Camcorder videocamera recorder



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Video: Analog Video Camera

A camcorder (videocamera recorder) is an electronic device that combines a video camera and a video recorder into one unit.[1][2][3] Equipment manufacturers do not seem to have strict guidelines for the term usage. Marketing materials may present a video recording device as a camcorder, but the delivery package would identify content as video camera recorder.

In order to differentiate a camcorder from other devices that are capable of recording video, like mobile phones and digital compact cameras, a camcorder is generally identified as a portable, self-contained device having video capture and recording as its primary function.[4][5]

The earliest camcorders employed analog recording onto videotape. Tape-based camcorders use removable media in the form of video cassettes. Nowadays, digital recording has become the norm, with tape being gradually replaced with other storage media such as internal flash memory, hard drive, and SD card. As of January 2011, none of the new consumer-class camcorders announced at the 2011 International Consumer Electronics Show record on tape.[6]

Camcorders that do not use magnetic tape are often called tapeless camcorders, while camcorders that permit using more than one type of medium, like built-in hard disk drive and memory card, are sometimes called hybrid camcorders.

Overview

Camcorders contain 3 major components: lens, imager, and recorder. The lens gathers and focuses light on the imager. The imager (usually a CCD or CMOS sensor on modern camcorders; earlier examples often used vidicon tubes) converts incident light into an electrical signal. Finally, the recorder converts the electric signal into video and encodes it into a storable form. More commonly, the optics and imager are referred to as the camera section.



[edit] Lens

The lens is the first component in the light path. The camcorder's optics generally have one or more of the following adjustments:



  • aperture or iris to regulate the exposure and to control depth of field;

  • zoom to control the focal length and angle of view;

  • shutter speed to regulate the exposure and to maintain desired motion portrayal;

  • gain to amplify signal strength in low-light conditions;

  • neutral density filter to regulate the exposure.

In consumer units, the above adjustments are often automatically controlled by the camcorder's electronics, but can be adjusted manually if desired. Professional units offer direct user control of all major optical functions.

[edit] Imager

The imager converts light into electric signal. The camera lens projects an image onto the imager surface, exposing the photosensitive array to light. The light exposure is converted into electrical charge. At the end of the timed exposure, the imager converts the accumulated charge into a continuous analog voltage at the imager's output terminals. After scan-out is complete, the photosites are reset to start the exposure-process for the next video frame.



[edit] Recorder

The recorder is responsible for writing the video-signal onto a recording medium (such as magnetic videotape.) The record function involves many signal-processing steps, and historically, the recording-process introduced some distortion and noise into the stored video, such that playback of the stored-signal may not retain the same characteristics/detail as the live video feed.

All but the most primitive camcorders imaginable also need to have a recorder-controlling section which allows the user to control the camcorder, switch the recorder into playback mode for reviewing the recorded footage and an image control section which controls exposure, focus and white-balance.

The image recorded need not be limited to what appeared in the viewfinder. For documentation of events, such as used by police, the field of view overlays such things as the time and date of the recording along the top and bottom of the image. Such things as the police car or constable to which the recorder has been allotted may also appear; also the speed of the car at the time of recording. Compass direction at time of recording and geographical coordinates may also be possible. These are not kept to world-standard fields; "month/day/year" may be seen, as well as "day/month/year", besides the ISO standard "year-month-day".



[edit] Consumer camcorders

[edit] Analog vs. digital

Camcorders are often classified by their storage device: VHS, VHS-C, Betamax, Video8 are examples of 20th century videotape-based camcorders which record video in analog form. Newer digital video camcorder formats include Digital8, MiniDV, DVD, Hard disk drive direct to disk recording and solid-state semiconductor Flash memory memory. While all these formats record video in digital form, currently formats like Digital8, MiniDV and DVD have been losing favor, and are no longer used in the most recent consumer camcorders.

In older analog camcorders, the imaging device was based on vacuum tube technology where the charge on a light sensitive target was in direct proportion to the amount of light striking it. A popular example of such an imaging tube was the Vidicon. Newer analog and all digital camcorders use a solid state Charge Coupled Device (CCD) imaging device, or more recently a CMOS imager. Both of these latter devices use photodiodes that pass a current proportional to the light striking them (i.e. they are analog detectors), but that current is then digitised before being electronically 'scanned' before being fed to the imager's output. The principal difference in the latter two devices is in the manner in which that 'scanning' is accomplished. In the CCD, the diodes are all sampled simultaneously, and the scanning then achieved by passing the digitised data from one register to the next (the Charge Coupled element). In the CMOS device the diodes are sampled directly by the scanning logic.

The take up of digital video storage improved quality. MiniDV storage allows full resolution video (720x576 for PAL, 720x480 for NTSC), unlike previous analogue consumer video standards. Digital video does not experience colour bleeding, jitter, or fade, although some users still prefer the analog nature of Hi8 and Super VHS-C, since neither of these produce the "background blur" or "mosquito noise" of digital video compression. In many cases, a high-quality analog recording shows more detail (such as rough textures on a wall) than a compressed digital recording (which would show the same wall as flat and featureless).

Unlike analog video formats, the digital video formats do not suffer generation loss during dubbing, but can be more prone to complete loss. Theoretically digital information can be stored indefinitely with zero deterioration on a digital storage device (such as a hard drive), however since some digital formats (like MiniDV) often squeeze tracks only ~10 micrometers apart (versus 19 to 58 μm for VHS), a digital recording is more vulnerable to wrinkles or stretches in the tape that could permanently erase several scenes worth of digital data, but the additions tracking and error correction code on the tape will generally compensate for most defects. On analog media similar damage barely registers as "noise" in the video, still leaving a deteriorated but watchable video. The only limitation is that this video has to be played on a completely analogue viewing system, otherwise the tape will not display any video due to the damage and sync problems. Even digital recordings on DVD are known to suffer from DVD rot that permanently erase huge chunks of data. Thus the one advantage analog seems to have in this respect is that an analog recording may be "usable" even after the media it is stored on has suffered severe deterioration whereas it has been noticed[9] that even slight media degradation in digital recordings may cause them to suffer from an "all or nothing" failure, i.e. the digital recording will end up being totally un-playable without very expensive restoration work.

[edit] Modern recording media

For more information, see tapeless camcorder.

While some older digital camcorders record video on Microdrives and size-reduced DVD-RAM or DVD-Rs, as of 2011 most recent camcorders record video on flash memory devices and small hard disks, using MPEG-1, MPEG-2 or MPEG-4 formats. However, because these codecs use inter-frame compression, frame-specific-editing requires frame regeneration, which incurs additional processing and can cause loss of picture information. (In professional usage, it is common to use a codec that will store every frame individually. This provides easier and faster frame-specific editing of scenes.)

Other digital consumer camcorders record in DV or HDV format on tape and transfer content over FireWire (some also use USB 2.0) to a computer, where the huge files (for DV, 1GB for 4 to 4.6 minutes in PAL/NTSC resolutions) can be edited, converted, and (with many camcorders) also recorded back to tape. The transfer is done in real time, so the complete transfer of a 60 minute tape needs one hour to transfer and about 13GB disk space for the raw footage only—excluding any space needed for render files, and other media. Time spent in post-production (editing) to select and cut the best shots varies from instantaneous "magic" movies to hours of tedious selection, arrangement and rendering.

[edit] Consumer market

As the mass consumer market favors ease of use, portability, and price, most of the consumer-grade camcorders sold today emphasize handling and automation features over raw audio/video performance. Thus, the majority of devices capable of functioning as camcorders are camera phones or compact digital cameras, for which video is only a feature or a secondary capability.

Even for separate devices intended primarily for motion video, this segment has followed an evolutionary path driven by relentless miniaturization and cost reduction, made possible by progress in design and manufacturing. Miniaturization conflicts with the imager's ability to gather light, and designers have delicately balanced improvements in sensor sensitivity with sensor size reduction, shrinking the overall camera imager & optics, while maintaining reasonably noise-free video in broad daylight. Indoor or dim light shooting is generally unacceptably noisy, and in such conditions, artificial lighting is highly recommended. Mechanical controls cannot scale below a certain size, and manual camera operation has given way to camera-controlled automation for every shooting parameter (focus, aperture, shutter speed, white balance, etc.) The few models that do retain manual override frequently require the user to navigate a cumbersome menu interface. Outputs include USB 2.0, Composite and S-Video, and IEEE 1394/Firewire (for MiniDV models). On the plus side, today's camcorders are affordable to a wider segment of the consumer market, and available in a wider variety of form factors and functionality, from the classic camcorder shape, to small flip-cameras, to video-capable camera-phones and "digicams."

At the high-end of the consumer market, there is a greater emphasis on user control and advanced shooting modes. Feature-wise, there is some overlap between the high-end consumer and "prosumer" markets. More expensive consumer camcorders generally offer manual exposure control, HDMI output and external audio input, progressive-scan framerates (24fps, 25fps, 30fps), and better lenses than basic models. In order to maximize low-light capability, color reproduction, and frame resolution, a few manufacturers offer multi-CCD/CMOS camcorders, which mimic the 3-element imager design used in professional equipment. Field tests have demonstrated most consumer camcorders (regardless of price), to produce noisy video in low light.

Before the 21st century, video editing was a difficult task requiring a minimum of two recorders and possibly a desktop video workstation to control them. Now, the typical home personal computer can hold several hours of standard-definition video, and is fast enough to edit footage without additional upgrades. Most consumer camcorders are sold with basic video editing software, so users can easily create their own DVDs, or share their edited footage online.

http://upload.wikimedia.org/wikipedia/en/thumb/9/94/jvc_gz-mg555-02.jpg/220px-jvc_gz-mg555-02.jpg

JVC GZ-MG555 hybrid camcorder (MPEG-2 SD Video)

In the first world market, nearly all camcorders sold today are digital. Tape-based (MiniDV/HDV) camcorders are no longer popular, since tapeless models (SD card & internal drive) cost almost the same, but offer much greater convenience. For example, video captured on SD card can be transferred to a computer much faster than from digital tape. Hard disk camcorders feature the longest continuous recording time, though the durability of the hard drive is a concern for harsh and high-altitude environments. As of January 2011, none of the new consumer-class camcorders announced at the 2011 International Consumer Electronics Show record on tape.[6] However, in some parts of the world, newly-manufactured tape camcorders might still be available due to the lower purchasing power or greater price sensitivity of the consumers in these areas.

[edit] Other devices with video-capture capability

Video-capture capability is not confined to camcorders. Cellphones, digital single lens reflex and compact digicams, laptops, and personal media players frequently offer some form of video-capture capability. In general, these multipurpose-devices offer less functionality for video-capture, than a traditional camcorder. The absence of manual adjustments, external-audio input, and even basic usability functions (such as autofocus and lens-zoom) are common limitations. Few can capture to standard TV-video formats (480p60, 720p60, 1080i30), and instead record in either non-TV resolutions (320x240, 640x480, etc.) or slower frame-rates (15fps, 30fps.)

When used in the role of a camcorder, a multipurpose-device tends to offer inferior handling and audio/video performance, which limits its usability for extended and/or adverse shooting situations. However, much as camera-equipped cellphones are now ubiquitous, video-equipped electronic devices will likely become commonplace, replacing the market for low-end camcorders.

The past few years have seen the introduction of DSLR cameras with high-definition video. Although they still suffer from the typical handling and usability deficiencies of other multipurpose-devices, HDSLR video offers two videographic features unavailable on consumer camcorders: shallow depth-of-field and interchangeable lenses. Professional video cameras possessing these capabilities are currently more expensive than even the most expensive video-capable DSLR. In video applications where the DSLR's operational deficiencies can be mitigated by meticulous planning of the each shooting location, a growing number of video productions are employing DSLRs, such as the Canon 5D Mark II, to fulfill the desire for depth-of-field and optical-perspective control. Whether in a studio or on-location setup, the scene's environmental factors and camera placement are known beforehand, allowing the director of photography to determine the proper camera/lens setup and apply any necessary environmental adjustments, such as lighting.

A recent development to combine the feature-sets of full-feature still-camera and camcorder in a single unit, is the combo-camera. The Sanyo Xacti HD1 was the first such combo unit, combining the features of a 5.1 megapixel still-camera with a 720p video recorder. Overall, the product was a step forward in terms of a single-device's combined level of handling and usability . The combo camera's concept has caught on with competing manufacturers; Canon and Sony have introduced camcorders with still-photo performance approaching a traditional digicam, while Panasonic has introduced a DSLR-body with video features approaching a traditional camcorder. Hitachi have introduced the DZHV 584E/EW which has 1080p resolution. This model comes with a 3" pop-up touch screen, housed in a slim line-case and about the size of a mobile phone.

[edit] Interchangeable lens camcorder

As reverse of DSLR cameras with high-definition video, in 2011 at least there are 2 Interchangeable lens camcorders which can capture Full HD video with full control of camcorder, Panasonic AG-AF100 and Sony NEX-VG10 both with big sensor, not as usual as non-professional camcorders. The DSLR lenses can be used with adapter for versatilities.[10]



[edit] Camcorder with built-in projector

In 2011 Sony released the HDR-PJ10/30/50 HD camcorders. These are the first camcorders in the world to incorporate a small projector located on the side of the unit. This feature allows the user to show their video to a group of viewers without the need to connect up to a television or a full-size projector or even to upload onto a computer. Such a feature would have been unimaginable only a generation ago. The specification varies between each model, the HDR-PJ10 is the base model with 16GB internal memory. The HDR-PJ30 has double the capacity (32GB), an additional light to aid in darkness and the ability to shoot a 25p image making the video appear as if it was shot on film. The HDR-PJ50 is the top of the range model with a 220GB hard disk drive as well as the light to aid in darkness. While the projector could be seen as useful feature, it's unknown whether any other manufacturer would include such a feature on a camcorder in the future, only time will tell.[11]



File:Sony HDR-PJ10.jpg

Sony HDR-PJ10 camcorder with built in projector



[edit] 3D Camcorder

In 2011 Panasonic released the world's first camcorder to be capable of shooting in 3D, the HDC-SDT750. It is a regular 2D camcorder that can shoot in full HD while 3D is achieved by the detachable conversion lens. Sony subsequently released its own 3D camcorder, the HDR-TD10. Unlike the Panasonic, the Sony HDR-TD10 has the 3D lens built in but it can still shoot a normal 2D video. The down side to this is that it results in a rather ugly design and a high price tag (£1,005.70 for the Sony vs. £686 for the Panasonic on Amazon). Panasonic have also released normal 2D camcorders with optional 3D recording with the conversion lens being an optional extra. The HDC-SD90, HDC-SD900, HDC-TM900 and HDC-HS900 are marketed as '3D ready' being affordable regular 2D camcorders with the option to add the 3D capability at a later date. Sony and some other manufacturers have even marketed 3D pocket camcorders, an example being the Sony MHS-FS3. Sony are releasing the DEV-5 3D camcorder, however Sony markets it as digital recording binoculars due to the shape of the unit. The down side of this unusual camcorder is the hefty price tag, £2,605 on Sony's website, almost treble that of the Sony HDR-TD10. Currently only Panasonic and Sony manufacture 3D camcorders but it is unknown is to whether these will catch on, only time will tell.



[edit] Uses

[edit] Media

http://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/camcorder_in_use_-_sa.jpg/220px-camcorder_in_use_-_sa.jpg

Operating a camcorder

Camcorders have found use in nearly all corners of electronic media, from electronic news organizations to TV/current-affairs productions. In locations away from a distribution infrastructure, camcorders are invaluable for initial video acquisition. Subsequently, the video is transmitted electronically to a studio/production center for broadcast. Scheduled events such as official press conferences, where a video infrastructure is readily available or can be feasibly deployed in advance, are still covered by studio-type video cameras (tethered to "production trucks.")

[edit] Home video

For casual use, camcorders often cover weddings, birthdays, graduation ceremonies, children growing up, and other personal events. The rise of the consumer camcorder in the mid to late '80s led to the creation of shows such as the long-running America's Funniest Home Videos, where people could showcase homemade video footage.



[edit] Politics

Political protestors who have capitalized on the value of media coverage use camcorders to film things they believe to be unjust. Animal rights protesters who break into factory farms and animal testing labs use camcorders to film the conditions the animals are living in. Anti-hunting protesters film fox hunts. People expecting to witness political crimes use cameras for surveillance to collect evidence. Activist videos often appear on Indymedia.

The police use camcorders to film riots, protests and the crowds at sporting events. The film can be used to spot and pick out troublemakers, who can then be prosecuted in court. In countries such as the United States, the use of compact dashboard camcorders in police cars allows the police to retain a record of any activity that takes place in front of the car, such as interaction with a motorist stopped on the highway.

[edit] Entertainment and movies

Camcorders are often used in the production of low-budget TV shows where the production crew does not have access to more expensive equipment. There are even examples of movies shot entirely on consumer camcorder equipment (such as The Blair Witch Project and 28 Days Later). In addition, many academic filmmaking programs have switched from 16mm film to digital video, due to the vastly reduced expense and ease of editing of the digital medium as well as the increasing scarcity of film stock and equipment. Some camcorder manufacturers cater to this market, particularly Canon and Panasonic, who both support "24p" (24 frame/s, progressive scan; same frame rate as standard cinema film) video in some of their high-end models for easy film conversion.

Even high-budget cinema is done using camcorders in some cases; George Lucas used Sony CineAlta camcorders in two of his three Star Wars prequel movies. This process is referred to as digital cinematography.

[edit] Education, Teacher Evaluation and Teacher Preparation

Secondary Education and Higher Education in the developed world is increasingly integrating digital media and computing into the fabric of students learning experiences. Students often use camcorders to record video diaries, make short films, and develop a variety of multi-media projects across subject disciplines.

Meanwhile teacher evaluation increasingly involves teacher's classroom lessons being digitally recorded for review by school administrators and school district officials. This is especially common during the process of tenure-granting (or withholding), and in cases where teacher's continued tenure may be in question. Some feel the use of digital recording allows both school districts and teacher's unions an opportunity to more objectively and comprehensively review aspects of teacher performance in the classroom setting, whilst others, such as Alfie Kohn are far more skeptical.

Recently in many a top ranked School of Education, integration of student camcorder-created material as well as other digital technology has ingrained itself into the fabric of new teacher preparation courses. The University of Oxford Department of Education PGCE programme and NYU's Steinhardt School's Department of Teaching and Learning MAT programme provide two examples of this trend.

The USC Rossier School of Education takes this one step further, by insisting that all students purchase their own camcorder (or similar digital video recording devise) as a prerequisite to beginning their MAT education programmes, many of which are delivered entirely online. These programmes employ a modified version of Adobe Connect to deliver the entire taught component of the MAT@USC. MAT students in-class teaching is captured by camcorder, posted to USC's web portal, and then go through a process of evaluation by faculty in a similar manner to what they would use if they were physically present in class.

In this way the use of the camcorder has allowed USC to entirely de-centralize its teacher preparation away from Southern California to most American states, and several countries around the world; and this has greatly increased the number of teachers they are able to train at once. With significant teacher shortages looming in the USA, UK, Canada and Australia over the next few years, this is likely to be a model which other institutions seek to emulate

Transmission of Video Signals




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