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Matakuliah : O 0382 – Dasar-dasar Produksi Siaran Televisi Tahun : 2010 THE TELEVISION CAMERA (2) Pertemuan 4
Electronic Characteristics (1/8) Electronic Characteristics There are common electronic characteristics to all television cameras: (1) aspect ratio, (2) resolution, (3) frame rate, (4) light sensitivity and operating light level, (5) gain, (6) video noise and signal-to-noise ratio, (7) image blur and electronic shutter, (8) smear and moiré, (9) contrast, (10) shading, (11) white balance. Aspect ratio As explained previously, the most noticeable changes from traditional 4 x 3 aspect ratio into digital HDTV 16 x 9 aspect ratio will affect the output of picture quality or the image resolution. 3
Electronic Characteristics (2/8) Resolution Refers to measuring detail in the picture and is the major factor that distinguishes standard television from HDTV pictures. The quality of television is determined by the degree of resolution of the video it produces. The picture resolution a camera can produce depends on: (1) the quality of the lens, (2) the number of pixels of the CCD, and (3) the general signal processing. A camera with a single CCD produced by necessity lower-resolution pictures than the three-chips cameras. The resolution of the picture seen on TV depends on the videotape recording system, the transmission system, and of course the television set. In print, resolution is measured in dpi (dot/ pixels per inch). CCDs are 4 usually measured by the total number of pixels.
Electronic Characteristics (3/8) Frame rate Refers to the number of complete video frames the video system produces each second. The frame rate is important not only for specifying the quality pictures the camera produces but also for the compatibility of the camera with the utilized recording system. The standard NTSC television scans 30 frames per second (fps). The 480 p and 720 p scanning systems normally have a frame rate of 60 fps but possible to have variable frames – especially if used for electronic cinema productions. The standard 1080 i HDTV system has a frame rate of 60 fps. 5
Electronic Characteristics (4/8) Light sensitivity and operating light level Light is used to produce a video signal when the camera imaging device is converting light into electricity, and the light requirement depends on the light sensitivity of the imaging device. The minimum operating light level under which cameras perform adequately is determined by how much light the camera lens admits and how much the video signal can be boosted electronically before the picture begins to deteriorate. Gain is when a camera can produce pictures in extremely low light levels because it has the ability to boost the video signal electronically. In studio cameras, the gain is adjusted through the CCU. In ENG/ EFP cameras, it is controlled by a gain control switch. 6
Electronic Characteristics (5/8) Video noise and signal-to-noise ratio The word ‘noise’ refers to the audio field and applied to unwanted interference in video. The ‘noisy’ pictures can be recognized by the amount of white or colored vibrating spots or artifacts that appear throughout an image and cause it to become less distinct. If the picture signal is strong (mainly because the imaging device receives adequate light), it will cover up the snow and the S/N ratio is desirable. (S/N ratio is signal-to-noise ratio – a relationship between signal and noise). If the picture signal is strong then the signal is high (strong picture information) relative to the noise (picture interference) under normal operating conditions. 7
Electronic Characteristics (6/8) Image blur and electronic shutter The image blur has become one of negative aspects of CCD imaging device. In order to avoid this blur, the CCD cameras are equipped with electronic shutter. Electronic shutter will control the amount of time that light is received by the chip. The slower the shutter speed, the longer the pixel of the CCD imaging surface are charged with the light of the object and the more the object will blur. Smear and moiré Smears show up adjacent to highlights as dim bands that weave from the top of the picture to the bottom. Digital cameras with high-quality CCDs are practically smear-free. Moiré interference shows up in the picture as vibrating patterns of rainbow colors. 8
Electronic Characteristics (7/8) Contrast is expressed in ratio. Contrast is the relatively limited range between the brightest and darkest picture areas the video camera can reproduce. The normal contrast ratio is 40: 1 or 50: 1 which means that the brightest picture area can be only forty or fifty times brighter than the darkest one for optimal picture. If a scene exceeds a camera’s contrast range, however, either the video operator or automated circuits in the camera will adjust the picture so that it does fall within the contrast tolerance of the pickup device. Shading An activity when the video operator adjusts the picture to optimal contrast range. 9
Electronic Characteristics (8/8) White balance The compensation conducted by the camera when the camera compensates for the reddish or bluish light to pretend that the camera is dealing with perfectly white light. In the studio, the white balancing is usually conducted by video operator who adjusts the RGB channels at the camera control unit. When operating a studio camera, you will be asked by the VO to zoom in on the whitebalance card in the primary set area and remain on it until the white balance is accomplished. How to white balance: - Focusing on a white card, piece of form core or other white object that is illuminated by the lighting in which the performance will take place; - Zoom in the card until it fills the entire screen (view finder); - Press the white balance button and wait until the view finder display 10 indicates a successful white balance, and redo the steps each time you encounter a different lighting situation.
Operational Characteristics (1/5) Operational Characteristics There are less fewer button and switches owned by studio camera compared to ENG/ EFP camcorder or a consumer camcorder. It is because the studio camera is remote-controlled by its camera control unit and it is the VO who works on all buttons during the production for optimal picture quality. On the other hand, the ENG/ EFP cameras and consumer camcorders are self contained: have all switches and buttons on the camera and the users can ready the camera and keep the camera operational during the entire shoot. Furthermore, the automatic control ENG/ EFP cameras and consumer camcorders make keeping the camera at optimal levels relatively easy under normal circumstances. This section will focus on the major operational items and controls of studio cameras: (1) power supply, (2) camera cable, (3) connectors, (4) filter wheel, (5) viewfinder, (6) tally light, (7) intercom. 11
Operational Characteristics (2/5) Power supply All studio cameras receive power from a DC (direct current) power supply which is supplied through the camera cable. Camera cables differ in how they carry the various electronic signals to and from the camera. The 3 (three) characteristics of camera cables: ü Multi-core cables: contain a great number of thin wires with the most limited reach (up to 2, 000 feet or about 600 meters), can carry a great amount of information without any adapters; ü The triaxial (triax) cables: have one central wire surrounded by two concentric shields, can reach maximum of 5, 000 feet (1, 500 meters); ü The fiber-optic cables: contain thin, flexible, glass strands instead of wires, can reach 2 miles (up to 3, 000 meters) both triax and fiber-optic are thinner and considerably lighter than multi-core and need adapters. 12
Operational Characteristics (3/5) Connectors When using studio cameras in the field, please carefully check if the cable connectors fit the jacks of the remote truck. Simple coaxial video lines all have BNC connectors and multi-core cables come in various configurations which are usually expressed in the number of pins at the cable end. Filter wheel It is located between the lens and beam splitter. It normally holds two neutral density filters (NDS), referred to as ND-1 and ND 2 and some color-correction filters. The NDs reduce the amount of light transmitted to the imaging device without affecting the color of the scene and these are used when shooting in bright sunlight. As for color-correction filters, they compensate for the relative bluishness of outdoor and fluorescent light and relative reddishness of 13 indoor and candlelight.
Operational Characteristics (4/5) Viewfinder is a small television set that shows the picture the camera is getting. The characteristics of viewfinders are as follows: ü In studio cameras, they are usually in 5 - or 7 - inch and can be swiveled and tilted; ü Mostly monochrome (even in HDTV cameras) that means only can see black and white picture of the scene; ü Also act as a small information center that indicates the following items and conditions: a. center maker: that shows the exact center of the screen; b. safe title area: a rectangle in the viewfinder within which all essential picture information should be kept; c. Electronic set up: that includes a variety of control functions such as electronic gain, optimal video levels, electronic shutter. d. Lens extenders: the magnifying devices that extend the telephoto power of a lens; 14 e. Multiple views: this allows to see pictures and the special effects.
Operational Characteristics (5/5) Tally light A big red light on top of studio camera that signals which of the two or more cameras is on the air. This tally light may function: § to assist the talent to indicate the correct camera; § to inform the camera operator when the camera is on; § to acknowledge that two cameras are used simultaneously for a splitscreen effect or for a superimposition; § when off, tally light may help the camera operator to position the studio camera. Intercommunication is significant for multi-camera production for the director and technical director to be able to coordinate. There usually at least two channels for intercom: (1) for the production crew, (2) for the 15 technical crew.
Operational Items (1/3) Operational Items: ENG/ EFP Cameras and Camcorders The following explanations are descriptions of the operational items the functions of field cameras. Power supply ü Most professional camcorders are powered by 13 - or 14 volt battery; ü Consumer camcorders have lower-voltage batteries; ü Substitute power supplies are AC current and car batteries; ü Most batteries can supply continuous power for up to two hours before recharging; ü When operating professional camcorders use digital battery; ü To avoid the risk of having a camera stop working right in the middle of a shoot, always charge the battery well before the period indicated by 16 the manufacturer’s charge rating is up.
Operational Items (2/3) Camera cable is used to connect the camera to videotape recorder or remote control, or to some other external equipments like monitor feeds, audio recorders, etc. Connectors used to connect camera with receptacle: BNC connectors for video coaxial cables, XLR or RCA phono plugs for audio cables, consumer equipment usually uses RCA phono for video cables and mini plugs for audio. Exchangeable lenses Most professional ENG/ EFP cameras use zoom lens that allow to have optimal zoom range. 17
Operational Items (3/3) Filter wheel contains at least 2 (two) NDs and a variety of colorcorrection filters. Viewfinder Most studio and field camera viewfinders will include the indicators like: (1) tally light, (2) VTR record, (3) End-of tape warning, (4) the white balance, (5) battery status, (6) maximum and minimum light levels, (7) gain, (8) optical filter positions, (9) playback. Operational Controls: ENG/ EFP Cameras and Camcorders Since Eng/ EFP cameras represent not only camera head but also the entire of camera chain (CCU, power supply, and sync generator), then the cameras have switches and knobs more sophisticated than the studio cameras: (1) power switch, (2) standby switch, (3) the gain control, (4) white balance, (5) filter wheel, (6) the VTR, (7) the shutter speed, (8) the camera/ bars selection, (9) the audio level, (10) sound volume and audio monitor 18 control, (11) VTR controls.