be anything from a PC to a super computer. Also some applications are mutually exclusive – when the computer’s hardware is configured for one it has to be re-configured to run another. It is then arguable whether this is still a standard platform or has it metamorphosed into a dedicated system?

Standards (television)

A digital television standard defines the picture format (pixels per line and active lines), vertical refresh rate and whether the vertical scan is interlaced or progressive. For example, European SD digital television is 720 x 576/50I, and an HD standard is 1920 x 1080/30P. See also: Format (television)

Standards conversion

A B C D E F G H I J

K L

M N O P Q R S T U V

W X Y Z

Changing the standard of existing television material that may involve two processes (four if going from and to analog coded systems such as PAL and NTSC). The two main processes are format conversion to change the spatial (horizontal and vertical) sizes of the pictures and changing the vertical scan rate – the number of pictures per second. For broadcast applications this needs to be completed retaining the maximum possible fidelity of the input content. The re-sizing process involves the relatively straightforward task of spatial interpolation – spreading the information from the original pixel array over a different pixel structure. Note that the crude method of dropping or repeating lines/pixels will give very poor results and the detail of the interpolation process used is important for best results. The second process is more complex as, changing the number of frames or fields per second (temporal conversion) means creating new ones or removing some – preferably without upsetting any movement shown in the pictures, so simply repeating or dropping fields or frames will not do. For this the movement within the pictures has to be analyzed so that ‘in-between’ pictures can be synthesized. This is a very specialized area and there are highly developed techniques used on the best modern standards converters that do this very well, but never perfectly. See also: Format (conversion), Frame-rate conversion

Statistical multiplexing (a.k.a. Stat Mux) This increases the overall efficiency of a multi-channel digital television transmission multiplex by varying the bit-rate of each of its channels to take only that share of the total multiplex bit-rate it needs at any one time. The share apportioned to each channel is predicted statistically with reference to its current and recent-past demands. For example, football – generally with much action and detail (grass and crowds) – would use a higher data rate than a chat show with close-ups and far less movement. The data streams for each program are monitored and their bit rates varied accordingly to fit the bit rate of the whole multiplex. See also: Variable bit rate

Status M and Status A See: Densitometer

StEM

Standard Evaluation Material was created by the ASC (American Society of Cinematographers) and DCI in 2004 to assess the quality of possible digital cinema compression systems and formats against the best that film can offer. It is about 25 minutes of material from multiple film formats.

Stereoscopic Window (Stereoscopic) The amount of stereo image available to the viewer is dictated by the frame surrounding a stereoscopic image, e.g. the size of TV or projection

screen. This boundary is called the Stereo Window. Depending on their parallax objects will appear either in front, at or behind this window. IMAX has the largest window.

Stereoscopy The process of making and presenting images using ‘left eye’ and ‘right eye’ cameras. The resulting ‘left eye’ and ‘right eye’ stereo images allow audiences to perceive depth into and out of the screen. Although the technique can add greatly to the viewing experience and is often referred to as ‘3D’, viewers cannot look around objects – as would be the case with real 3D. In stereoscopy, presenting objects from the left and right eyes’ point of view in the same way that our eyes would look at them in the real world creates the depth effect. If the left and right eye images of an object are coincident at the screen, then it appears to be at the distance of the screen. If the left and right images on the screen are crossed over, with the right image on the left and the left image on the right, then the object appears to be in front of the screen as our eyes converge on the images. If the left and right images are not crossed over but closer together than the distance between our eyes (interocular distance generally taken as 63.5 mm for the average adult), then the object appears to be behind the screen as our eyes converge less. To show an object at infinity left and right images are shown spaced by the interocular distance. The advent of digital media replacements for film has sparked the development in new shooting technologies that can be capable of making live 3D TV. But generally post production is needed to correct unwanted differences between left and right cameras and to finesse the point of view and perspective. Now 3D cinema can be experienced at almost any digital cinema – not just at the big venues. A viewing system is required that can sequence the images into the correct eyes, such as Real D, Dolby or McNaughton. These require wearing glasses that are passive polarized (Real D), passive frequency based (Dolby) or active switched (McNaughton). Live shooting and easy exhibition means that live events can be shown on cinema screens – giving audiences a new experience and theatres a potential new revenue stream. For television, 3D screens have been developed but are now only just being mass-produced, partly due to the lack of 3D material! NHK Technical Services (NTS) has produced sets that use filters on the front of the screen and so can be watched without glasses. See also: 3D

Stop

A ratio of amount of light where one stop represents a x2 change – doubling or halving of the amount of light. The operating range of film and electronic light sensors, such as CCDs and CMOS, are quoted in stops. Typically, a camera’s shutter speed and the lens’s aperture setting restrict the light arriving at the sensors/film so the mid brightness of the required scene corresponds to the middle of the sensor’s or film’s sensitivity range. Stops are simply the expression of a ratio, not absolute values. As they represent doubling or halving of light, they are actually powers of 2. So 1 stop = x 2 2 stops = x 4 3 stops = x 8

4 stops = x 16 etc.

Note that cine lenses are often marked in f-stops (white) and T-stops (red). The former is a geometric relationship between focal length and aperture and does not take into account how much light is lost within a lens. T-stops do and represent the real working values. So, on a lens that loses a full stop in transmission (i.e. a 50-percent loss), f/8 would result in the same exposure as T11. F and T values are usually close on prime lenses but zoom lenses show a greater difference.

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GLOSSARY OF TERMS