数字中间片后期制作中的色彩管理

Color Management in Digital Intermediate Post Production

在色彩管理中使用LUT具有相当大的潜在应用价值。LUT是一个简单的数据结构,它把每一个输入值映射到相应的输出值,并且还可以确定视频硬件里每帧图像中每一个像素的数据值的大小。模仿和校正LUTs提供的转换,不但能保证多种显示器之间的匹配,而且在后期制作过程中还可以使显示的图像与胶片完美的匹配。介质中呈现的色彩组叫做色彩范围。电影正片的色彩范围与数字显示器的色彩范围具有不同的特性。数字中间片(DI)工艺有2种不同的图像编码方法:一种是使用DPX文件,其作用是进行输入和输出及表示底片密度,预览画面则需要显示LUT;另一种方法是不使用LUT而直接显示图像数据。图像数据显示的是显示器的色彩范围,而不是胶片的色彩范围。在记录到胶片上之前,数据需要转换成密度值。在制作DI过程中,可以模仿洗片厂配光工序,通过调节印片光号进行的色彩校正。本文从8个方面较详细的叙述了制作数字中间片时的色彩管理。

The range of potential applications of LUT in color management is rather large. LUT, by definition, is simply a data structure which maps any input value to an output value. Within video hard- ware, LUT is also used to determine the correct intensity of each screen pixel based on the data value of each pixel in the frame. The emulation and calibration LUTs are used to provide the viewing transforma- tions which not only ensure matching multiple displays to one another, but also matching the image and film perfectly during the post productior~ The set of colors that can be represented in a medium is called the color gamut. The color gamut of motion picture print film has different characteristics than the gamut of a digital display. There are two principal methods of image encoding in the Digital Intermediate （DI） process. One uses DPX files, which represent negative film densities, as input and output. A display LUT is used to render a preview of the data. The other method works with data that is directly displayed without using a LUT. The image data represent the colors in the gamut of the display instead of the gamut of film. The data needs to be converted into density value before it is recorded into film. The la- boratory color correction with primed light adjustments could be easily simulated in the DI process. The color management during DI post production in eight areas was discusses in detail.