The Concept of Pixels and Film Grain

The picture elements (pixels) of a digital image are usually arranged in a regular array of uniformly coloured squares as to be individually invisible. In film-based images, picture elements are sometimes randomly arranged grains or clouds of dye, also commonly called grain, in the case of all colour and some black and white films.

The values for all the pixels are collected together to create the image file - in this process, other data, such as the format or structure of the file, are also determined. Some cameras will further process the image to improve its sharpness and most also compress the image using JPEG algorithms. This, the image-processing phase, is followed by the image being recorded (written to disk or to memory).

Film grain

A random distribution of varying-sized grains and just three colours characterize the composition of colour film.

Pixel structure

The regular distribution of same-sized, uniformly coloured picture elements from a wide range of colours are characteristic of digital images.

Sensor and film in the camera

The light-sensitive element, or photosensor, in a digital camera is positioned exactly where photographic film would be located - in the lens's focal plane. A photosensor is actually superior to film in that it is perfectly flat and is in precisely the same position for exposure - something not guaranteed with film.

Film/sensor imaging

In both film and digital cameras, the lens projects an upside-down and reversed image of the subject onto the focal plane. With film, you turn the film over to view it correctly; in a digital camera, this is done by software


Steve J. Wilson is living in the United States and is a freelance writer since 2006, in digital photography related topics. If you are interested in some useful Digital Photography Classes, than you are in the right place.

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