Video camera

A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in experimental broadcasts through the 1930s. All-electronic designs based on the cathode ray tube, such as Vladimir Zworykin's Iconoscope and Philo T. Farnsworth's Image dissector, supplanted the Baird system by the 1940s and remained in wide use until the 1980s, when cameras were based on solid-state image sensors such as CCDs.

Video cameras are used primarily in two modes. The first is what might be called a live broadcast, where the camera feeds real time images directly to a screen for immediate observation. A few cameras still serve live television production, but most live connections are for security, military/tactical, and industrial operations where surreptitious or remote viewing is required. The second is to have the images recorded to a storage device for archiving or further processing. Recorded video is used in television and film production. Modern video cameras have numerous designs and uses.

Any camera is a light-tight box with a hole in it. The hole allows a certain amount of light to enter the box for a certain amount of time so that it can expose, or create an image, on the light-sensitive medium we call film or CCD unit. The light is organized by the lens. The lens is a metal barrel which contains several glass elements arranged in groups. These elements gather light reflected from the scene you're photographing, focus that light, and deliver it to the surface of the film, where it can form the sharpest possible image. The barrel of the lens contains a focusing ring which allows you to focus on objects near and far. When you turn the focusing ring you are actually moving the glass elements inside the barrel in and out, varying the distance between the lens and the film. When light enters the lens, it's reflected by a mirror up through a prism and out to your eye. This makes it easier for you to focus and compose because the image you're seeing is as bright as possible. When you press the shutter release to make an exposure you trigger a whole series of events which happen at an amazing speed.

First, the lens aperture closes down to the f-stop you've selected. Second, the mirror swings up out of the way so that the light can reach the film, temporarily blocking your view. Third, the shutter opens for the amount of time you've selected, and the film is exposed. Fourth, the mirror swings back down, allowing you to see through the viewfinder again. Fifth, your lens aperture returns to wide open. You're ready to focus for your next shot.

6. Find the answers to the questions that follow:

1. What is a camera used for?

2. What are the basic principles of modern SLR camera?

3. What does the barrel of the lens contain?

4. How many modes are used in video camera?

5. Where does the camera feed real time images directly to a screen for immediate observation?

6. What makes it easier for you to focus and compose because the image you're seeing is as bright as possible?

7. What allows you to see through the viewfinder again?

8. How is the light organized?