(digicam or camera for short) is a camera that takes video or still photographs , or both, digitally by recording images via an electronic image sensor .
Willis Adcock –- a Texas Instruments Engineer, designed a filmless camera that was not digital and applied for a patent in 1972, but it is not known whether it was never built.
The first recorded attempt at building a digital camera was in 1975 by Steven Sasson , an engineer at Eastman Kodak.  It used the then-new solid-state CCD image sensor chips developed by Fairchild Semiconductor in 1973 .
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
Fuji DS-1P of 1988 - The first true digital camera that recorded images as a computerized file, which recorded to a 16 MB internal memory card that used a battery to keep the data in memory.
1990 Dycam Model 1 - The first commercially available digital camera. It also sold as the Logitech Fotoman .
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.
Casio QV -10 of 1995 - The first consumer camera with a liquid crystal display on the back.
Kodak DC -25 in 1996 - the first camera to use Compact Flash
In 1997 the first megapixel cameras for consumers were marketed.
Ricoh RDC -1 in 1995 - The first camera that offered the ability to record video clips.
- is a device that converts an optical image to an electric signal, 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.
- The number of resulting pixels in the image determines its "pixel count“.
A CCD or charged-coupled device is an analog device. When light strikes the chip it is held as a small electrical charge in each photo sensor. The charges are converted to voltage one pixel at a time as they are read from the chip. Additional circuitry in the camera converts the voltage into digital information.
FACTORS THAT IMPACT A SENSOR’S RESOLUTION:
Organization of pixels
METHODS OF IMAGE CAPTURE:
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 addictive colors red, green, and blue) which are exposed to the same image via a beam splitter.
MULTI-SHOT - the sensor is exposed to the image in a sequence of three or more openings of the lens aperture.
MICROSCANNING - This technique utilizes 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.
SCANNING - the sensor moves across the focal plane much like the sensor of a desktop scanner.
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 .
Camera phones 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 camera phones support email so this is not nearly as common.
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.
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.
Some DVD recorders and television sets can read memory cards used in cameras; alternatively several types of flash card readers have TV output capability.
IMAGE DATA STORAGE..
A few cameras use some other form of removable storage such as Microdrives (very small hard disk drives), DC Single (185 MMB), and 3.5” Floppy disks Other unusual formats include:
Onboard flash memory — Cheap cameras and cameras secondary to the device's main use (such as a camera phone)
PC - Card hard drives — early professional cameras (discontinued)
Thermal Printer known only in one model of camera that printed images immediately rather than storing
The Joint Photography Experts Group standard (JPEG) - is the most common file format for storing image data.
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, CRW or CR2 for Canon, and MRW for Minolta.
DNG format - a royalty free raw image format which has been adopted by at least 10 camera manufacturers.
Formats for movies are;
EXIF - data that provides metadata about the picture. It may include aperture, exposure time, focal length, date and time taken, and location .
TYPES OF DIGITAL CAMERA’S
COMPACT DIGITAL CAMERA
- 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“.
- Compacts often have macro capability and zoom lenses but the zoom range is usually less than for bridge and DSLR cameras.
- Bridge or SLR-like cameras are higher-end digital cameras that physically and ergonomically resemble DLSR’s and share with them some advanced features, but share with compacts the use of a fixed lens and a small sensor.
DIGITAL SINGLE-LENS REFLEX CAMERA
- 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.
MICRO FOUR THIRDS CAMERA
- Micro Four Thirds cameras , first unveiled by Panasonic in 2008, are digital single lens reflex-like. Unlike traditional SLRs and DSLRs, they have no reflex mirrors and optical viewfinders. Micro Four Thirds cameras have large sensors like a DSLR and take interchangeable lenses. They are smaller and thinner than most DSLRs. Moderate to high priced.
- A rangefinder is a user-operated optical mechanism to measure subject distance once widely used on film cameras.
- 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.
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.
- 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.
ADVANTAGES OF DIGICAM IN SOFTWARE AND HARDWARE
Manual focus control : Room lights are usually turned out before taking a high-speed flash photograph. In a dark room, a camera in autofocus mode will hunt continuously for something on which to focus. With manual control, the camera can be focused before the lights are turned out.
Manual aperture control : For high-speed flash photography, the flash unit is used off camera. This requires that the camera aperture be set manually for the expected flash exposure on the subject.
Manual shutter control : The shutter is held open in a dark room in readiness for the flash discharge. This usually requires a bulb setting, or, alternatively ...
Shutter durations of at least 1 second : For most high-speed photographic situations, it's possible to initiate the high-speed event in a time period of about a second. For example, for a balloon burst, the shutter button can be depressed and the balloon popped before the shutter closes a second later. This works because human reaction time is typically under a second. Shorter shutter durations can be used successfully, but 1 second provides a margin for error.
Ability to disable the built-in flash : Many digital cameras have built-in flash units. It must be possible to disable this flash. The high-speed event is captured with an external flash.
Override control : Some digital cameras won't allow you to take a picture if the subject is too dark and you're not using the built-in flash. The camera should provide a way to override this annoying feature. If not, there is a way to get around it. A pen light can be shined into the camera's photocell as the shutter is opened.
AC power adapter or rechargeable batteries : Some digital cameras go through batteries quickly. An AC power adapter is a convenient accessory. While having a power cord connected to your camera is inconvenient for candid photography, it's no problem when the camera is mounted on a tripod for high-speed photography. Rechargeable batteries are good if they don't have to be recharged often. The rechargeable lithium batteries that Sony cameras use hold a charge for a long time. Rechargeable AA NiMH batteries used in many digital cameras need more frequent recharging.
SOME OF THE TOP ADVANCED DIGITAL CAMERAS
CANON EOS 20D
The Canon EOS-20D is one of the best digital cameras for the advanced user. With an 8.2 megapixel resolution and a bewildering range of manual modes, this digital SLR will deliver professional looking photos.
CANON POWERSHOT G6
The Canon PowerShot G6 has a 7.1 megapixel resolution, a 4x optical zoom, as well as a wide range of scene modes and manual controls. Even though it lacks a digital SLR body, the images shot with this camera are nothing short of outstanding. It’s also one of the cheapest advanced digital cameras out there.
- The Nikon D70 is one of the best-selling entry level digital SLRs. It has a solid design, a bewildering range of options, powerful speed, as well as great photo quality. With its cheap price, this 6.1 megapixel SLR is one of the best value cameras for serious photographers looking to upgrade their camera.