The film speed indicates relative sensitivity to light and is expressed as an ISO-speed number. The higher the number, the more sensitive-the faster-the film; the lower the number, the less sensitive-slower-the film.

Fast films require less light than low-speed films for proper exposure. Graininess and sharpness are generally best with low-speed films. Graininess is the sand-like granular appearance given to an image by the structure of the film's light-sensitive emulsion. As film speed increases, graininess increases.

However, with modern film technology, a high-speed film such as KODAK GOLD 400 Film can now produce excellent photographs with a minimum of graininess, making it a great all-purpose film. ISO 25 speed films are extremely fine grained and ideal for big enlargements. At the other end of the scale, ISO 1,000 speed films allow for pictures in low-light situations, extended flash range, and stopping fast action using adjustable cameras.

Kodak and Gold are trademarks.