Wednesday, March 28, 2007


A camera is a device used to take movies (commonly photographs), either individually or in series, with or without sound, such as with video cameras. The name is derived from camera obscura, Latin for "dark chamber", an early device for projecting images in which an whole room functioned much as the internal workings of a modern photographic camera, except there was no way at this time to record the image short of manually tracing it. Cameras may work with the visual continuum or other portions of the electromagnetic continuum.
Every camera consists of a few kind of enclosed board room, with an opening or aperture at one end for light to enter, and a recording or viewing surface for capturing the light at the other end. This breadth of the aperture is often controlled by an diaphragm mechanism, but some cameras have a fixed-size aperture.
While the dimension of the aperture and the brightness of the scene control the amount of light that enters the camera during photographing, the secure controls the duration of time that the light hits the recording surface. For example, in minor light situations, the shutter rate should be slower (longer time spent open) to allow the film to capture what little light is present.
There are various ways of focusing a camera perfectly. The simplest cameras have fixed focus and use a small aperture and wide-angle lens to ensure that everything within a certain series of distance from the lens (usually around 3 meters (10 feet) to infinity) is in reasonable focus.

Friday, March 23, 2007

Satellite television

Satellite television is television delivered by means of communications satellites in geostationary orbit 37,000 km (22,300 miles) above the earth’s equator. The first satellite television signal was relayed from Europe to the Telstar satellite over North America in 1962. The first domestic North American satellite to carry television was Canada’s Anik 1, which was launched in 1973.
Satellite television, like extra communications relayed by satellite, starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are directed toward the satellite that their signals will be transmitted to, and are very large, as much as 9 to 12 meters (30 to 40 feet) in diameter. The increased diameter results in more correct aiming and increased signal strength at the satellite. The signal is received by transponders aboard the satellite, which retransmit the signal back to Earth at a dissimilar frequency. The leg of the signal path from the satellite to the receiving Earth station is called the downlink.
The satellite signal, quite weak after travelling a great distance (see inverse-square law), is together by a parabolic receiving dish, which reflects the weak signal to the dish’s focal point and is received, down-converted to a lower frequency band and amplified by a device called a low-noise block converter (LNB). Direct broadcast satellite dishes use an LNBF, which integrates the feedhorn with the LNB. A new form of omnidirectional satellite antenna, which does not use a directed parabolic dish and can be used on a mobile platform such as a vehicle, was lately announced by the University of Waterloo. The signal, now amplified, travels to a satellite receiver box through coaxial cable (RG-6 or RG-10; cannot be standard RG-59) and is converted by a local oscillator to the L-band range of frequencies (approximately). Special on-board electronics in the receiver box help tune the signal and after that convert it to a frequency that a standard television can use.

Monday, March 19, 2007

Studio cameras

Most studio cameras stand on the floor, regularly with pneumatic or hydraulic mechanisms to adjust the height, and are typically on wheels. Any video camera when used along with other video cameras in a studio setup is controlled by a device well-known as CCU (camera control unit), to which they are linked via a Triax or Multicore cable. The camera control unit along with other equipments is installed in the production control room often documented as Gallery of the television studio. When used outside a studio, they are often on tracks. Initial models used analog technology, but digital models are becoming more common. Some studio cameras are light and small enough to be taken off the pedestal and used on a cameraman's shoulder, but they still have no recorder of their own and are cable-bound.

Tuesday, March 13, 2007


Haze is an atmospheric occurrence where dust, smoke and other pollutant particles obscure the usual clarity of the sky. It occurs when dust and smoke particles build up in relatively dry air. When weather conditions block the dispersal of smoke and other pollutants they concentrate and form a generally low-hanging shroud that impairs visibility and may become a respiratory health threat. Dense haze caused by industrial pollution is also known as smog.
Sources for haze particles include farming (ploughing in dry weather), traffic, industry, forest fires and peat field fire.
Seen from afar (e.g. approaching airplane), haze is brownish, while mist is more blueish-grey. While haze is formed in somewhat dryish air, in more humid air mist is formed, and the haze particles can even act as condensation nuclei for the mist droplets.

Thursday, March 08, 2007


In optics, a prism is a transparent optical element by means of flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use "prism" typically refers to this type. Some types of optical prisms are not in fact in the shape of geometric prisms. Prisms are characteristically made out of glass, but can be made from any material that is transparent to the wavelengths for which they are designed.A prism can be used to break light up into its constituent spectral colors (the colors of the rainbow). They can also be used to reflect light, or to split light into components with different polarizations.

Sunday, March 04, 2007

The Great Wall of China

The Great Wall of China is a sequence of stone and earthen fortifications in China, built between 5th century BC and the 17th century to guard the northern borders of the Chinese Empire for the period of the rule of successive dynasties. Several walls, referred to as the Great Wall of China, were built since the 5th century BC, the most well-known being the one built between 220 BC and 200 BC by the first Emperor of China, Qin Shi Huang; this wall was situated much further north than the current wall built during the Ming Dynasty, and little of it remains.
The Great Wall is one of the existing megastructure and the world's longest man-made structure, stretching over 6,352 km (3,948 miles) from Shanhai Pass in the east to Lop Nur in the west, along an arc that about delineates the southern edge of Inner Mongolia.