The Digital Fact Book - Quantel

MTFThe Modulation Transfer Function is a measure of spatial resolving power. It can refer to amedium, such as film, ora lens, orany part of the scene-to-screen chain. It is akin to frequencyresponse in electronic images. To assess the MTF of film, it is exposed to special test imagescomprising sine wave bars of successively higher frequencies. The results on the processedfilm are assessed by measuring its density over microscopically small areas to obtainpeak-to-trough values for the different frequencies. These results should then be correctedto allow for the response of the lens, the test film itself and any D/Log E non-linearities.In a practical film system, the film images pass through many components including thecamera lens, intermediate stocks and contact printing to the projection lens. Each of thesehas its own MTF and the system MTF can be calculated as follows.MTF system = MTF1 x MTF2 x MTF3 etc…See also: Resolving powerMultimediaThe presentation of more than one medium. Strictly speaking TV is multimedia (if you havethe sound up). More typically it is pictures (moving and still), sound and often text combinedin an interactive environment. This implies the use of computers, with the significant amountof data this requires usually supplied either on CD-ROM or via a data link. ‘Surfing the net’is an example. High compression ratios are used to allow the use of pictures. One of the firstapplications was in education; now it is commonly seen at home via the Internet or DVDs.MMultimedia has a wide meaning. Another example is in the production of material which ispublished in many forms. Forexample pictures from television productions can be transferredto print for listings magazines, to EPGs and to advertising. Such transfers are commonlyhandled through networking connections.See also: ATM, MPEG, MPEG-4, MPEG-21Multiplex (Mux)Generally describes a collection of communications channels bundles into one transportsystem. For example, voice and data co-exist on a phone line carrying conversation andInternet access. In digital television ‘a multiplex’ describes a group of compressed digitalvideo channels multiplexed into single transmission stream occupying the space of oneanalog terrestrial TV channel. The term ‘Bouquet’ has also been used in this context.131