A digital camera is a camera that takes video or still photographs, or both, digitally by recording images on a light-sensitive sensor.
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 include features that are not found in film cameras, such as displaying an image on the camera's screen immediately after it is recorded, the capacity to take thousands of images on a single small memory device, the ability to record video with sound, the ability to edit images, and deletion of images allowing re-use of the storage they occupied. 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 cameras.
Contents[hide]
1 Classification
1.1 Video cameras
1.2 Live-preview digital cameras
1.2.1 Compact digital cameras
1.2.2 Bridge cameras
1.3 Digital single lens reflex cameras
1.4 Digital rangefinders
1.5 Professional modular digital camera systems
1.6 Line-scan camera systems
2 Conversion of film cameras to digital
3 History
3.1 Early development
3.2 Analog electronic cameras
3.3 The arrival of true digital cameras
4 Image resolution
5 Methods of image capture
6 Filter mosaics, interpolation, and aliasing
7 Connectivity
8 Modes
9 Integration
10 Image data storage
11 Batteries
11.1 Off-the-shelf
11.2 Proprietary
12 Formats
13 See also
14 References
15 External links
//
[edit] Classification
Digital cameras can be classified into several categories:
[edit] Video cameras
Video cameras are classified as devices to record moving images.
Professional video cameras such as those used in television and movie production. These typically have multiple image sensors (one per color) to enhance resolution and color gamut. Professional video cameras usually do not have a built-in VCR or microphone.
Camcorders used by amateurs. They generally include a microphone to record sound, and feature a small liquid crystal display to watch the video during taping and playback.
Webcams are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.
In addition, many live-preview digital cameras have a "movie" mode in which images are continuously acquired at a frame rate sufficient for video.
[edit] Live-preview digital cameras
Canon PowerShot A95 with CompactFlash card loaded
Main article: Live-preview digital camera
The term digital still camera (DSC) usually implies a live-preview digital camera, which uses an electronic screen, usually a rear-mounted liquid crystal display, as the principal means of framing and previewing before taking the photograph, and for viewing stored photographs. All use either a charge-coupled device (CCD) or a CMOS image sensor to sense the light intensities across the focal plane.
Many live-preview cameras have a movie mode, and many camcorders can take still photographs. However, still cameras take better still photographs than camcorders, and vice versa; there is still a need for distinct still and motion picture cameras.
Images may be transferred to a computer, printer or other device in a number of ways: the USB mass storage device class makes the camera appear to the computer as if it were a disk drive; the Picture Transfer Protocol (PTP) and its derivatives may be used; Firewire is sometimes supported; and the storage device may simply be removed from the camera and inserted into another device.
Live-preview cameras may be compact or subcompact, or the larger and more sophisticated bridge cameras.
A student taking a picture
Front view of Canon PowerShot A720 IS, shot by itself in front of a mirror
[edit] Compact digital cameras
Compact cameras are designed to be small and portable; the smallest are described as subcompacts. 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. 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. They have a greater depth of field, allowing objects within a large range of distances from the camera to be in sharp focus. They are particularly suitable for casual and "snapshot" use.
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 include features that are not found in film cameras, such as displaying an image on the camera's screen immediately after it is recorded, the capacity to take thousands of images on a single small memory device, the ability to record video with sound, the ability to edit images, and deletion of images allowing re-use of the storage they occupied. 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 cameras.
Contents[hide]
1 Classification
1.1 Video cameras
1.2 Live-preview digital cameras
1.2.1 Compact digital cameras
1.2.2 Bridge cameras
1.3 Digital single lens reflex cameras
1.4 Digital rangefinders
1.5 Professional modular digital camera systems
1.6 Line-scan camera systems
2 Conversion of film cameras to digital
3 History
3.1 Early development
3.2 Analog electronic cameras
3.3 The arrival of true digital cameras
4 Image resolution
5 Methods of image capture
6 Filter mosaics, interpolation, and aliasing
7 Connectivity
8 Modes
9 Integration
10 Image data storage
11 Batteries
11.1 Off-the-shelf
11.2 Proprietary
12 Formats
13 See also
14 References
15 External links
//
[edit] Classification
Digital cameras can be classified into several categories:
[edit] Video cameras
Video cameras are classified as devices to record moving images.
Professional video cameras such as those used in television and movie production. These typically have multiple image sensors (one per color) to enhance resolution and color gamut. Professional video cameras usually do not have a built-in VCR or microphone.
Camcorders used by amateurs. They generally include a microphone to record sound, and feature a small liquid crystal display to watch the video during taping and playback.
Webcams are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.
In addition, many live-preview digital cameras have a "movie" mode in which images are continuously acquired at a frame rate sufficient for video.
[edit] Live-preview digital cameras
Canon PowerShot A95 with CompactFlash card loaded
Main article: Live-preview digital camera
The term digital still camera (DSC) usually implies a live-preview digital camera, which uses an electronic screen, usually a rear-mounted liquid crystal display, as the principal means of framing and previewing before taking the photograph, and for viewing stored photographs. All use either a charge-coupled device (CCD) or a CMOS image sensor to sense the light intensities across the focal plane.
Many live-preview cameras have a movie mode, and many camcorders can take still photographs. However, still cameras take better still photographs than camcorders, and vice versa; there is still a need for distinct still and motion picture cameras.
Images may be transferred to a computer, printer or other device in a number of ways: the USB mass storage device class makes the camera appear to the computer as if it were a disk drive; the Picture Transfer Protocol (PTP) and its derivatives may be used; Firewire is sometimes supported; and the storage device may simply be removed from the camera and inserted into another device.
Live-preview cameras may be compact or subcompact, or the larger and more sophisticated bridge cameras.
A student taking a picture
Front view of Canon PowerShot A720 IS, shot by itself in front of a mirror
[edit] Compact digital cameras
Compact cameras are designed to be small and portable; the smallest are described as subcompacts. 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. 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. They have a greater depth of field, allowing objects within a large range of distances from the camera to be in sharp focus. They are particularly suitable for casual and "snapshot" use.
[edit] Professional modular digital camera systems
This category includes very high end professional equipment that can be assembled from modular components (winders, grips, lenses, etc.) to suit particular purposes. Common makes include Hasselblad and Mamiya. They were developed for medium or large format film sizes, as these captured greater detail and could be enlarged more than 35 mm.
Typically these cameras are used in studios for commercial production; being bulky and awkward to carry they are rarely used in action or nature photography. They can often be converted into either film or digital use by changing out the back part of the unit, hence the use of terms such as a "digital back" or "film back". These cameras are very expensive (up to $40,000) and are typically not used by consumers.
[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 100MB 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] Conversion of film cameras to digital
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 the most part 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 "back" the body was mounted on a large and blocky digital unit, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.
A notable exception was a device called the EFS-1, which was developed by Silicon Film from c. 1998–2001. It was intended to insert into a film camera in the place of film, giving the camera a 1.3 MP resolution and a capacity of 24 shots. Units were demonstrated, and in 2002 the company was developing the EFS-10, a 10 MP device that was more a true digital back.
A few 35 mm cameras have had digital 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 users who are capable of and willing to pay the price a low unit production digital back requires, typically 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.
This category includes very high end professional equipment that can be assembled from modular components (winders, grips, lenses, etc.) to suit particular purposes. Common makes include Hasselblad and Mamiya. They were developed for medium or large format film sizes, as these captured greater detail and could be enlarged more than 35 mm.
Typically these cameras are used in studios for commercial production; being bulky and awkward to carry they are rarely used in action or nature photography. They can often be converted into either film or digital use by changing out the back part of the unit, hence the use of terms such as a "digital back" or "film back". These cameras are very expensive (up to $40,000) and are typically not used by consumers.
[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 100MB 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] Conversion of film cameras to digital
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 the most part 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 "back" the body was mounted on a large and blocky digital unit, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.
A notable exception was a device called the EFS-1, which was developed by Silicon Film from c. 1998–2001. It was intended to insert into a film camera in the place of film, giving the camera a 1.3 MP resolution and a capacity of 24 shots. Units were demonstrated, and in 2002 the company was developing the EFS-10, a 10 MP device that was more a true digital back.
A few 35 mm cameras have had digital 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 users who are capable of and willing to pay the price a low unit production digital back requires, typically 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.
