Exposure

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‘Exposure’

Exposure is the basic process through which a photograph is taken. It is the exposing the light sensitive film to light, therefor burning an image to be developed. The ability to create the perfect exposure, is the ability to control the light exposure to the film.
How the photograph turns out is controlled by several factors, i.e., the intensity of the light; the sensitivity of the film; and the duration for which the film is exposed to the light. These factors all relate to each other, and thus determine if the film will be too bright, to dark, over or under-exposed.

ISO(ASA)

The first of these settings is ASA or ISO. This is the speed of the film and determines its sensitivity. For proper exposure, the ASA should always be set to the speed of the film that you are using, e.g., 400 (standard). ASA stands for American Standards Authority, and ISO stands for International Standards Organisation. These are the scales on which the films are graded. The highest grade on this scale is 3200, this being rarely used. The grain of the resulting image is effected by the ISO. It also greatly effects the contrast of the image. The lower the ISO, the more light required to correctly expose the film. Films with a high ISO can have a quicker shutter speed or a higher aperture because they require less light.

Aperture.

The aperture is another important factor of a correct exposure. It is controlled by a dial on the lens, and itself controls the amount of light let through by the lens. Similar to the iris of the human eye, the aperture opens and closes to correctly concentrate the light on the film. The scale aperture is measured on is F-stops. When the camera’s aperture is set at a high F-stop, less light is allowed into the film. This would be the correct procedure if the photograph was being taken in a bright environment. If there is little light, however, the aperture should be at a low setting so as to allow the...