Latitude, in photographic terms, refers to the degree by which the exposure given to a film or digital sensor can deviate from the theoretically correct or optimum value and still produce an image of acceptable quality. It describes the tolerance of a photographic medium to exposure errors - both overexposure and underexposure - beyond which image quality deteriorates to an unacceptable degree through loss of highlight or shadow detail, excessive contrast, or degraded colour and tonal rendition.
Latitude is not a fixed or universal property but varies considerably between different types of photographic material and imaging systems. Colour negative film is generally regarded as having the greatest latitude of all traditional photographic materials, tolerating significant overexposure - sometimes as much as three to five stops - with relatively modest consequences, while being rather less forgiving of underexposure. This generous overexposure latitude made colour negative film a practical and forgiving choice for general purpose photography where precise exposure control was not always possible. Colour reversal film - slide film - is considerably less tolerant of exposure errors in either direction, typically requiring accurate exposure to within half a stop or less to produce a correctly exposed transparency, as the final image is viewed directly rather than through the intermediate stage of printing which allows colour negative exposure errors to be partially corrected.
Among film stocks, faster films with higher ISO ratings tend to exhibit greater latitude than slower, finer grained films. This is partly a consequence of the larger silver halide crystal structure of fast films, which responds to a broader range of exposure levels before reaching the limits of its tonal range. Slower films, while capable of delivering superior sharpness, finer grain, and richer tonal quality under correctly exposed conditions, demand more precise exposure to achieve their best results and offer less margin for error at the extremes of their tonal range.
In digital photography, the concept of latitude is closely related to dynamic range - the ability of the sensor to simultaneously capture detail in both the brightest highlights and deepest shadows of a scene. Modern digital sensors, particularly those used in professional cameras, offer impressive dynamic range and considerable latitude for exposure adjustment during post processing, especially when shooting in RAW format. However, digital sensors tend to be less forgiving of overexposure than colour negative film, as highlight detail that is clipped - driven beyond the sensor's maximum recording level - is lost entirely and cannot be recovered in post processing, making slight underexposure with subsequent shadow recovery in RAW processing a common strategy among digital photographers working in high contrast lighting situations.