Video camera

a video camera is a recording device, with which the picture recordings are converted into electrical signals, contrary to the movie camera, which is based on photographic technology. For the recording of the clay/tone still another microphone must be used, which is however often already integrated.

A video camera with integrated One calls video recorders Camcorder.


Table of contents

to picture receiver

Nipkow disk

the first cameras were based on the so-called Nipkow disk. This was a round disk with approximately 30 holes in form of a spiral was arranged. If one pursues now the course of the holes, then one placesfirmly that these always scan a small, nearly rectangular range. There a hole always moves in a direction, in order to disappear at the edge. Then the next hole emerges somewhat further “down”, and scans the next line. One finds more information to this topicunder mechanical television.

iconoscope

the iconoscope (Greek) is a Fernsehaufnahmeröhre, those from Vladimir K. Zworykin was invented 1923 and the one layer from microscopically small photoelectric cells contains, which are scanned by an electron beam. The iconoscope replaced mechanical scanning procedures. Became laterthe iconoscope technology of far improved and still into the 1990er years uses.

Vidicon

the Vidicon - system works likewise with a tube and is used further for special's applications.

CCD chip

CCDs represented an important step for the reduction of video cameras.In the meantime you exceed the quality of iconoscopes clearly. With particularly high-quality cameras for this-meet the chips strongly cooled down. This makes extremely low-noise pictures possible, whose noise should be hardly perceptible after a reinforcement around 16 railways. Cheap cameras do not have a screen, but can the charge timeuse as brightness adjustment.

The more largely the surface of the assigned chip, the more lights can become “caught”. Thus the luminous sensivity of the assigned chip rises also with bad lighting conditions and the picture noise is reduced. Usual sizes are 1/6 ", 1/4 " or 1/3.4 " (1 " =2,54 cm). But caution is with thatindicated size of the chip required. The indication of pixel on the housing refers usually in the pure photo function, which number for the Filmerei is used, conceals the manufacturer gladly and even on the product sides cannot these data not be found. Also still another digital picture stabilizer comesin the play, often no longer much remains of the indicated number of pixels. Interesting is here the net pixel quantity, which is actually used for filming.

CMOS sensors

this kind picture receivers uses the Complementary Metal of oxides Semiconductor - technology. This technology was at first particularly inmuch cameras approve of to find. After the advancement taken place in the meantime it is used in addition, for fastidious tasks of observation and for the image processing. The CMOS chip takes up the picture continuously, can thus at arbitrary time be selected. The number of the pictures per second depends on it,as high the pixel frequency and the number of the pixels of the selected screen window are, lies however more highly than with the CCD chip. Individual pixels can be programmed in their functionality and be picked out individually or in groups. The dynamics (the span between the weakest and the strongest still perfectlyis appropriate for taken up signal) of the CMOS chip importantly more highly than with the CCD chip, extreme lighting situations (e.g. ligt up headlights at night in an unlighted tunnel) can be represented with so far not reached precision. Besides the CMOS technology draws by small current consumption and high picture transmission rates out (up to 300 Kb/s opposite100 Kb/s with the CCD technology). Despite these considerable advantages the CMOS technology of the CCD technology is not in every respect superior, then e.g. is. the signal-noise ratio more badly and the human viewer feels the image quality than clearly more badly, than it is accustomed this of CCD cameras. With measuring tasks (image processing)this however no role plays.

color separation

around a colored video signal to produce one needs 2 or better 3 color components.

optical color separation

the most obvious way this to produce is it to couple simply 3 picture receivers over an optics alsothe color separation takes over. Such 3-Chip-Kameras distributes the light falling by the objective over a prism on three mono chrome CCD chip. It is reached by color filters on the prism that a chip takes up the green portions, the other two red in each case and/or. blue. This procedure leads too much high-qualityPictures and one uses thus within the professional range.

sequenzielle color separation

one experimented before with sequenzieller color. A swivelling color filter should gentleman-filter alternating the 3 color components. If a same filter turns synchronously with the receiver, then also a Farbbild develops. These attempts became howeversoon adjusted. In space travel one uses such color filters still, since a great many frequency ranges are needed here.

other procedures.

With particularly inexpensive cameras however another procedure is used. There the picture receivers are used in such a way that different pixels next to one another take up different color portions.Electronics separates these portions. This leads to a poorer resolution. One of these procedures is the Bavarian sensor.

comparison 1 and 3 chip CCD procedure

after the PAL - format (American: NTSC -) On the picture monitor 720*576 pixels are represented to format. Around the completeInformation in the Camcorder to store, must have the chip 414720 *3 pixels at least. The number must be multiplied by 3, there a pixel not the complete color information, but only brightness differences to notice knows. With a 3-Chip-Modell the colors become over a prism into the portionsRed, green and blue (RGB) divided and on 3 the chips distribute. Without consideration of a digital picture stabilizer would be sufficient this number of pixels to show all necessary picture information on a picture monitor.

Since with the computation of the necessary number of pixels of the screen resolution at the television one went out (relationship720/576=1,25), which amounts to relationship actually however 4:3 =1,33, is to be counted on a higher number of pixels (768*576) of the necessary chip, square pixels presupposed.

With a 1-Chip-Modell happens the Bildspeicherung in other way. Since each CCD pixel notices only brightness differences, a color filter becomes (Bavarian filter) before each pixel either alsoGreen, red or blue set. The data processing signal becomes in the relationship 4:2: 0 (YUV - color area) noted. Y the Luma component is named, which stores only brightness differences and the color difference components (Chroma) designate U and V. That means that for each pixel the brightness and for 4 pixelsa Farbwert to be only stored. Since the human eye reacts more sensitively to brightness differences substantially than to differences in color, this reduction without large losses can be made.

Computationally a pixel quantity of 720*576*3/2=622080 results for a representation. Must be multiplied by 3, there 3 pixels foreach color are necessary. By the reduction (4: 2: 0) in the YUV Farbraum again half (division by 2) is saved.

If a digital picture stabilizer is used, the necessary pixel quantity can increase again by 60% or more.

The comparison shows, some 1-Chip-Modell quite resembles qualitiesto produce can like a 3-Chip-Modell. With the 1-Chipper even the quite complex Mimik with structure of prism is saved. With ever larger sensors, today (2004) are not chips with more than 8 million pixel in the digital photography rarity, might 1-Chipper an existence authorization quite have.

Picture stabilizer

  • electronically:

An extra large transducer chip is used, which adjusts disturbing Ruckler by shifting a smaller screen window (read window) on the large Chipfläche. The dissolution of net chip can fail however clearly smaller than from the manufacturer gladly suggested, emphasized by the large label on the Camcordergehäuse.The dissolution refers nearly in each case in the photo function; actually one wanted to film nevertheless primarily and the photo function is nevertheless rather nice accessories.

  • optically:

The optical picture stabilizer is to be preferred to digital stabilization. Here a reconciliation takes place via magnetic fields or swimming lenses, thosesensor-steered run toward the movements. Thus valuable pixel area is saved. Unfortunately the optical picture stabilizers are to be found only with Camcordern in the upper price segment.

objective

the used objective plays a not insignificant role for the achievement of good results. Therefore is here strengthened on good opticsto respect. Like already with the dissolution the manufacturers indicate gladly the digital zoom shot range, more importantly would be however the optical zoom shot factor. A too large zoom shot range also not absolutely improves the film quality. Often the wide angle range only small with most objectives is underestimated. Can throughUse of Vorsatzlinsen remedy to be created, the quality becomes however not better by such measures. In addition the automatic sharpness regulation of the Camcorders can be impaired.

to software interfaces

software interfaces between image input equipment and image processing program

SANE

TWAIN

see also

 

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