Pushing and Pulling film?

[animefx]

I just want to make sure I understand this correctly... People talk about film having latitude for under and over exposures. Let's say I have ISO 400 film in my camera and it has "good latitude" where I can expose it at ISO 800 or ISO 1600 with reasonable results.

Well, if I'm using a 40mm f/2 lens and at 1/30th shutter then that's my limit... There is no way to "tell" the film to expose at ISO 800 or ISO 1600 it's going to expose at ISO 400 no matter what. So I assume people mean when the film is developed somewhere in the dark room it can still be brightened up to the equivalent of 1 stop or light (ISO 800) or 2 stops of light?

My Leica CL meter doesn't appear to work properly so setting the ISO on the camera really doesn't matter. I assume setting the ISO on the camera is ONLY for the meter.

How does the developer know you didn't deliberately want it a little under exposed?

I'm hoping that if I get a photo cd than the JPGs can be brightened a full stop or two without much problems. Of course the best scenario is to get a photo cd with uncompressed TIF files but I don't know what service would do that for me.

 

[SolaresLarrave]

I think pushing and pulling film are rather two different approaches to expose film, and they are both deliberate. You push film when you underexpose it on purpose, and compensate the overexposure by overdeveloping it. I have done this often, not only asking the lab to do it, but also with film I develop.

Oddly enough, you can do these processes with B&W film and with slide film. Color print film is known for having a certain latitude, which means that if there is a mistake in the exposure of a frame, the resulting print will still be satisfactory.

Take care!

 

[animefx]

Interesting... I guess I could tell the developer "keep it a little dark" or "over expose it just a little" then?

I'm wondering the average film speed seems to be asa/iso 400 if I can get away with shooting indoors with semi dim incandescent bulbs. I mean if the film has a lot of latitude will I still get acceptable results if the correct exposure would really require iso 800 film or iso 1600 film even?

 

[craygc]

As Francisco said, pushing and pulling is a deliberate and conscious decision and requests such as "keep it a little dark" or "over expose it just a little" don't really mean anything - whats a little mean? Someone has to make a qualitative decision when they compensate in development.

Generalised statements about film having a lot of latitude needs a little understanding. For example, transparency film has almost no latitude to incorrect exposure; C41 colour negs have a "lot" of latitude to over-exposure but not much to under-exposure; B&W is really about where do you want your shadows to fall on a tonal scale based on exposure in conjunction with the particular emulsion's toe and shoulder characteristics then use development to control your highlights.

How does the developer know you didn't deliberately want it a little under exposed?

I'm hoping that if I get a photo cd than the JPGs can be brightened a full stop or two without much problems. Of course the best scenario is to get a photo cd with uncompressed TIF files but I don't know what service would do that for me.

...and these comment almost suggest some confusion between the output of developing veersus a scan. A developer doesnt know what you wanted your images to look like. However, if its a defined process like E6 or C41, for tranparencies and colour negs respectively, then you will tend to get what you planned as you made the exposure (on the film). As far as scanning goes, thats a little more unpredictable as the scanner needs to make some assumptions around what to set its exposure to and often that is going to be based on an average mid tone exposure of the film, which isnt always what to shooter planned. There are ways to deal with this but it starts to move into the area of having an end-to-end calibrated workflow. However, as a caveat, although scanning and digital post-processing can to an extent correct exposure issues, this is within limited boundaries and does not negate the use of good exposure technique at the time of shooting.

In the end pushing or pulling film is going to be about wanting to derive an effect from the process or not having an appropriate speed film at the time to use. Its about knowing how far - in stops - you have moved from base and making allowances for that in development - and realising that a particular push/pull decision applies to the entire film. In contrast to this, I often shoot C41 colour negs at half their box speed and just develop normally - doing this is not pulling film.

 

[coelacanth]

Let's simplify the concept. 🙂

Imagine you have a roll of TriX. Package says the film is ISO400 speed. This means that this film is meant to be used as ISO/ASA 400 speed.

Now, if you want to PUSH it, say two stops, that means you are shooting the photos as if you were shooting with a ISO1600 film.

If you want to PULL it, say one stop, that means you are shooting the photo as if you were shooting with a ISO 200 film.

Let's talk about PUSHING 2 stops (you can apply same concept to PULLING).

You set the camera's ISO dial (if the camera has light meter like your CL) to 1600.

Forget you had ISO 400 film inside your camera. CL's light meter and YOU are now "thinking" there is a 1600 film inside.


Now, you finished the roll. If you bring the film to a lab and tell nothing to them, they'll develop the film at it's intended speed = ISO 400. That means you and your camera shot the roll 2 stops under exposed.

But if you tell the lab "I shot it at 1600" or "Please push 2 stops" then the lab will develop the film at ISO1600 speed (develop longer time) according to the specification of that film. See Massive Dev Chart for the developing time differences.

http://www.digitaltruth.com/devchart.php

Important point is that you'll have to develop for longer time (film stays in developer chemical longer time) if pushed, shorter time if pulled. Film like trix is very forgiving so even if you forget to tell lab to push, you can often get enough detail from the dark area of the shot, but the end result will be less optimal than the roll that's given enough developing time.

 

[coelacanth]

And manufactures have given this standard speed to films for a reason. A film is supposed to have the optimal tonality, fine grain, etc at this standard speed.

If you push or pull, you'll see more pronounced grain, change in contrast, etc.

Some high speed films are "pushed" by default from its "native" sensitivity. That's why some people shoot at ISO1600, 1200, or 1000 even though that film is sold as ISO3200 film to get the optimal image quality (e.g. finer grain, controllable contrast)

 

[tlitody]

Manufacturers film speeds are based on standards. The standard is different for colour neg, B+W neg and slides.
Basically the standard says how many stops of subject contrast range will give a normal print. For neg films its around 8 stops. So providing your exposure is correct and your subject has a contrast range which fits within those 8 stops, then everything will be fine when using manufacturers film speed and normal development.

So what is latitude? Latitude is the ability of film to capture a longer scale than 8 stops. B+W fims can capture as much 14 stops and more. And colour neg a little less. That means you can overexpose in normal lighting and still get useable results with normal development.
N.B. Not all B+W or colour films can do this. You have to know your films limitations discovered through trial and error.

Pushing means underexposing and over developing from normal.
Pulling means over exposing and under developing from normal.

Pushing is used for low light situations or where you want to increase subject contrast above normal contrast.
Pulling is used for very bright light scenes or where you want to reduce subject contrast to normal levels.

There's no such thing as a free lunch. You cannot push film without increasing development which in turn increases film contrast. So depending on how much you push, you will increase film contrast which reduces the useable subject contrast range. In dim light this can be a good thing but not always. But instead of getting that 8 stops of normal subject contrast, you may get 7 or 6 stops. That makes getting exposure correct more critical.

Pullng on the other hand gives much softer negative contrast. It is favoured by landscape photographers because it tends towards excellent shadow detail whilst retaining bright highlight details. But it may be too soft for a typical portrait subject.

latitude can only be used for over exposing normal contrast scenes when using normal development. But over exposure means slower shutter speeds and most people are looking for faster shutter speeds so it isn't used that much.

 

[Melvin]

B & W film forgives overexposure, so meter for the darkest part of the scene that you want to show up. Be wary of pushing film, since it mostly just increases the density of the parts of the film that already got adequate exposure. If there wasn't enough light/time to expose the film, then game over, no amount of pushing will make an image appear. In low light situations, if the choice is between fast film and fast lens, the fast lens is better(that's why slow lenses are so cheap).

 

[tlitody]

I forgot one important thing about pushing film. In dim lighting subject contrast can be low(not always). In that event pushing film can bring the film contrast back to normal. So you get a double benefit of faster film speed and normal contrast instead of low contrast result.
You have to assess the subject to determine what the result will be depending on subject contrast before deciding that pushing or pulling or normal development will work best for you.

 

[animefx]

Thanks for the informative responses guys. This is helpful.

I've made incredibly beautiful images digitally with my 5D2, I hope I'm able to do the same with film in time.

I have a roll of b&w kodak professional 400cn in my Leica CL now. I'm not sure how good my first rolls will turn out as I'm used to "shooting to the right" with digital, but I'm up for the challange.

 

[coelacanth]

Animefx,

Just FYI, 400cn is "b&w" (note quotation marks) film with C-41 process. This is basically a color negative film but "desaturated" to have only "mono" color. Because it uses chemicals for color negative film development, you cannot push or pull like traditional b/w film. It's not impossible, but because C-41 processing is automated with machine most of times, very few places accept push/pull with c-41 film and probably expensive.

Tips we've been listing are based on the assumption that you are shooting traditional b/w film.

To try push or pull, get a roll of TriX, Neopan 400 or other traditional b/w film.

Good luck.

 

[ebino]

With film you can control the contrast, during exposure and when you developing. With digital you always underexpose to save the highlights no matter what sort of contrast you're dealing with... with film pulling/pushing is not only used when ambient light is low but also in different contrast situations. on bright midday you might push the film 1 stop and process -1 in low contrast you might pull 1 stop and process +1. film can be a lot of fun that way.

In an ideal world there is no replacement for b&w film, but this not being an ideal world digital is the way to go.

 

[Juan Valdenebro]

Another comment: originally, pushing and pulling were not an unusual thing, but the common "every scene" thing... That's how B&W has worked and works the best for getting negatives that aren't too contrasty / too flat... As all scenes have different contrast, we need to expose them and develop them accordingly... "The best development time for Tri-X at ISO400" just doesn't exist: it depends on the kind of light we had on each photograph... If you meter one roll of Tri-X at 400 for sun, and another roll of Tri-X at 400 for overcast, they should be developed differently: a difference of seven minutes in my case... And if you mix both kinds of scenes (lights) in the same roll, you'll get a mix of too flat or/and too contrasty negatives... Lots of people do it, but it means mediocre negatives for lots of people... I push and pull all my film all the time depending on the scene's contrast: for harsh light shorter times and lower ISOs, and for soft light longer times and higher ISOs. The contrast of our negatives is defined with development time... The shadows detail level, with exposure...

Cheers,

Juan

 

[Roger Hicks]

ISO speeds correspond to rigid scientific standards and are the best starting point. They do NOT guarantee optimum tonality (overexposure usually gives that), finest grain (minimum exposure gives that with conventional films) or anything else much.

ISO speeds also vary with developer: a fine grain developer can drop an 'ISO 400' film to ISO 200 or less; a speed increasing developer can just about double film speed (ISO 400>650+). With C41 mono films, overexposure gives finer grain and less sharpness; with conventional film, it gives coarser grain and less sharpness.

'Pushing' means increasing development which also increases contrast (which is why it's best with low-contrast subjects). 'Pulling' is almost always a complete waste of time, unlike simple overexposure with normal deveopment. Reducing development time will reduce contrast but usually has surprisingly little effect on effective film speed.

But you'll rarely get internet 'experts' to agree on any of it because hardly any have ever studied the science behind the sensitometry. They think the Zone System is the basis of sensitometry, rather than a subset that is oversimplified in some ways and overcomplicated in others.

Cheers,

R.