Apple MA261Z/A User Manual - Page 832

Whites In the Final Cut Express HD color correction filters, most of the controls that you use to correct your clips affect the whites. Whites Whites make up the maximum range of luma in your clip. On this gradient, controls that affect the whites affect the rightmost three-fourths of the gradient, from gray to white. The effect that controls have over the whites of an image start to diminish at approximately 25 percent luma, shown above. This excludes the darkest parts of your image. When you use controls that affect only one of these ranges, all changes made to the hue, saturation, and luma levels of your picture happen exclusively in the area that falls within that particular range of luminance. This allows you to perform very targeted color correction only where it's needed, such as subtly manipulating the hue of the highlights without touching the shadows, or vice versa. Illegal Broadcast Levels Broadcast facilities have limits on the maximum values of luma and chroma that are allowable for broadcast. If a video exceeds these limits, distortion can appear in the form of colors bleeding into one another, the whites and blacks of your program washing out, or the picture signal bleeding into the audio and causing audible distortion. In all these cases, exceeding standard signal levels can result in unacceptable transmission quality. For this reason, as you are performing color correction on clips in your edited sequence, you need to make sure that the luma and chroma levels of your video stay within the parameters referred to as broadcast legal, or acceptable for broadcast. 832 Part IX Effects