Push and Pull Processing: Shooting Film Above or Below Box Speed

Pushing film means rating it at a higher speed than the box says and developing it longer to compensate. Pulling is the reverse. Pushing gets you usable pictures in light too dim for your film; pulling tames contrast or rescues overexposure. Both change how the negatives look, and both apply to the whole roll.

What pushing actually does

If you rate ISO 400 film at EI 1600, you underexpose it by two stops. Extra development then builds more density in the midtones and highlights, bringing them up to a printable level. What it cannot do is create detail in the shadows that received too little light to form a latent image. The result is a negative with higher contrast, emptier shadows and more grain.

Pushing is a trade: you gain shutter speed and lose shadow detail. In dim, contrasty light like a concert or a night street, that trade often looks great. In flat light it can look harsh and empty.

Push and pull in stops

Box speed	Pull 1	Normal	Push 1	Push 2	Push 3
ISO 100	EI 50	EI 100	EI 200	EI 400	EI 800
ISO 400	EI 200	EI 400	EI 800	EI 1600	EI 3200

How much to change development

Always start from the film's data sheet or a development chart, which often list push times directly. Without them, common starting points for black and white film are:

Push 1 stop: increase development by about 25 to 40 percent.
Push 2 stops: increase by about 50 to 80 percent.
Pull 1 stop: reduce by about 20 to 30 percent.

Some films push far better than others. Tri-X 400 and HP5 Plus are famous for pushing to 1600 and beyond. Delta 3200 and T-Max P3200 are designed for it. Speed-enhancing developers such as Microphen, DD-X and T-Max Developer give better shadow detail when pushing; see film developers.

Pushing color film

C-41 color negative film can be pushed by extending the developer time. Labs usually charge a small fee per stop. A one-stop push with Portra 400 or Cinestill 800T works well; two stops starts to show color crossover, muddy shadows and grain. Slide film in E-6 pushes more cleanly than negative film, which is why pushing chromes was routine for sports and news photographers.

Pulling film

Pulling reduces development to lower contrast. It is useful in very harsh light, for compressing a high-contrast scene, and for rescuing film exposed at too low a speed by mistake. Pulled film has softer contrast, finer grain and good shadow detail because those shadows received extra exposure. It is the roll-film cousin of N-1 development in the Zone System.

Telling your lab

Mark the canister or roll clearly, for example "+2" or "push 2 / EI 1600," and tell the lab when you drop it off. Many photographers write it on a piece of tape on the cassette before they even start shooting the roll, so it can't be forgotten. Find labs that push and pull in the directory of developing labs.

When a roll is mixed

Because the whole roll gets one development, avoid changing EI mid-roll. If you must, develop for the speed used on the most important frames. Black and white negatives are forgiving: a roll shot partly at 400 and partly at 800 developed for 800 usually prints fine, with denser frames from the 400 section.