解析数码照相机的宽容度

Latitude of Digital Cameras

在传统的银盐感光胶片中,照像宽容度是指其感光特性曲线的直线部分相对应的曝光量范围,而胶片的实际感光范围包含了特性曲线两端的足部和肩部,这与数码照相机完全不同。数码照相机的一项重要性能是其CCD传感器的动态范围。在信息传递系统中,所谓动态范围是指一个传感器响应的最大和最小信号之比,对数码照相机的CCD而言,这种响应是呈正比直线关系的,因此动态范围也表征数码照相机的照像宽容度。本文对数码照相机和传统照相胶片的宽容度进行详细的分析和对比,并提出很多在实际应用数码照相机拍摄中应注意的问题。

The photographic latitude of traditional silver salts photographic film is the exposure range corresponding to the straight line of its characteristic curve whereas the whole characteristic curve should include its shoulder and toe,thus corresponds to a much larger actual exposure range.This is quite different from digital camera with CCD sensor, where the response is proportional to the signal, alike the straight line of the characteristic curve of photographic film,so we may take the dynamic range of CCD,i.e.its maximum to minimum signal ratio,as the photographic latitude of digital camera.This paper presents a concise analysis and comparison of the latitude of digital camera and conventional photographic film and offers a series of advices very useful in the practical use of digital cameras.