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# The Zone System

The Zone System was developed by Ansel Adams and Fred Archer in the 1940s as a method for achieving consistent results from exposing negative film all the way to paper prints. The Zone System is a framework that photographers can use to think about their photos and perform meaningful operations on them, such as altering exposure, contrast, and most all other visual aspects of a photo.

With the ZoneFinder and ZoneMapper tool, LightZone offers a unique implementation of the Zone System that has been adapted from negative film to digital media and interactive image processing allowed by modern computers. If you are familiar with the Zone System, you probably have noticed that there are differences between the traditional Zone System and LightZone.

The Traditional Zone System
The traditional Zone System was developed for negative film and has 11 zones where each zone differs by one exposure value (one "EV" which is equivalent to one f-stop). Middle (or 18%) gray falls onto zone 5. The traditional Zone System takes into account the nonlinear nature of both film and photographic paper that compresses the tonal values of highlights and shadows (the "shoulder" and "toe" of photographic media).

LightZone's Digital Adaptation of the Zone System
LightZone instead was developed for digital cameras and computers and has 16 zones where each zone differs by half an EV. Middle gray falls onto the fifth zone from the top. The reason for the differences are that digital cameras and computers use a linear representation for values of light and that computer displays have a dynamic range that is less than 8 EVs. Using half EV spacing for zones in LightZone results in 16 zones and gives the best compromise between screen space and precision.