胶片扫描仪和记录仪色彩特性及其文件格式的应用

The Color Characteristics of Film Scanner and Recorder and the Application of Its File Formats

Cineon或DPX是胶片扫描仪和记录仪常用的文件格式,它是底片密度的线性表达,并且与对数场景亮度成为线性关系,带线性场景亮度的线性编码图像格式需要较高的比特深度。扫描仪感应的不是底片密度,而是底片的透光率,透光率需转换成有意义的影像衡量单位。因为转换时有损失,所以扫描的比特深度要高于输出的比特深度,这样避免图像失真。扫描的底片图像应记录到中间片胶片上,这样避免出现多余的颗粒,胶片记录仪输出的数字中间底片必须与传统洗印制作的翻底有相同的密度范围。本文较详细的介绍了胶片扫描仪和胶片记录仪的M状态、印片密度、彩色正片密度和传感器之间的关系及其它们的彩色特性,对文件格式的正确使用、底片密度和10比特对数代码值之间的关系,进行了分析。

Cineon or DPX is the widely used file format by film scanner and recorder. It is a linear representation of negative densities and is therefore linear to log scene luminance measured in log exposure. Image formats with a linear encoding of linear scene luminance need a higher bit depth. What a scanner sees is not the negative densities but the transmittance which has to be converted to a photographic meaningful metric. Because of the loss during conversion, the scanning bit depth needs to be higher than the output bit depth to avoid aliasing.Images originating from negatives should be recorded on intermediate material to avoid additional grain. A film recorder has to produce the digital intermediate with the same density range as a traditionally created negative.The status M of film scanner and recorder, printing density, color print density, sensor andtheir relationships and color characteristics wore introduced in detail. The correct use of file formats and the relations between negative densities and 10 bit log code values were anaylised.