Digital camera
From ECDL.web
A digital camera (or digicam) is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. Most 21st century cameras are digital.
Digital cameras can do many things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, and deleting images to free storage space. The majority, including most compact cameras, can record moving video with sound as well as still photographs. Some can crop and stitch pictures and perform other elementary image editing. Some have a GPS receiver built in, and can produce geotagged photographs.
The optical system works the same as in film cameras, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film but the image pickup device is electronic rather than chemical. Most digicams, apart from camera phones and a few specialized types, have a standard tripod screw.
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 specialized digital cameras.
[edit] Image resolution
The resolution of a digital camera is often limited by the image 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 read 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 simple figure of merit is a misconception. Other factors impact a sensor's resolution, including sensor size, lens quality, and the organization of the pixels.
[edit] Image data storage
Many camera phones and most separate digital cameras use memory cards having flash memory to store image data. The majority of cards for separate cameras are SD format; many are CompactFlash or other formats.
A few cameras used some other form of removable storage such as Microdrives (very small hard disk drives), CD single (185 MB) and 3.5" floppy disks. Other unusual formats include onboard flash memory (cheap cameras and cameras secondary to the device's main use) and PC Card hard drives (early professional cameras, discontinued).
[edit] Connectivity
Many digital cameras can connect directly to a computer to transfer data.
- USB is now the most widely used method to connect a camera to the computer, most cameras are viewable as USB mass storage.
- Other cameras use wireless connections, via Bluetooth or WiFi, such as the Kodak EasyShare One.
- Mobile phones equipped with built-in cameras (cameraphones) and some high-end stand-alone digital cameras also use cellular networks to connect for sharing images via MMS (Multimedia Messaging Service) or sending a picture as an email attachment.
- 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.