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A digital camera is an electronic device used to capture and store photographs digitally, instead of using photographic film like conventional cameras, or recording images in an analog format to magnetic tape like many video cameras.
Modern compact digital cameras are typically multifunctional, with some devices capable of recording sound and/or video as well as photographs. In the Western market, digital cameras now outsell their 35 mm film counterparts. Compact digital cameras Also called digicams, this encompasses most digital cameras. They are characterized by great ease in operation and easy focusing; this design allows for limited motion picture capability. They tend to have significantly smaller zooms than bridge and DSLR cameras. They have an extended depth of field. This allows objects at a larger range of depths to be in focus, which accounts for much of their ease of use. They excel in landscape photography and casual use. They typically save pictures in only the JPEG file format. All but the cheapest models have a built-in flash, although its guide number tends to be very low, perhaps just 6 or 8. The build quality of these small cameras is often very weak and sensitive to drops and knocks. Many find those with a protruding telescopic lens tend to jam on impact or obstruction, even with reputable manufacturers such as Canon the infamous E18 error is well documented on the internet. The arrival of true digital cameras 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 PC for download. In 1991, Kodak brought to market the Kodak DCS-100, the beginning of a long line of professional SLR cameras by Kodak 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. Also in 1999, Minolta introduced the RD-3000 D-SLR at 2.7 megapixels. This camera found many professional adherents. Limitations to the system included the need to use Vectis lenses which were designed for APS size film. The camera was sold with 5 lenses at various focal lengths and ranges (zoom). Minolta did not produce another D-SLR until September 2004 when they introduced the Alpha 7D (Alpha in Japan, Maxxum in North America, Dynax in the rest of the world) but using the Minolta A-mount system from its 35 mm line of cameras. 2003 saw the introduction of the Canon 300D, also known as the Digital Rebel, a 6 megapixel camera and the first DSLR priced under $1,000, and marketed to consumers. Image resolution The resolution of a digital camera is often limited by the camera sensor (usually a charge-coupled device or CCD 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 collect charge in response to light. Generally, these buckets respond to only a narrow range of light wavelengths, due to a color filter over each. Each one of these buckets is called a pixel, and a demosaicing/interpolation algorithm is needed to turn the image with only one wavelength range per pixel into an RGB image where each pixel is three numbers to represent a complete color. The one attribute most commonly compared on cameras is the pixel count. Due to the ever increasing sizes of sensors, the pixel count is into the millions, and using the SI prefix of mega- (which means 1 million) the pixel counts are given in megapixels. For example, an 8.0 megapixel camera has 8.0 million pixels. 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, in that the sensors can be so small that the resolution of the sensor is greater than the lens could possibly deliver. As the technology has improved, costs have decreased dramatically. Measuring 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 consistent 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". Connectivity 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 Wi-Fi, such as the Kodak EasyShare One. 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. Many modern cameras offer the PictBridge standard, which allows sending data directly to printers without the need of a computer. Storage Digital cameras need memory to store data. A wide variety of storage media has been used. These include: Onboard flash memory Cheap cameras and cameras secondary to the device's main use (such as a camera phone). 3.5" floppy disks Mainly the Sony Mavica line of the late 1990s. Video Floppy A 2x2 inch (50 mm � 50 mm) floppy disk used for early analog cameras. PC Card hard drives Early professional cameras, discontinued. CD single or DVD a 185 MB small form factor CD, most commonly seen in the Sony CD-1000. Thermal printer Known only in one model of camera that printed images immediately rather than storing. Memory cards CompactFlash cards/Microdrives Typically higher end professional cameras. The microdrives are actual hard drives in the CompactFlash form factor. Adapters exist to allow using SD cards in a CompactFlash device. CompactFlash cards are much larger than most cards, but have an extremely quick data transfer time. Memory Stick A proprietary flash memory type manufactured by Sony. SD/MMC A flash memory card in a small form factor that is gradually supplanting CompactFlash. The original storage limit was 2 GB, which is being supplanted by 4 GB cards. 4 GB cards are not recognized in all cameras as a revision was made to the SD standard as SDHC (SD High Capacity). The cards also have to be formatted in the FAT32 file format while many older cameras use FAT16 which has a 2 GB partition limit. MiniSD Card A smaller (slightly less than half-size) card used in devices such as camera phones. MicroSD Card A smaller yet (less than a quarter size) version of the SD card. Used in camera phones. xD-Picture Card Developed by Fuji and Olympus in 2002, a format smaller than an SD card. SmartMedia A now obsolete format that competed with CompactFlash, and was limited to 128 MB in capacity. One of the major differences was that SmartMedia had the memory controller built in the reading device, while in CompactFlash it was in the card. The xD picture card was developed as a replacement for SmartMedia. FP Memory A 2-4 MB serial flash memory, known from the Mustek/Relisys Dimera low end cameras. Batteries Digital cameras have high power requirements, and over time have become increasingly smaller in size, which has resulted in an ongoing need to develop a battery small enough to fit in the camera and yet able to power it for a reasonable length of time. Essentially two broad divisions exist in the types of batteries digital cameras use. Formats Main article: Image file formats Common formats for digital camera images are the Joint Photography Experts Group standard (JPEG) and Tagged Image File Format (TIFF). Many cameras, especially professional or DSLR cameras, support a Raw format. A raw image is the unprocessed set of pixel data directly from the camera's sensor. They are often saved in formats proprietary to each manufacturer, such as NEF for Nikon, CR2 for Canon, and MRW for Minolta. Adobe Systems has released the DNG format, a royalty free raw image format which has been adopted by a few camera manufacturers. Raw files initially had to be processed in specialized image editing programs, but over time many mainstream editing programs have added support for them, such as Google's Picasa. Editing raw format images allows much more flexibility in settings such as white balance, exposure compensation, color temperature, and so on. In essence raw format allows the photographer make major adjustments without losing image quality that would otherwise require retaking the picture. Formats for movies are AVI, DV, MPEG, MOV (often containing motion JPEG), WMV, and ASF (basically the same as WMV). Recent formats include MP4, which is based on the QuickTime format and uses newer compression algorithms to allow longer recording times in the same space. Other formats that are used in cameras but not for pictures are the Design Rule for Camera Format (DCF), an ISO specification for the camera's internal file structure and naming, Digital Print Order Format (DPOF), which dictates what order images are to be printed in and how many copies, and the Exchangeable Image File Format (Exif), which uses metadata tags to document the camera settings and date and time for image files. http://en.wikipedia.org/ |
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