A webcam is a "video camera that feeds or "streams its image in real time to or through a "computer to a "computer network. When "captured" by the computer, the video stream may be saved, viewed or sent on to other networks via systems such as the internet, and emailed as an attachment. When sent to a remote location, the video stream may be saved, viewed or on sent there. Unlike an "IP camera (which connects using "Ethernet or "Wi-Fi), a webcam is generally connected by a "USB cable, or similar cable, or built into computer hardware, such as laptops.
The term "webcam" (a "clipped compound) may also be used in its original sense of a "video camera connected to the "Web continuously for an indefinite time, rather than for a particular session, generally supplying a view for anyone who visits its "web page over the Internet. Some of them, for example, those used as online "traffic cameras, are expensive, rugged "professional video cameras.
Webcams are known for their low "manufacturing cost and their high flexibility, making them the lowest-cost form of "videotelephony. Despite the low cost, the "resolution offered at present (2015) is rather impressive, with low-end webcams offering resolutions of 320×240, medium webcams offering 640×480 resolution, and high-end webcams offering 1280×720 (aka "720p) or even 1920×1080 (aka "1080p) resolution.
They have also become a source of security and privacy issues, as some built-in webcams can be remotely activated by "spyware.
The most popular use of webcams is the establishment of "video links, permitting computers to act as "videophones or "videoconference stations. Other popular uses include security surveillance, "computer vision, video broadcasting, and for recording social videos.
The video streams provided by webcams can be used for a number of purposes, each using appropriate software:
Most modern webcams are capable of capturing arterial pulse rate by the use of a simple algorithmic trick. Researchers claim that this method is accurate to ±5 bpm.
Webcams may be installed at places such as childcare centres, offices, shops and private areas to monitor security and general activity.
Webcams have been used for "augmented reality experiences online. One such function has the webcam act as a "magic mirror" to allow an online shopper to view a virtual item on themselves. The "Webcam Social Shopper is one example of software that utilizes the webcam in this manner.
Webcam can be added to "instant messaging, text chat services such as "AOL Instant Messenger, and "VoIP services such as "Skype, one-to-one live video communication over the Internet has now reached millions of mainstream "PC users worldwide. Improved video quality has helped webcams encroach on traditional video conferencing systems. New features such as automatic lighting controls, real-time enhancements (retouching, wrinkle smoothing and vertical stretch), automatic "face tracking and autofocus, assist users by providing substantial ease-of-use, further increasing the popularity of webcams.
Webcam features and performance can vary by "program, "computer operating system, and also by the computer's "processor capabilities. Video calling support has also been added to several "popular instant messaging programs.
Webcams can be used as "security cameras. Software is available to allow PC-connected cameras to watch for movement and sound, recording both when they are detected. These recordings can then be saved to the computer, e-mailed, or uploaded to the Internet. In one well-publicised case, a computer e-mailed images of the burglar during the theft of the computer, enabling the owner to give police a clear picture of the burglar's face even after the computer had been stolen.
Unauthorized access of webcams can present significant privacy issues (see "Privacy" section below).
Webcams can be used to take "video clips and "still pictures. Various software tools in wide use can be employed for this, such as "PicMaster (for use with "Windows operating systems), "Photo Booth ("Mac), or "Cheese (with "Unix systems). For a more complete list see "Comparison of webcam software.
Special software can use the video stream from a webcam to assist or enhance a user's control of applications and games. Video features, including faces, shapes, models and colors can be observed and tracked to produce a corresponding form of control. For example, the position of a single light source can be tracked and used to emulate a mouse pointer, a head-mounted light would enable "hands-free computing and would greatly improve "computer accessibility. This can be applied to games, providing additional control, improved interactivity and immersiveness.
"FreeTrack is a free webcam motion-tracking application for "Microsoft Windows that can track a special head-mounted model in up to six "degrees of freedom and output data to mouse, keyboard, joystick and "FreeTrack-supported games. By removing the IR filter of the webcam, IR LEDs can be used, which has the advantage of being invisible to the naked eye, removing a distraction from the user. "TrackIR is a commercial version of this technology.
The "EyeToy for the "PlayStation 2, "PlayStation Eye for the "PlayStation 3, and the "Xbox Live Vision camera and "Kinect motion sensor for the "Xbox 360 and are color digital cameras that have been used as control input devices by some games.
With very-low-light capability, a few specific models of webcams are very popular to photograph the night sky by astronomers and astro photographers. Mostly, these are manual-focus cameras and contain an old CCD array instead of comparatively newer CMOS array. The lenses of the cameras are removed and then these are attached to telescopes to record images, video, still, or both. In newer techniques, videos of very faint objects are taken for a couple of seconds and then all the frames of the video are "stacked" together to obtain a still image of respectable contrast.
A webcam's CCD response is linear proportional to the incoming light.  Therefore, webcams are suitable to record laser beam profiles, after the lens is removed. The resolution of a "laser beam profiler depends on the pixel size. Commercial webcams are usually designed to record color images. The size of a webcam's color pixel depends on the model and may lie in the range of 5 to 10µm. However, a color pixel consists of four black and white pixels each equipped with a color filter (for details see "Bayer filter). Although these color filters work well in the visible, they may be rather transparent in the near infra-red. By switching a webcam into the Bayer-mode it is possible to access the information of the single pixels and a resolution below 3µm was possible. 
First developed in 1991, a webcam was pointed at the "Trojan Room coffee pot in the "Cambridge University Computer Science Department (initially operating over a local network instead of the web). The camera was finally switched off on August 22, 2001. The final image captured by the camera can still be viewed at its homepage. In 2004, the oldest webcam still operating was FogCam at "San Francisco State University, which had been running continuously since 1994.
The first commercial webcam, the black-and-white "QuickCam, entered the marketplace in 1994, created by the U.S. computer company "Connectix (which sold its product line to "Logitech in 1998). QuickCam was available in August 1994 for the "Apple Macintosh, connecting via a "serial port, at a cost of $100. Jon Garber, the designer of the device, had wanted to call it the "Mac-camera", but was overruled by Connectix's marketing department; a version with a PC-compatible serial port and software for "Microsoft Windows was launched in October 1995. The original QuickCam provided 320x240-pixel resolution with a grayscale depth of 16 shades at 60 frames per second, or 256 shades at 15 frames per second. These cam were tested on several Delta II launch using a variety of communication protocols including CDMA, TDMA, GSM and HF.
One of the most widely reported-on webcam sites was "JenniCam, created in 1996, which allowed Internet users to observe the life of its namesake constantly, in the same vein as the "reality TV series "Big Brother, launched four years later. Other cameras are mounted overlooking bridges, public squares, and other public places, their output made available on a public web page in accordance with the original concept of a "webcam". Aggregator websites have also been created, providing thousands of live video streams or up-to-date still pictures, allowing users to find live video streams based on location or other criteria.
Around the turn of the 21st century, computer hardware manufacturers began building webcams directly into "laptop and desktop screens, thus eliminating the need to use an external USB or "FireWire camera. Gradually webcams came to be used more for telecommunications, or "videotelephony, between two people, or among several people, than for offering a view on a Web page to an unknown public.
For less than US$100 in 2012, a "three-dimensional space webcam became available, producing videos and photos in 3D "anaglyph image with a resolution up to 1280 × 480 pixels. Both sender and receiver of the images must use 3D glasses to see the effect of three dimensional image.
Webcams typically include a lens, an "image sensor, support electronics, and may also include a "microphone for sound. Various lenses are available, the most common in consumer-grade webcams being a plastic "lens that can be screwed in and out to focus the camera. "Fixed-focus lenses, which have no provision for adjustment, are also available. As a camera system's "depth of field is greater for small image formats and is greater for lenses with a large "f-number (small aperture), the systems used in webcams have a sufficiently large depth of field that the use of a fixed-focus lens does not impact image sharpness to a great extent.
Image sensors can be "CMOS or "CCD, the former being dominant for low-cost cameras, but CCD cameras do not necessarily outperform CMOS-based cameras in the low-price range. Most consumer webcams are capable of providing "VGA-resolution video at a "frame rate of 30 frames per second. Many newer devices can produce video in multi-"megapixel resolutions, and a few can run at high frame rates such as the "PlayStation Eye, which can produce "320×240 video at 120 frames per second.
Support electronics read the image from the sensor and transmit it to the host computer. The camera pictured to the right, for example, uses a Sonix SN9C101 to transmit its image over "USB. Typically, each frame is transmitted uncompressed in "RGB or "YUV or compressed as "JPEG. Some cameras, such as "mobile-phone cameras, use a CMOS sensor with supporting electronics "on die", i.e. the sensor and the support electronics are built on a single "silicon chip to save space and manufacturing costs. Most webcams feature built-in "microphones to make "video calling and "videoconferencing more convenient.
The "USB video device class (UVC) specification allows interconnectivity of webcams to computers without the need for proprietary device drivers. Microsoft "Windows XP SP2, "Linux and "Mac OS X (since October 2005) have UVC support built in and do not require extra device drivers, although they are often installed to add additional features.
Many users do not wish the continuous exposure for which webcams were originally intended, but rather prefer privacy. Such privacy is lost when "malware allow "malicious hackers to activate the webcam without the user's knowledge, providing the hackers with a live video and audio feed. This is a particular concern on many laptop computers, as such cameras normally cannot be physically disabled if hijacked by such a "Trojan Horse program or other similar "spyware programs.
Cameras such as "Apple's older external "iSight cameras include lens covers to thwart this. Some webcams have built-in hardwired "LED indicators that light up whenever the camera is active, sometimes only in video mode["citation needed]. However, it is possible for "malware to circumvent the indicator and activate the camera surrepticiously, as researchers demonstrated in case of a "MacBook's built-in camera in 2013.
Various companies sell sliding lens covers and stickers that allow users to retrofit a computer or smartphone to close access to the camera lens as needed. One such company reported having sold more than 250,000 such items from 2013 to 2016. Prominent users include FBI director "James Comey.
The fraudulent process of attempting to hack into a person's webcam and activate it without the webcam owner's permission has been called "camfecting. The remotely activated webcam can be used to watch anything within the webcam's field of vision, sometimes the webcam owner itself. Camfecting is most often carried out by infecting the victim's computer with a virus that can provide the hacker access to the victim's webcam. This attack is specifically targeted at the victim's webcam, and hence the name camfecting, a "portmanteau of the words cam and infecting.
In January 2005, some "search engine queries were published in an online forum which allow anyone to find thousands of "Panasonic- and "Axis high-end web cameras, provided that they have a web-based "interface for remote viewing. Many such cameras are running on default configuration, which does not require any "password login or "IP address verification, making them viewable by anyone.
In the 2010 "Robbins v. Lower Merion School District "WebcamGate" case, plaintiffs charged that two suburban Philadelphia high schools secretly spied on students - by surreptitiously remotely activating iSight webcams embedded in school-issued "MacBook laptops the students were using at home — and thereby infringed on their privacy rights. School authorities admitted to secretly snapping over 66,000 photographs, including shots of students in the privacy of their bedrooms, including some with teenagers in various state of undress. The school board involved quickly disabled their laptop spyware program after parents filed lawsuits against the board and various individuals.
Webcams allow for inexpensive, real-time "video chat and "webcasting, in both amateur and professional pursuits. They are frequently used in "online dating and for online personal services offered mainly by women when "camgirling. However, the ease of webcam use through the Internet for video chat has also caused issues. For example, moderation system of various video chat websites such as "Omegle has been criticized as being ineffective, with sexual content still rampant. In a 2013 case, the transmission of nude photos and videos via Omegle from a teenage girl to a schoolteacher resulted in a "child pornography charge.
"YouTube is a popular website hosting many videos made using webcams. News websites such as the "BBC also produce professional live news videos using webcams rather than traditional cameras.["better source needed]
Webcams can also encourage "telecommuting, enabling people to work from home via the Internet, rather than traveling to their office.
The popularity of webcams among teenagers with Internet access has raised concern about the use of webcams for "cyber-bullying. Webcam recordings of teenagers, including underage teenagers, are frequently posted on popular Web forums and "imageboards such as "4chan.
Videophone calls (also: videocalls and "video chat), differ from "videoconferencing in that they expect to serve individuals, not groups. However that distinction has become increasingly blurred with technology improvements such as "increased bandwidth and sophisticated "software clients that can allow for multiple parties on a call. In general everyday usage the term videoconferencing is now frequently used instead of videocall for point-to-point calls between two units. Both videophone calls and videoconferencing are also now commonly referred to as a video link.
Webcams are popular, relatively low cost devices which can provide live video and audio streams via personal computers, and can be used with many "software clients for both video calls and videoconferencing.
A "videoconference system is generally higher cost than a videophone and deploys greater capabilities. A videoconference (also known as a videoteleconference) allows two or more locations to communicate via live, simultaneous two-way video and audio transmissions. This is often accomplished by the use of a "multipoint control unit (a centralized distribution and call management system) or by a similar non-centralized multipoint capability embedded in each videoconferencing unit. Again, technology improvements have circumvented traditional definitions by allowing multiple party videoconferencing via web-based applications. A separate webpage article is devoted to "videoconferencing.
A "telepresence system is a high-end videoconferencing system and service usually employed by "enterprise-level corporate offices. Telepresence conference rooms use state-of-the art room designs, video cameras, displays, sound-systems and processors, coupled with high-to-very-high capacity bandwidth transmissions.
Typical use of the various technologies described above include calling or conferencing on a one-on-one, one-to-many or many-to-many basis for personal, business, educational, "deaf Video Relay Service and "tele-medical, diagnostic and "rehabilitative use or services. New services utilizing videocalling and videoconferencing, such as teachers and psychologists conducting online sessions, personal videocalls to "inmates incarcerated in penitentiaries, and videoconferencing to resolve "airline engineering issues at "maintenance facilities, are being created or evolving on an ongoing basis.
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