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The Materiality Of Video
Bernhard Frankel
The Materiality of Video
Television is a way of receiving images by radio.

To keep costs to a minimum TV was designed so that each set could be as cheap and ‘dumb’ as possible. A television image is generated by a ray sweeping through the Cathode Ray tube one line at a time. The Phosphor then glows for a moment and due to the delay in human perception the viewer sees a perfectly clear image.

This sweep can be seen if you try to take a still photograph of the screen. In the photo some of the screen, for instance, will be lit less or more than the rest of the image. This is due to the timing mismatch between the shutter speed of the camera and the sweeping build-up of the image.
(Tip: If you need to photograph a TV use a slow shutter to avoid this, or use a LCD/plasma TV.)

To broadcast images you have to define when an image starts and ends. You have to make sure that the receiver understands when a new line begins. These problems were solved by creating a broadcast standard, defining the timing of the signal and the duration of each image. The standard for PAL is that each line has a length of 52 microseconds and that an image is built up of 576 of these lines.

This means that television in its birth form was defined as a certain amount of horizontal lines and each of these lines were given a set time to sweep across the screen, this legacy is what we transfer into our computer, onto our DV tapes and onto our DVD’s.

A good introduction to broadcast standard can be found on wikipedia

A photograph of the tv screen.
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