ABSTRACT
True speed increase versus pushing A film’s speed rating indicates its ability to record shadow detail A true speed increase therefore means that the film can record shadows with less exposure. It is almost impossible to achieve more than a one stop true speed increase over a manufacturer’s ISO rating, in spite of claims by countless products. The simple reason is that film manufacturers use every technique possible to increase the speed of modern films. There is not much more that can be done! There are, however, three effective methods for increasing speed with modern films:
■ hypersensitization before exposure ■ latensification after exposure ■ special developer techniques or additives
Pushing film means underexposing and overdeveloping. Overdevel opment produces greater density in the midtones and highlights, but little increase in the grossly underexposed shadows. The result of pushing film is:
■ a maximum 2/3 stop increase in shadow density ■ a 1 to 4 stop increase in midtone and highlight density ■vastly increased grain and contrast There are two reasons to push film: (1) hand held practicalities and
(2) aesthetics. Pushing lets you make tenable exposures in low light situations. For example, if your meter reads f/2.8 at 1/8 of a second for a normal exposure, you may have to underexpose by two stops to make a hand held exposure at f/2.8 at 1/30 of a second.
