Push processing

Push processing exists so a photographer can keep working when the light runs out. The photographer rates the film above box speed, gives every frame less exposure than the film wants, then leaves it in the developer longer to compensate.

The look is the price of that compensation. The photographer gets a usable frame in a dark room and pays with contrast, grain and dead shadows. Nothing about a push is gentle, which is why it now gets asked for on purpose.

Say the box speed and the rated speed together: 400 speed stock rated at 1600. Two stops is the common push and the one a model reads clearly. One stop is close to invisible, and three stops turns most of the frame into noise.

Name the three effects. Contrast rises and the tone curve steepens. Grain grows, clumps and spreads into the flat areas as well as the dark ones. Colour, on a colour stock, loses saturation and shifts, because the three layers do not gain the same amount from the extra development.

Say the shadows are blocked and empty and the midtones sit bright. Ask for available light only. A fill light removes the very contrast a push is there to produce.

Use it for a gig, a bar, a night street, a boxing hall or a rehearsal room. It is the honest look of a picture taken where there was not enough light to take it.

Leave it alone for a portrait that has to hold skin texture, and for anything sold on its surface. A push destroys the smooth mid tone both of those depend on.

Pull processing is the same operation run backwards. A pull rates the film below box speed and shortens development, so contrast falls and the grain tightens. A push raises both.

Cinema publishes Film Grain as its own entry at /techniques/cinema/. That entry adds grain to any picture. This one is a reason grain grows: a short exposure paid for with a long development, with blocked shadows and steep contrast attached.

Delta 3200 is a stock built to be rated high, not a process. Push processing is what you do to a slower stock to reach the same speed, and the grain is coarser when you arrive.

Push processing carried press photography through the 1960s, when Tri-X 400 rated at 1600 and developed in Acufine or Diafine was the standard answer to a night court or a boxing hall. Concert photographers kept the habit. Most black and white gig pictures from the 1970s onward are a 400 speed stock pushed one or two stops in a hired darkroom.

The model returns a clean high contrast picture with no grain in it. Say the grain is coarse and clumping, and say it is visible in the flat areas, not only in the dark ones.

The other failure is open, detailed shadows. Say the shadows are blocked and empty, and take every mention of a fill light or a reflector out of the prompt.