Essay: Video technology

In this essay I will compare and contrast different forms of video technology from the past, to the more advanced technology that our current era has introduced. I think that video technology has developed significantly over the years and I prefer the digital technology.

The first movie cameras created used celluloid technology. This kind of movie camera captures a series of photographs on to a strip of plastic film every time the shutter opens and closes. In a standard film camera, you have to wind the film on so it advances to the next position to capture another photograph. But in a celluloid camera, the film is constantly moving and the shutter is constantly opening and closing to take a continuous series of photographs at approximately 24 times per second. The unexposed movie film starts out on the large reel at the front of the camera. The film then passes over guide and spring pressure rollers that hold it firmly against the central sprocket. The teeth of the sprocket then lock into the holes on the edge of the film and pull it precisely through the mechanism. Light then enters through the lens and passes into a prism. Some of the light continues on through the shutter and hits the film, exposing a single frame of the movie. Celluloid cameras were extremely expensive to purchase. There for, only large film companies with excessive budgets used them.

When video recording was invented, photographic film was replaced by magnetic videotape, which was simpler, cheaper, and needed no photographic developing before you could view the things you’d recorded. Tape recording differentiated from celluloid in the fact that instead of plastic film, magnetic tape was used to expose film. 1975 saw the introduction of two superior formats of video technology. VHS, produced by JVC and Betamax, produced and developed by Sony. These two revolutionary tape recorders were battling it out throughout the 70’s to early 80’s for a permanent place in the growing market of film. However, only one would come out on top’ Betamax had a hold over VHS in the early stages due to its cassette size and video quality. Betamax’s smaller-sized cassette limited the size of the reel of tape and there for couldn’t compete with the VHS two hour capability and Instead, Sony had to slow the tape down to 0.787 ips in order to achieve two hours of recording in the same cassette size. This reduced Betamax’s once-superior video quality to worse than VHS when comparing two-hour recording. Sony finally released an extended Beta cassette which allowed Betamax to extend the two-hour limit. However, by then VHS had already reigned supreme and defeated their rival.

Modern electronic camcorders use digital video. A charge-coupled device is used to convert what the lens sees into digital format. In other words, each frame is not stored as a photograph, but as a long string of numbers that describe each detail of pixels that the image contains. Digital cameras look very similar to celluloid cameras however, they are completely different. When you press the button to take a photograph with a digital camera, an aperture opens at the front of the camera and light streams in through the lens. There is no film in a digital camera. Instead, there is a piece of electronic equipment that captures the incoming light rays and turns them into electrical signals. Light from the object you are photographing zooms into the camera lens and this incoming image hits the CCD, which breaks it up into millions of pixels. The CCD measures the colour and brightness of each pixel and stores it as a number.

Colour temperatures are an integral part of cinematography. Every light source has its own colour which is measured in Kelvins. It varies from red to blue, red symbolising a warm, tungsten light and blue resembling a cooler colour. Kelvins range from 0k to 8000k with red and blue being at opposite ends of the scale. Tungsten light will be located between 1000k and 3000k on the scale with cooler colours found above 7000k. Cameras use white balance to control colour temperature with modern cameras coming installed with an automatic white balance. However, it can also be set manually. Another way to combat temperatures is to contrast light, for example by adding warm, tungsten light to a room that has a large amount of blue light coming through. This can work both ways.

The aspect ratio is the proportion between the width and the height of a picture. It is often expressed in the W:H format. ‘W’ meaning width and ‘H’ meaning height. Most televisions and computer monitors currently available have an aspect ratio of 16:9, which fits perfectly in the high definition television shows. However, movies are usually filmed with a ratio of 21:9, which will results in black bars at the top and bottom of the picture.

In the 1980’s, shooting and editing movies became slightly more complicated with the introduction of VHS, VHS-C and Betamax. You could read a two page article and know the differences between competing two formats. When digital came on the scene everything went out the window. Suddenly there was a wide range of video formats including wmv, asf, rm, mov and mpeg. Video compression software works by looking for redundancies in a frame and representing them together. At extremely high rates of compression this becomes obvious, however, at minor rates it’s hard for people to notice. There is a risen desire in every movie maker to try to use lossless formats, which reserve all the original data, but the compression ratios aren’t good enough to make them practical. Choices at the moment are to use the highest quality compression available for your intended purpose and to have multiple versions of your files for multiple uses. For example, one file for web-streaming, another for disk-based distribution, another for standard definition DVD, another for Blu-ray, etc. The highest quality video format is going to be the format you captured your video in. While digital files do not degrade in quality during copying, every time they are compressed with a ‘lossy’ compression they lose data, so converting your uncompressed DV formatted files even into a high quality MP4 will result in a loss of quality.

Satellite television is a system of supplying television programming using broadcast signals relayed from communication satellites. The signals are received from an antenna, referred to as a satellite dish. A satellite receiver then decodes the television programme for viewing on a television set. There are two types of receivers, an external set top box and a built in television tuner. Satellite TV provides a wide range of channels and services. The direct broadcast satellite television signal can be either analogue signals or new digital signals, both of which require a compatible receiver. Digital signals may include high definition television. Some channels are free to view, however other channels you may need to pay a certain sum of money for a subscription.

Broadcasting is the way in which television receives their signal from TV channels. Broadcasting is the process in which transmitters send codes and signals for the TV to receive, and then transfer the signal into a visual output. The first form of broadcasting was analogue. Analogue uses radio waves to transmit audio, video coding and signal which contained the brightness, colours and sound. The signal is received through the antennae on the TV. The code is then transferred into lines by the CRT box in the television and the lines are beamed rapidly across the screen to create a picture. The transmission comes from big TV bases and transmitted to homes around the region and other smaller transmitters throughout the country. However, there are variables such as weather and problematic terrain which may affect the signal.

Source: Essay UK - http://doghouse.net/essays/information-technology/essay-video-technology/


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