Why push/pull film

[pinchers of peril]

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As I've learned more about film photography I hear a lot of people talking about pushing/pulling film.  Is the main advantage of pushing film to get fast shutter speeds?  I had read that it can increase contrast but also increases the grain in the image.  Just curious for those of you who push your film what is your reasoning.  Also why would you ever pull film? it seems like pulling only leeds to undesirable things like slower shutter speeds and less contrast.  Thanks.

[madNbad]

Many users will expose film at one half to a full stop below rated box speed for a denser negative and better tonal range.  The trade off being a slower shutter speed or a larger aperture.  Prior to the digital revolution there wasn't any choice if you wanted a higher ISO so a whole matrix of exposure and development was used to to achieve the desired results.  Both pushing and pulling can result in reciprocity which can affect the final negative by unwanted shifts in color or tone due to lengthening or shortened exposure times.  An excellent book is "The Negative" by Ansel Adams as it gives insight of how and why light works on film.  The only way to know how a film wil react is testing.  Sometimes tedious and boring but test rolls on a color wheel or grayscale will give you the hard results and a better idea of what to expect.  Good luck with your adventures with film.

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[TomB_tx]

We get spoiled today with the high ISO speed of digital. In college in the mid 1960s my normal films were Kodachrome II at ASA (now ISO) 25, and for B&W Panatomic X at ASA 64. For available light work (no flash in dim light) every edge was needed, including fast lenses and pushing development. For events even TriX at 400 was marginal for action, so my standard was to expose TriX at 1200 and develop in Acufine, and sometimes to use 2475 recording film. Highest speed color available was 160.

We thought we had it good, as not many years before Kodachrome was 10, and high speed B&W was 125. Pushing was mandatory.

[Tony Mac]

From your other thread it looks like you like shooting Portra 400. With that film technology and how far along it's come, you really don't need to do much for it to look great. Most people tend to shoot that film with an EI of 200-320 to make the negative more dense as @madNbad said. Then just have your lab process normally, it should look great. Any other tonal adjustments you can do digitally after it's scanned. Or you can have your lab do it during the scan.

[too old to care]

I am one of those that shoots film one or more f-stop over.  I have done this since the 60's, not to get faster shutter speeds, but to ensure that I get a usable negative.  One too dense is much better than a thin one.  I never pushed film to get higher shutter speeds, just swapped for a higher ISO film, or used a bigger lens.  But, like others have said, it is one way to increase shutter speeds.  

 

Wayne 

[finarphin]

Pushing or pulling is the main way to adjust the density of the negative to the range in tone of the subject.  Eyes and brain do it one way, and the photographer has to do it manually, so to speak.  As MadNbad observes, Ansel Adams gives a good explanation in his book.  The subject might have a range in tone of 1:4, in which case you would want to push, or it could have a range of 1:1000, in which case you would want to pull.

[wattsy]

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Pushing and pulling film is traditionally about altering development as well as exposure. In other words, shooting a film slower than box speed (e.g. Porta at ISO 200, as seems the fashion at the moment) and developing as if normally exposed, simply overexposes the film (often to nice effect) and is not the same as pulling the film (where both exposure and development are typically adjusted together to reduce contrast). Similarly, shooting Tri-x at ISO 800 simply underexposes the neg unless development is also pushed to compensate for the underexposure.

Edited September 14, 2015 by wattsy

[philipus]

Also why would you ever pull film? it seems like pulling only leeds to undesirable things like slower shutter speeds and less contrast.  Thanks.

 

Over-exposing a colour negative roll 1 or 2 stops will have benefits if one scans, depending on the scanner used. Over-exposure will give more exposure of the shadow areas (longer times) which will scan better and with less annoying colour noise. One may think that this would blow highlights beyond repair but that's not the case; on C41 highlights are virtually always possible to "pull down" to obtain detail (it's surprising how much is there). Of course, this may not be necessary 1) if one uses certain scanners other than for instance the Nikon Coolscans which tend to cause such colour noise, 2) one has post-processing skills to deal with the noise (not very complex), or 3) don't really care about this at all (which is of course completely OK). I realise this is somewhat off-topic but thought I should mention it.

 

Edit: About slower speeds. I tend to shoot ISO 400 rolls at 100 and 160 rolls at 80. In most contexts, daytime and indoors until early evening, it's possible to shoot at acceptable speeds if one over-exposes like this. For darker settings one can for instance use the excellent Portra 800 if one wants to over-expose a stop or so to tame shadows for the purposes of scanning. Then again, it all depends on one's preferences. Oh, and since the roll should be developed at box speed by the lab, one can of course change the ISO during a roll. For instance, on a contrasty day one may perhaps want to over-expose an ISO 400 roll two stops to deal with the sharp shadows but as the day gets darker one may want to revert to box speed.

Edited September 17, 2015 by philipus

[BerndReini]

Push processing affects mostly the highlights, while overexposure affects mostly the shadows. Ansel Adams's Zone System explains all this in detail, but it refers mainly to black and white film. I agree that the new color negative films are best overexposed slightly, then processed normal and dealt with during scanning because their latitude is so great.