Why would one push or pull a film?

[michielp]

Why would one push or pull a film? I can see three reasons:

1) To compensate for certain extreme light conditions (snow, night, etc).

2) When pushing, one can use the film in less light circumstances. So the need for a flash is circumvented.

Drawback: the film generally has a worse performance.

3) If one wants special characteristics, grain, etc. But what are these special characteristics?

Any info on point 3)?

[Keith Tapscott.]

Why would one push or pull a film? I can see three reasons:

1) To compensate for certain extreme light conditions (snow, night, etc).

2) When pushing, one can use the film in less light circumstances. So the need for a flash is circumvented.

Drawback: the film generally has a worse performance.

3) If one wants special characteristics, grain, etc. But what are these special characteristics?

Any info on point 3)?

1) Normal exposure and development is generally fine, contrast can be controlled with choice of paper grade and if necessary, some local density control at the printing stage.Changes to film development times can be used to a certain degree, but if pulled too much, it can lead to horribly flat, grey prints that a pain to print with satisfactory contrast.

2) Although certain developer types can have an effect on the emulsion speed yield, it is quite limited. Films speeds are determined at the manufacturing stage and can not be radically altered. Push processing is an attempt to rescue an under exposed film and any speed increases are moderate. It is better to use an inherently higher speed film in the first place.

3) It is not clear by what you mean by special characteristics. Please be more specific.

[Ornello]

Why would one push or pull a film? I can see three reasons:

1) To compensate for certain extreme light conditions (snow, night, etc).

2) When pushing, one can use the film in less light circumstances. So the need for a flash is circumvented.

Drawback: the film generally has a worse performance.

3) If one wants special characteristics, grain, etc. But what are these special characteristics?

Any info on point 3)?

The actual sensitivity of film cannot be changed by users (with minor exceptions such as treatment with hydrogen peroxide vapor), as it is determined at manufacture. Development can only slightly affect usable speed (no more than 1/2 stop). Some developers are less efficient in producing the image than others. Far more intelligent is to strive for optimal quality at any given film speed.

[michielp]

[quote="Keith Tapscott]
3) It is not clear by what you mean by special characteristics. Please be more specific.[/quote]

Isn't it the case that by pushing a film you get larger grains? Perhaps also some other effects show up, besides the contrast and density effects?

[Keith Tapscott.]

[quote="Keith Tapscott]
3) It is not clear by what you mean by special characteristics. Please be more specific.

Isn't it the case that by pushing a film you get larger grains? Perhaps also some other effects show up, besides the contrast and density effects?[/quote][/quote]
Yes, you will indeed get an increase in grain if that is what you are looking for, as well as increased contrast. Another method would be to use a fast film and generously expose it, then process it in print developer. Some photographers do this for `pictorial effect` although I must confess that the charm of it escapes me.
It all depends on what you are trying to acheive.

[bsdunek]

Actuelly, B&W films can be pushed two or three stops. Sometimes by longer developing times, or using a more active developer, such as Acufine or Diafine.

This is sometimes used for more grain (which will happen) or different contrast. Often, grain is a wanted thing to give a photo texture or "grit".

Play around a little - you may be pleasently suprised!

[Ornello]

Actuelly, B&W films can be pushed two or three stops.

Actually, they cannot. It's simply underexposure, for which there is no true remedy.

Sometimes by longer developing times, or using a more active developer, such as Acufine or Diafine.

'Pushing' is different from using a speed-increasing developer such as Acufine or Diafine.

This is sometimes used for more grain (which will happen) or different contrast. Often, grain is a wanted thing to give a photo texture or "grit".

Unneccessary and trite. Sharp, fine-grain images are much more aesthetically pleasing.

Play around a little - you may be pleasently suprised!

Learn how to achieve best quality and you'll be stunned.

[Keith Tapscott.]

Actuelly, B&W films can be pushed two or three stops. Sometimes by longer developing times, or using a more active developer, such as Acufine or Diafine.

Even so called speed increasing developers are limited by how far they can provide a true higher speed yield, the rest is to increase the density in an otherwise underexposed film. This effects mostly the middle and higher tones, it can not develop details in dark shadow areas if the film has not been given sufficient exposure to record those areas in the first place.
The two or three stops higher than ISO is a psuedo-speed increase, a trick that is sometimes used by press photographers when they need a higher speed film than the one in their camera and they need to record an important event there and then.
The Kodak publication (O-3) will help to explain push processing. This can be downloaded from Kodak`s website.
It is better to use a higher speed film in the first place and a film which is given optimum correct exposure and development is the one that will produce the highest print quality.