halide grains "developable", and the more of them that get developed into silver (or in the case of color film, silver and dye clouds, the silver removed in the bleach step and beyond, leaving only color dye clouds) the more the piece of film is considered "dense".

So an overexposed scene developed normally would produce a rather dense or dark negative (since the most silver forms where the brightest areas are in the frame). And an underexposed negative would be rather thin or clear (darkest areas in the frame are represented by the clearest areas of the negative.)

Since push processing increases density, it can be used to compensate for a lack of density that would have happened from underexposure. So you could, for example, underexpose by one stop and then push-process by one stop and restore the missing density had you developed normally.

However, you can only increase the density of information that was recorded by the film, and that's based on its inherent sensitivity -- you can't increase its sensitivity by push-processing. But you can take weak amounts of underexposed information and make them more visible, but at the risk of increased graininess and contrast. You can't really increase detail over what was originally captured.
  • 0

#3 Michael B McGee

Michael B McGee
  • Basic Members
  • PipPip
  • 73 posts
  • Cinematographer
  • Santa Monica, CA

Posted 30 March 2009 - 08:34 PM

thanks David. your contributions to this site are immeasurable to all of us novice but avid DPs. thanks for your time.
  • 0

#4 K Borowski

K Borowski
  • Basic Members
  • PipPipPipPip
  • 3905 posts
  • Camera Operator
  • I.A.T.S.E. Local # 600 Eastern Region

Posted 31 March 2009 - 08:20 AM

I am starting to think that pushing and pulling film, and the increase in cost it entails, isn't worth doing for some student productions.

Basically, you're adding little if any information, just increasing contrast, nad maybe highlight speed slightly. Shadow speed remains more or less the same, so you're basically just making the highlights darker.

Assuming you are printing optically, there's a benefit to this, but if your footage is getting scanned/telecined, basically the same increase in contrast can be acccomplished for free.

Really the only problem with this approach, is that noise (dust or scratching) tends to be accentuated too, and you might see some scanner noise as well. But it si free and easy to do this sort of digital correction.


I've noticed too, that students tend to get way too inot pushing and pulling film, and get all confused about over-rating and developing normally.

Just remember that you want to err on the side of overexposure, with normal development. With good lighting, unless you're going for a grainy look, there's little if anything to be gained by pushing. Pulling is seldom done except for effect or if there are situations where you don't have enough ND filters to make a fast stock slow and it is an emergency too get the shot.
  • 0

#5 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 31 March 2009 - 10:21 AM

I am starting to think that pushing and pulling film, and the increase in cost it entails, isn't worth doing for some student productions.


Indeed, the way to learn about this is to do it yourself. B&W stills in a darkroom will teach you plenty, and for very little money compared with having a lab push or pull motion picture film.




-- J.S.
  • 0

#6 Dirk DeJonghe

Dirk DeJonghe
  • Basic Members
  • PipPipPipPip
  • 605 posts
  • Industry Rep
  • Kortrijk,Belgium

Posted 31 March 2009 - 01:52 PM

If you read Ansel Adams' 'The Negative' carefully, you will find it all in there, written decades ago and still valid. Of course with motion picture film you don't push/pull the negative to fit the scene contrast, but you work with a fixed contrast and control lighting or try to fit the interesting part of the scene.
  • 0

#7 Dominic Case

Dominic Case
  • Basic Members
  • PipPipPipPip
  • 1357 posts
  • Other
  • Sydney Australia

Posted 02 April 2009 - 12:48 AM

Push and pull processing are really left over from the days of black and white, or from when there was only one colour stock with one speed.

As Dirk points out, Ansel Adams book will tell you more than you ever thought you could know about variations in processing: but it's basically about black and white processing, where you get a significant shift in contrast as you vary processing times.

When it comes to colour, modern stocks are designed to be relatively immune to process variations - so you get very little contrast change, and not all that much change in negative density either. In the old days you needed to have a certain amount of density in the negative to get a decent print - an underexposed neg could be graded to print lighter, but at the expense of the blacks going grey. With longer negative processing, you'll need less print grading correction, so the blacks can stay blacker - but you don't get any more shadow detail.

So if you didn't have enough light for the stock you had, push processing was about the only option.

If you have a faster stock available it's invariably better to use that to get a faster speed.

If you aren't going directly to print, this is no longer an issue, as you can stretch the tonal range in your transfer to get the lighter tones where you want them, and retain black blacks. Still not as good as exposing properly in the first place, but that doesn't always happen.
  • 0


Visual Products

Wooden Camera

Abel Cine

FJS International, LLC

The Slider

Rig Wheels Passport

Media Blackout - Custom Cables and AKS

CineTape

Aerial Filmworks

Willys Widgets

Glidecam

Metropolis Post

Opal

Gamma Ray Digital Inc

rebotnix Technologies

Paralinx LLC

Ritter Battery

Technodolly

Tai Audio

Broadcast Solutions Inc

CineLab

Rig Wheels Passport

Opal

Ritter Battery

Aerial Filmworks

Willys Widgets

Abel Cine

Metropolis Post

The Slider

Media Blackout - Custom Cables and AKS

Visual Products

Wooden Camera

FJS International, LLC

Paralinx LLC

CineTape

Gamma Ray Digital Inc

Broadcast Solutions Inc

CineLab

Tai Audio

Technodolly

rebotnix Technologies

Glidecam