Digital camera

Digital camera


A digital camera (or digicam for short) is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor.
Front and back of a Canon PowerShot A95.

Many compact digital still cameras can record sound and moving video as well as still photographs. In the Western market, digital cameras outsell their 35 mm film counterparts.[1]

Digital cameras can do things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, recording video with sound, and deleting images to free storage space. Some can crop pictures and perform other elementary image editing. Fundamentally they operate in the same manner as film cameras, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The combination of the diaphragm and a shutter mechanism is used to admit the correct amount of light to the imager, just as with film; the only difference is that the image pickup device is electronic rather than chemical.

Digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles. The Hubble Space Telescope and other astronomical devices are essentially specialised digital camera



Compact digital cameras

Compact cameras are designed to be small and portable and are particularly suitable for casual and "snapshot" use, thus are also called point-and-shoot camera. The smallest, generally less than 20 mm thick, are described as subcompacts or "ultra-compacts". Compact cameras are usually designed to be easy to use, sacrificing advanced features and picture quality for compactness and simplicity; images can usually only be stored using lossy compression (JPEG). Most have a built-in flash usually of low power, sufficient for nearby subjects. Live preview is almost always used to frame the photo. They may have limited motion picture capability. Compacts often have macro capability, but if they have zoom capability the range is usually less than for bridge and DSLR cameras. Generally a contrast-detect autofocus system, using the image data from the live preview feed off the main imager, focuses the lens.

Typically, these cameras incorporate a nearly-silent leaf shutter into their lenses.

To enable lower costs and smaller size, these cameras typically use image sensors with a diagonal of approximately 6 mm, corresponding to a crop factor around 6. This gives them weaker low-light performance, greater depth of field, generally closer focusing ability, and smaller components than cameras using larger sensors.

[edit] Bridge cameras
Main article: Bridge digital camera

Bridge or SLR-like cameras are higher-end digital cameras that physically and ergonomically resemble DSLRs and share with them some advanced features, but share with compacts the use of a fixed lens and a small sensor. Like compacts, most use live preview to frame the image. Autofocus is achieved using the same contrast-detect mechanism, but many bridge cameras feature a manual focus mode for greater control.
Fujifilm FinePix S9000.

Due to the combination of large physical size but a small sensor, many of these cameras have very highly specified lenses with large zoom ranges and fast apertures, partially compensating for the inability to change lenses. A typical example is the lens on the Panasonic FZ50, a 35-420mm equivalent lens with an aperture of 1:2.8-3.7. To reduce aberrations in a lens with such ambitious specifications, these have quite complex constructions, using multiple aspheric elements and often anomalous-dispersion glass. To compensate for the reduced sensitivity of their small sensors, these cameras almost always include an image stabilization system of some kind to enable longer handheld exposures.

These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the reflex viewing system of DSLRs, have so far been fitted with fixed (non-interchangeable) lenses (although in some cases accessory wide-angle or telephoto converters can be attached to the lens), can usually take movies with sound, and the scene is composed by viewing either the liquid crystal display or the electronic viewfinder (EVF). They are usually slower to operate than a true digital SLR, but they are capable of very good image quality (with sufficient light) while being more compact and lighter than DSLRs. The high-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of these cameras can store images in lossless RAW format as an option to JPEG compression. The majority have a built-in flash similar to those found in DSLRs.

[edit] Digital single lens reflex cameras
Main article: Digital single-lens reflex camera

Digital single-lens reflex cameras (DSLRs) are digital cameras based on film single-lens reflex cameras (SLRs). They take their name from their unique viewing system, in which a mirror reflects light from the lens through a separate optical viewfinder. In order to capture an image the mirror is flipped out of the way, allowing light to fall on the imager. Since no light reaches the imager during framing, autofocus is accomplished using specialized sensors in the mirror box itself. Most 21st century DSLRs also have a "live view" mode that emulates the live preview system of compact cameras, when selected.

These cameras have much larger sensors than the other types, typically 18 mm to 36 mm on the diagonal (crop factor 2, 1.6, or 1). This gives them superior low-light performance, less depth of field at a given aperture, and a larger size.

They make use of interchangeable lenses; each major DSLR manufacturer also sells a line of lenses specifically intended to be used on their cameras. This allows the user to select a lens designed for the application at hand: wide-angle, telephoto, low-light, etc. So each lens does not require its own shutter, DSLRs use a focal-plane shutter in front of the imager, behind the mirror.

The mirror flipping out of the way at the moment of exposure makes a distinctive "clack" sound.

[edit] Electronic viewfinder, interchangeable lens cameras
Main article: Micro Four Thirds

In late 2008 a new type of camera emerged, combining the larger sensors and interchangeable lenses of DSLRs with the live preview viewing system of compact cameras, either through an electronic viewfinder or on the rear LCD. These are simpler and more compact than DSLRs due to the removal of the mirror box, and typically emulate the handling and ergonomics of either DSLRs or compacts. As of 2009 the only such system is Micro Four Thirds, borrowing components from the Four Thirds DSLR system.

[edit] Digital rangefinders
Main article: Rangefinder camera#Digital rangefinder

A rangefinder is a user-operated optical mechanism to measure subject distance once widely used on film cameras. Most digital cameras measure subject distance automatically using acoustic or electronic techniques, but it is not customary to say that they have a rangefinder. The term rangefinder alone is sometimes used to mean a rangefinder camera, that is, a film camera equipped with a rangefinder, as distinct from an SLR or a simple camera with no way to measure distance.

[edit] Line-scan camera systems

A line-scan camera is a camera device containing a line-scan image sensor chip, and a focusing mechanism. These cameras are almost solely used in industrial settings to capture an image of a constant stream of moving material. Unlike video cameras, line-scan cameras use a single array of pixel sensors, instead of a matrix of them. Data coming from the line-scan camera has a frequency, where the camera scans a line, waits, and repeats. The data coming from the line-scan camera is commonly processed by a computer, to collect the one-dimensional line data and to create a two-dimensional image. The collected two-dimensional image data is then processed by image-processing methods for industrial purposes.

Line-scan technology is capable of capturing data extremely fast, and at very high image resolutions. Usually under these conditions, resulting collected image data can quickly exceed 100 MB in a fraction of a second. Line-scan-camera–based integrated systems, therefore are usually designed to streamline the camera's output in order to meet the system's objective, using computer technology which is also affordable.

Line-scan cameras intended for the parcel handling industry can integrate adaptive focusing mechanisms to scan six sides of any rectangular parcel in focus, regardless of angle, and size. The resulting 2-D captured images could contain, but are not limited to 1D and 2D barcodes, address information, and any pattern that can be processed via image processing methods. Since the images are 2-D, they are also human-readable and can be viewable on a computer screen. Advanced integrated systems include video coding and optical character recognition (OCR).

[edit] Integration

Many devices include digital cameras built into or integrated into them. For example, mobile phones often include digital cameras; those that do are sometimes known as camera phones. Other small electronic devices (especially those used for communication) such as PDAs, laptops and BlackBerry devices often contain an integral digital camera, as do some some digital camcorders.

Due to the limited storage capacity and general emphasis on convenience rather than image quality, the vast majority of these integrated or converged devices store images in the lossy but compact JPEG file format.

Mobile phones incorporating digital cameras were introduced in Japan in 2001 by J-Phone. In 2003 camera phones outsold stand-alone digital cameras, and in 2006 they outsold all film-based cameras and digital cameras combined. These camera phones reached a billion devices sold in only five years, and by 2007 more than half of the installed base of all mobile phones were camera phones.

Integrated cameras tend to be at the very lowest end of the scale of digital cameras in technical specifications, such as resolution, optical quality, and ability to use accessories. With rapid development, however, the gap between mainstream compact digital cameras and camera phones is closing, and high-end camera phones are competitive with low end stand-alone digital cameras of the same generation.

[edit] Conversion of film cameras to digital
Digital single-lens reflex camera

When digital cameras became common, a question many photographers asked was whether their film cameras could be converted to digital. The answer was yes and no. For the majority of 35 mm film cameras the answer is no, the reworking and cost would be too great, especially as lenses have been evolving as well as cameras. For most a conversion to digital, to give enough space for the electronics and allow a liquid crystal display to preview, would require removing the back of the camera and replacing it with a custom built digital unit.

Many early professional SLR cameras, such as the NC2000 and the Kodak DCS series, were developed from 35 mm film cameras. The technology of the time, however, meant that rather than being a digital "backs" the bodies of these cameras were mounted on large, bulky digital units, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.

A notable exception is the Nikon E2, a camera followed by Nikon E3, using additional optics to convert the 35mm format to a 2/3 CCD-sensor.

A few 35 mm cameras have had digital camera backs made by their manufacturer, Leica being a notable example. Medium format and large format cameras (those using film stock greater than 35 mm), have a low unit production, and typical digital backs for them cost over $10,000. These cameras also tend to be highly modular, with handgrips, film backs, winders, and lenses available separately to fit various needs.

The very large sensor these backs use leads to enormous image sizes. The largest in early 2006 is the Phase One's P45 39 MP imageback, creating a single TIFF image of size up to 224.6 MB. Medium format digitals are geared more towards studio and portrait photography than their smaller DSLR counterparts; the ISO speed in particular tends to have a maximum of 400, versus 6400 for some DSLR cameras.

[edit] History

[edit] Early development

The concept of digitizing images on scanners, and the concept of digitizing video signals, predate the concept of making still pictures by digitizing signals from an array of discrete sensor elements. Eugene F. Lally of the Jet Propulsion Laboratory described a mosaic photosensor at a 1961 space conference.[2]

Texas Instruments engineer Willis Adcock designed a filmless camera and applied for a patent in 1972, but it is not known whether it was ever built.[3] The first recorded attempt at building a digital camera was in 1975 by Steven Sasson, an engineer at Eastman Kodak.[4] It used the then-new solid-state CCD image sensor chips developed by Fairchild Semiconductor in 1973.[5] The camera weighed 8 pounds (3.6 kg), recorded black and white images to a cassette tape, had a resolution of 0.01 megapixels (10,000 pixels), and took 23 seconds to capture its first image in December 1975. The prototype camera was a technical exercise, not intended for production.

[edit] Analog electronic cameras
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Handheld electronic cameras, in the sense of a device meant to be carried and used like a handheld film camera, appeared in 1981 with the demonstration of the Sony Mavica (Magnetic Video Camera). This is not to be confused with the later cameras by Sony that also bore the Mavica name. This was an analog camera, in that it recorded pixel signals continuously, as videotape machines did, without converting them to discrete levels; it recorded television-like signals to a 2 × 2 inch "video floppy".[6] In essence it was a video movie camera that recorded single frames, 50 per disk in field mode and 25 per disk in frame mode. The image quality was considered equal to that of then-current televisions.

Analog electronic cameras do not appear to have reached the market until 1986 with the Canon RC-701. Canon demonstrated a prototype of this model at the 1984 Summer Olympics, printing the images in the Yomiuri Shimbun, a Japanese newspaper. In the United States, the first publication to use these cameras for real reportage was USA Today, in its coverage of World Series baseball. Several factors held back the widespread adoption of analog cameras; the cost (upwards of $20,000), poor image quality compared to film, and the lack of quality affordable printers. Capturing and printing an image originally required access to equipment such as a frame grabber, which was beyond the reach of the average consumer. The "video floppy" disks later had several reader devices available for viewing on a screen, but were never standardized as a computer drive.

The early adopters tended to be in the news media, where the cost was negated by the utility and the ability to transmit images by telephone lines. The poor image quality was offset by the low resolution of newspaper graphics. This capability to transmit images without a satellite link was useful during the Tiananmen Square protests of 1989 and the first Gulf War in 1991.

US government agencies also took a strong interest in the still video concept, notably the US Navy for use as a real time air-to-sea surveillance system.

The first analog camera marketed to consumers may have been the Canon RC-250 Xapshot in 1988. A notable analog camera produced the same year was the Nikon QV-1000C, designed as a press camera and not offered for sale to general users, which sold only a few hundred units. It recorded images in greyscale, and the quality in newspaper print was equal to film cameras. In appearance it closely resembled a modern digital single-lens reflex camera. Images were stored on video floppy disks.

[edit] The arrival of true digital cameras
Nikon D1 digital camera of 1999

The first true digital camera that recorded images as a computerized file was likely the Fuji DS-1P of 1988, which recorded to a 16 MB internal memory card that used a battery to keep the data in memory. This camera was never marketed in the United States, and has not been confirmed to have shipped even in Japan.

The first commercially available digital camera was the 1990 Dycam Model 1; it also sold as the Logitech Fotoman. It used a CCD image sensor, stored pictures digitally, and connected directly to a computer for download.[7][8][9]

In 1991, Kodak brought to market the Kodak DCS-100, the beginning of a long line of professional Kodak DCS SLR cameras that were based in part on film bodies, often Nikons. It used a 1.3 megapixel sensor and was priced at $13,000.

The move to digital formats was helped by the formation of the first JPEG and MPEG standards in 1988, which allowed image and video files to be compressed for storage. The first consumer camera with a liquid crystal display on the back was the Casio QV-10 in 1995, and the first camera to use CompactFlash was the Kodak DC-25 in 1996.

The marketplace for consumer digital cameras was originally low resolution (either analog or digital) cameras built for utility. In 1997 the first megapixel cameras for consumers were marketed. The first camera that offered the ability to record video clips may have been the Ricoh RDC-1 in 1995.

1999 saw the introduction of the Nikon D1, a 2.74 megapixel camera that was the first digital SLR developed entirely by a major manufacturer, and at a cost of under $6,000 at introduction was affordable by professional photographers and high end consumers. This camera also used Nikon F-mount lenses, which meant film photographers could use many of the same lenses they already owned.

[edit] Image resolution

The resolution of a digital camera is often limited by the camera sensor (typically a CCD or CMOS sensor chip) that turns light into discrete signals, replacing the job of film in traditional photography. The sensor is made up of millions of "buckets" that essentially count the number of photons that strike the sensor. This means that the brighter the image at a given point on the sensor, the larger the value that is ready for that pixel. Depending on the physical structure of the sensor, a color filter array may be used which requires a demosaicing/interpolation algorithm. The number of resulting pixels in the image determines its "pixel count". For example, a 640x480 image would have 307,200 pixels, or approximately 307 kilopixels; a 3872x2592 image would have 10,036,224 pixels, or approximately 10 megapixels.

The pixel count alone is commonly presumed to indicate the resolution of a camera, but this is a misconception. There are several other factors that impact a sensor's resolution. Some of these factors include sensor size, lens quality, and the organization of the pixels (for example, a monochrome camera without a Bayer filter mosaic has a higher resolution than a typical color camera). Many digital compact cameras are criticized for having excessive pixels. Sensors can be so small that their 'buckets' can easily overfill; again, resolution of a sensor can become greater than the camera lens could possibly deliver.
Australian recommended retail price of Kodak digital cameras.

As the technology has improved, costs have decreased dramatically. Counting the "pixels per dollar" as a basic measure of value for a digital camera, there has been a continuous and steady increase in the number of pixels each dollar buys in a new camera, in accord with the principles of Moore's Law. This predictability of camera prices was first presented in 1998 at the Australian PMA DIMA conference by Barry Hendy and since referred to as "Hendy's Law".[10]

Since only a few aspect ratios are commonly used (especially 4:3 and 3:2), the number of sensor sizes that are useful is limited. Furthermore, sensor manufacturers do not produce every possible sensor size, but take incremental steps in sizes. For example, in 2007 the three largest sensors (in terms of pixel count) used by Canon were the 21.1, 16.6, and 12.8 megapixel CMOS sensors. The following is a table of sensors commercially used in digital cameras.

Width Height Aspect ratio Actual pixel count Megapixels Camera examples
320 240 4:3 aspect ratio 76,800 0.01 Steven Sasson Prototype (1975)
640 480 4:3 aspect ratio 307,200 0.3 Apple QuickTake 100 (1994)
832 608 4:3 aspect ratio 505,856 0.5 Canon Powershot 600 (1996)
1,024 768 4:3 aspect ratio 786,432 0.8 Olympus D-300L (1996)
1,280 960 4:3 aspect ratio 1,228,800 1.3 Fujifilm DS-300 (1997)
1,280 1,024 5:4 1,310,720 1.3 Fujifilm MX-700 / Leica Digilux (1998), Fujifilm MX-1700 (1999) / Leica Digilux Zoom (2000)
1,600 1,200 4:3 aspect ratio 1,920,000 2 Nikon Coolpix 950
2,012 1,324 3:2 aspect ratio 2,663,888 2.74 Nikon D1
2,048 1,536 4:3 aspect ratio 3,145,728 3 Canon PowerShot A75, Nikon Coolpix 995
2,272 1,704 4:3 aspect ratio 3,871,488 4 Olympus Stylus 410, Contax i4R (although CCD is actually square 2,272x2,272)
2,464 1,648 3:2 aspect ratio 4,060,672 4.1 Canon 1D
2,640 1,760 3:2 aspect ratio 4,646,400 × 3 4.7 × 3 (14.1 MP) Sigma SD14, Sigma DP1 (3 layers of pixels, 4.7 MP per layer, in Foveon X3 sensor)
2,560 1,920 4:3 aspect ratio 4,915,200 5 Olympus E-1, Sony Cyber-shot DSC-F707
2,816 2,112 4:3 aspect ratio 5,947,392 6 Olympus Stylus 600 Digital
3,008 2,000 3:2 aspect ratio 6,016,000 6 Nikon D40, D50, D70, D70s, Pentax K100D
3,072 2,048 3:2 aspect ratio 6,291,456 6.3 Canon 300D, Canon 10D
3,072 2,304 4:3 aspect ratio 7,077,888 7 Olympus FE-210
3,456 2,304 3:2 aspect ratio 7,962,624 8 Canon 350D
3,264 2,448 4:3 aspect ratio 7,990,272 8 Olympus E-500, Olympus SP-350, Canon PowerShot A720 IS
3,504 2,336 3:2 aspect ratio 8,185,344 8.2 Canon 30D, Canon 1D II, Canon 1D II N
3,520 2,344 3:2 aspect ratio 8,250,880 8.25 Canon 20D
3,648 2,736 4:3 aspect ratio 9,980,928 10 Olympus E-410, Olympus E-510, Panasonic FZ50
3,872 2,592 3:2 aspect ratio 10,036,224 10 Nikon D40x, Nikon D60, Nikon D200, Nikon D80, Pentax K10D, Sony Alpha A100
3,888 2,592 3:2 aspect ratio 10,077,696 10.1 Canon 400D, Canon 40D
4,064 2,704 3:2 aspect ratio 10,989,056 11 Canon 1Ds
4,000 3,000 4:3 aspect ratio 12,000,000 12 Canon Powershot G9, Fujifilm FinePix F100fd
4,032 3,024 4:3 aspect ratio 12,192,768 12.3 Olympus PEN E-P1
4,256 2,832 3:2 aspect ratio 12,052,992 12.1 Nikon D3, Nikon D700
4,272 2,848 3:2 aspect ratio 12,166,656 12.2 Canon 450D
4,288 2,848 3:2 aspect ratio 12,212,224 12.2 Nikon D2Xs/D2X, Nikon D300, Nikon D90
4,368 2,912 3:2 aspect ratio 12,719,616 12.7 Canon 5D
4,672 3,104 3:2 aspect ratio 14,501,888 14.5 Pentax K20D
4,992 3,328 3:2 aspect ratio 16,613,376 16.6 Canon 1Ds II
5,616 3,744 3:2 aspect ratio 21,026,304 21.0 Canon 1Ds III, Canon 5D Mark II
6,048 4,032 3:2 aspect ratio 24,385,536 24.4 Sony α 850, Sony α 900, Nikon D3X
7,500 5,000 3:2 aspect ratio 37,500,000 37.5 Leica S2
7,212 5,142 4:3 aspect ratio 39,031,344 39.0 Hasselblad H3DII-39
8,176 6,132 4:3 aspect ratio 50,135,232 50.1 Hasselblad H3DII-50
8,984 6,732 4:3 aspect ratio 60,480,288 60.5 Phase One P65+

[edit] Methods of image capture
At the heart of a digital camera is a CCD image sensor.
This digital camera is partly disassembled. The lens assembly (bottom right) is partially removed, but the sensor (top right) still captures a usable image, as seen on the LCD screen (bottom left).

Since the first digital backs were introduced, there have been three main methods of capturing the image, each based on the hardware configuration of the sensor and color filters.

The first method is often called single-shot, in reference to the number of times the camera's sensor is exposed to the light passing through the camera lens. Single-shot capture systems use either one CCD with a Bayer filter mosaic, or three separate image sensors (one each for the primary additive colors red, green, and blue) which are exposed to the same image via a beam splitter.

The second method is referred to as multi-shot because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique. The most common originally was to use a single image sensor with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method utilized a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to "stitch" together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without a Bayer filter on the chip.

The third method is called scanning because the sensor moves across the focal plane much like the sensor of a desktop scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. In some cases, scanning is accomplished by rotating the whole camera; a digital rotating line camera offers images of very high total resolution.

The choice of method for a given capture is determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject that moves with anything but a single-shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scanning backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.

Dramatic improvements in single-shot cameras and RAW image file processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.

[edit] Filter mosaics, interpolation, and aliasing
The Bayer arrangement of color filters on the pixel array of an image sensor.

In most current consumer digital cameras, a Bayer filter mosaic is used, in combination with an optical anti-aliasing filter to reduce the aliasing due to the reduced sampling of the different primary-color images. A demosaicing algorithm is used to interpolate color information to create a full array of RGB image data.

Cameras that use a beam-splitter single-shot 3CCD approach, three-filter multi-shot approach, or Foveon X3 sensor do not use anti-aliasing filters, nor demosaicing.

Firmware in the camera, or a software in a raw converter program such as Adobe Camera Raw, interprets the raw data from the sensor to obtain a full color image, because the RGB color model requires three intensity values for each pixel: one each for the red, green, and blue (other color models, when used, also require three or more values per pixel). A single sensor element cannot simultaneously record these three intensities, and so a color filter array (CFA) must be used to selectively filter a particular color for each pixel.

The Bayer filter pattern is a repeating 2×2 mosaic pattern of light filters, with green ones at opposite corners and red and blue in the other two positions. The high proportion of green takes advantage of properties of the human visual system, which determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation. Sometimes a 4-color filter pattern is used, often involving two different hues of green. This provides potentially more accurate color, but requires a slightly more complicated interpolation process.

The color intensity values not captured for each pixel can be interpolated (or guessed) from the values of adjacent pixels which represent the color being calculated.

[edit] Connectivity

[edit] Saving photos

Many digital cameras can connect directly to a computer to transfer data:

* Early cameras used the PC serial port. USB is now the most widely used method (most cameras are viewable as USB mass storage), though some have a FireWire port. Some cameras use USB PTP mode for connection instead of USB MSC; some offer both modes.
* Other cameras use wireless connections, via Bluetooth or IEEE 802.11 WiFi, such as the Kodak EasyShare One.
* Cameraphones and some high-end stand-alone digital cameras also use cellular networks to connect for sharing images. The most common standard on cellular networks is the MMS MultiMedia Service, commonly called "picture messaging" which is used by 1.3 billion people. The second method on cellular networks is to send a picture as an email attachment. Only a small percentage of all cameraphones support email so this is not nearly as common.

A common alternative is the use of a card reader which may be capable of reading several types of storage media, as well as high speed transfer of data to the computer. Use of a card reader also avoids draining the camera battery during the download process, as the device takes power from the USB port. An external card reader allows convenient direct access to the images on a collection of storage media. But if only one storage card is in use, moving it back and forth between the camera and the reader can be inconvenient.

[edit] Printing photos

Many modern cameras support the PictBridge standard, which allows them to send data directly to a PictBridge-capable computer printer without the need for a computer.

Wireless connectivity can also provide for printing photos without a cable connection.

Polaroid has introduced a printer integrated into its digital camera which creates a small, printed copy of a photo. This is reminiscent of the original instant camera, popularized by Polaroid in 1975.[11]

[edit] Displaying photos

Many digital cameras include a video output port. Usually sVideo, it sends a standard-definition video signal to a television, allowing the user to show one picture at a time. Buttons or menus on the camera allow the user to select the photo, advance from one to another, or automatically send a "slide show" to the TV.

HDMI has been adopted by many high-end digital camera makers, to show photos in their high-resolution quality on an HDTV.

In January 2008, Silicon Image announced a new technology for sending video from mobile devices to a television in digital form. MHL sends pictures as a video stream, up to 1080p resolution, and is compatible with HDMI.[12]

Some DVD recorders and television sets can read memory cards used in cameras; alternatively several types of flash card readers have TV output capability.

[edit] Modes

Many digital cameras have preset modes for different applications. Within the constraints of correct exposure various parameters can be changed, including exposure, aperture, focusing, light metering, white balance, and equivalent sensitivity. For example a portrait might use a wider aperture to render the background out of focus, and would seek out and focus on a human face rather than other image content.

[edit] Image data storage