Color space
The color range between specified references. Typically three references are quoted in television: for example RGB, Y R-Y B-Y and Hue, Saturation and Luminance (HSL) are all color spaces. In print, Cyan, Magenta, Yellow and Black (CMYK) are used. Film is RGB while digital cinema uses X´Y´Z´. Moving pictures can be moved between these color spaces but it requires careful attention to the accuracy of processing involved. Operating across the media – print, film and TV, as well as between computers and TV equipment – will require conversions in color space. Modern digital techniques allow the use of both RGB and Y R-Y B-Y to best suit production requirements. See also: 2K, Keying
Color Transform Language (CTL) Color Transformation Language is a small programming language designed to serve as a building block for digital color management systems. It allows users to describe color transforms in a concise and unambiguous way by expressing them as programs that describe the transform that can be applied to pixel data. It is designed to run fast, operating on many pixels at one time. See also: OpenEXR Website:
http://ampasctl.sourceforge.net
CMOS
Complementary metal–oxide–semiconductor technology very widely used to manufacture electronic integrated circuits (chips). Recently the application of CMOS technology to image sensors has increased. The chips are cheaper than the alternative CCDs, they consume less power, can be more sensitive (faster), have less image lag and can include image- processing functions on the sensor chip.
Color management
The management of color through a process – such as DI or video grading. Television engineering folklore says that a picture never looks exactly the same on two picture monitors. By the use of probes to measure the colors on a screen, and equipment with adjustable color LUTs, the look of color can be set to the same across all monitors – within their technical limits. Such care is needed in DI where grading is a big part of the process. Today DI suites may be equipped with a digital projector and large screen. The look of colors on the screen can be set to match those expected for a chosen print stock, so the DoP and grader can see the footage exactly as it will look in the cinema, or other chosen audience. See also: WYSIWYG, X´Y´Z´
Color timing (a.k.a. Grading) The color of film exposed and processed in a laboratory is controlled by separately altering the amount of time that the red, blue and green lights are used to expose the film. This is referred to as color timing and its effect is to alter contrast of R,G and B to create a required color balance. In a lab, color timing is usually applied at the point where the edited negative is copied to the master interpositive but can be done later at other points if required. In the digital film process, color timing is applied at any required time, as required. In addition there is far more flexibility for color control with gamma, hue, luminance, saturation as well as secondary color correction. In addition, the results can be seen immediately and projected onto a large cinema screen and further adjusted if required. See also: Grading, Lights, Timing C Common Image Format (CIF) The ITU has defined common image formats. A standard definition image of 352 x 240 pixels is described for computers. For HDTV production the
HD-CIF preferred format is defined in ITU-R BT.709-4 as 1920 x 1080, 16:9 aspect ratio with progressive frame rates of 24, 25 and 30 Hz (including segmented) and interlace field rates of 50 and 60 Hz. This has helped to secure the 1920 x 1080 format as the basis for international program exchange. See also: ITU-R BT.709
Component video The normal interpretation of a component video signal is one in which the luminance and chrominance remain as separate components, e.g. analog components in Betacam VTRs, digital components Y, Cr, Cb in ITU-R BT.601 and 709. RGB is also a component signal. Pure component video signals retain maximum luminance and chrominance bandwidth and the frames are independent of each other. Component video can be edited at any frame boundary. See also: Cut (edit)
Composite video
Luminance and chrominance are combined along with the timing reference sync and color burst information using one of the coding standards – NTSC, PAL or SECAM – to make composite video. The process, which is an analog form of video compression, restricts the bandwidths (image detail) of the color components. In the composite result color is literally added to the monochrome (luminance or Y) information using a visually acceptable technique. As our eyes have far more luminance resolving power than for color, the color sharpness (bandwidth) of the coded signal is reduced to well below that of the luminance. This provides a good solution for transmission and viewing but it becomes difficult, if not impossible, to accurately reverse the process (decode) back into pure luminance and chrominance. This limits its use in post production as repetitive decode, recode cycles severely impair the pictures. Deriving keys from composite video gives poor results. See also: 4fsc, D2, D3
Compositing
Multi-layering for moving pictures. Modern composites often use many techniques together, such as painting, retouching, rotoscoping, keying/ matting, digital effects and color correction as well as multi-layering to create complex animations and opticals for promotions, title sequences and commercials as well as in program content. Besides the creative element there are other important applications for compositing equipment such as image repair, glass painting and wire removal – especially in motion pictures. The quality of the finished work, and therefore the equipment, can be crucial especially where seamless results are demanded. See also: Digital keying, Photo-real
Compression (audio)
Reduction of bandwidth or data rate for audio. Many digital schemes are in use, all of which make use of the way the ear hears (e.g. that a loud sound will tend to mask a quieter one) to reduce the information sent. Generally this is of benefit in areas where bandwidth or storage is limited, such as in delivery systems to the home, handheld players, etc. See also: Auditory masking, Dolby Digital
Compression (video)
The process of reducing the bandwidth or data rate of a video stream. The analog broadcast standards used today, PAL, NTSC and SECAM are, in fact, compression systems which reduce the information contained in the original RGB sources. Digital compression systems analyze their picture sources to find and remove redundancy both within and across
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GLOSSARY OF TERMS
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