gamma

One of the constants that express the characteristics of photographic materials. It is defined as the gradient of the straight line portion of the photographic characteristic curve. It is also called the development coefficient. It is related to the tonal gradation and latitude of a photograph and is generally small for highly sensitive materials, while at the same time the tonal gradation and latitude are large. On the other hand, to obtain an image with high contrast, such as in photographs for platemaking, materials with a high gamma are used. The value of gamma varies depending on the material as well as the developing conditions. That is, in addition to depending on the type of developer, increasing the development time and temperature increases gamma.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

写真材料の特性を表す定数の一つ．写真特性曲線の直線部分の勾配で定義される．現像係数ともいう．写真の階調性や寛容度に関係し，一般に高感度材料では小さく，同時に階調性，寛容度は大きい．一方，製版用写真のようにコントラストの大きい像を得るには，ガンマの大きい材料を用いる．ガンマの値は材料のほか現像条件によっても変わる．すなわち，現像液の種類に依存するほか，現像時間，温度の増大はガンマを大きくする．

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