Digital camera

Sony Mavica FD5
Sony Mavica FD5
Sony DSC F 828
Sony DSC F 828

a digital camera, also digital camera mentioned, is a camera, with which the photograph medium film was replaced by an electronic image converter (image sensor) and a digital storage medium.

Table of contents

history

invention phase

the history of the digital camera takes its beginning with the 1963 video disk camera invented by David Paul Gregg at the Stanford University, and although its pictures only a few minutes (on eventhat video disk) to be stored could, then it is nevertheless the first camera, which stores optical pictures digitally.

The first patent on all flat (picture) screens, the optical pictures will be able to keep stably (would solvent-do) to take up and requested 1968. U.S. patent # 3,540,011

In the year 1969 the basis of the CCD (charged coup LED DEVICE) was then invented by wanting pool of broadcasting corporations Boyle and George Smith. The CCD is an photo-sensitive chip, which can be used for many purposes. With the CCD pictures can both stored andalso to be shown and worked on. This invention is the final technical break-through on the way to the digital photography.

1970 builds Bell - scientist the first solvent State video camera those the CCD as image recorder uses. One notes that it itself here still around one Video camera acts, there it more with difficulty was an individual picture to be stored than a small film.

A further important patent becomes 1972 to the inventor Willis A. Adcock spent of Texas Instruments. It describes a filmless, electronic camera, whereby stillPicture monitor as Sucher is recommended.

The CCD became commercially available 1973, which by Fairchild Imaging one developed and one produced. It had a dissolution of 100 × 100 pixels (0.01 megapixels). 1974 found Dr. Gil Amelio a possibility CCDs simplyto manufacture and industrially.

1975 are the birth of the first “correct” digital camera. It was designed by Steve J. Sasson of Kodak. It used the CCD von Fairchild as image sensor, needed 23 seconds around only one picture upa digital cartridge to store and weighed 8 1/2 Pound.

The Fairchild MV-101 was then 1976 the first commercially available CDD camera with evenly that above dissolution of 0,01 megapixels.

further development

digital cameras became starting from center of the 80'sfirst predominantly of professional photographers used in the range of the Studio - , mode - and advertising photography as well as starting from center of the 90's also in the report photography. Early production stage of models Sony ( Mavica ) became and by Apple ( Apple QuickTake), Canon (ion) offered; Konica Minolta (Dimage), Nikon (Coolpix) and Olympus (Camedia) and. A. followed with own model rows. 2002 became for the first time a digital mirror reflex camera (DSLR = digitally single Lens reflex) with oneSensor in full small dimension of picture area of Canon presented.

Within the home user range digital cameras become generally accepted years starting from end of the 1990er and obtain due to rapidly falling prices meanwhile higher conversions than similar photo devices. [1].

With it a stormy stimulation of the entire is connectedPhoto trade, which applied before introduction of the digital cameras as satisfied and technologically expenditure-provoked. Despite initial fears the introduction of digital photographing to no decrease of the quantity of orders in the photo laboratories led. Rather even increases are determined. Also today those wantPhotographer their pictures still on Papierabzügen see.

Digital cameras become since beginning 21. Century increasingly into other devices integrates:

  • Nearly all modern mobile telephones contain an inserted digital camera. Meanwhile also models are also built here to two megapixels.
  • For personnelDigitally Assistants are available external Handy modules, or a simple digital camera is integrated into the PDA.
  • Video Camcorder possesses photo functions, which work similarly as digital cameras.

On the other hand many digital cameras have those the possibility of taking up films to video home system quality with clay/tone orto transfer digital signals without intermediate storage directly to the interface. Thus these digital cameras can be used also as Webcam.

function mode

the photographic picture develops in a digital camera in the following steps:

  1. Focusing the picture
  2. measuring a meaningful exposure timeand screen
  3. optical projection by the objective
  4. optical filtering by infrared and RGB filter
  5. transformation of the light intensities into similar electrical signals in discrete elements (discretisation)
  6. digitization of the signals by analog-digital transformation (quantization)
  7. image processing of the image file:
    1. Color reconstruction
    2. conversion ofTensions in brightness
    3. intoxication filtering
    4. removing well-known errors of the picture recording system (defective pixels, cross modulation, resharpening, edge shading, distortion)
  8. compression of the image file
  9. storage of the image file.

With a digital camera light arrives by a lens, which throws the picture on the sensor, into the Kameragehäuse.Before the sensor the light goes through itself infrared - as well as it thus around a completely similar process.

The A/D transducer accomplishes a picture transformation , which consists of the steps discretisation and quantization.

The discretisation designates the picture dismantling into discrete units.Since with cameras, which after the RGB - system work, per pixel three Farbwerte to be stored must, a color interpolation takes place . The two not registered Farbwerte from the values of the surrounding cells interpolated, i.e. according to a rule“turn out” (educated guess). The color interpolation an averaging is general.

Subsequently, the compression takes place for the reduction of the volume of data, if the picture in the JPEG - compressed or tiff - is stored data format; to what extent raw data (Raw format) are compressed, hangs of prop. guessing eras format of the respective manufacturer off.

picture transformation

as with an analog camera is collected the incident light with an objective and focused on the film level, in this case on the sensor, (focused). The sensor is an electronicElement, which has usually a clearly smaller surface than a picture on similar 35-mm-Film of a 35mm camera; digital cameras only with high order have a sensor in size of the APS - C-negative or even over a full format sensor. Within the professional rangesensor sizes to 36x48 mm are used.

In principle two sensor types are differentiated: Surface sensor and line sensor.

With the surface sensor the CCD registers either at the same time the three basic colours (One SHOT cameras), or successively (Three SHOT cameras). Essentially two different existmarketable surface sensor - types, the CCD sensor (most digital cameras of Sony, Nikon, Konica Minolta, Pentax, Olympus etc.) with the variant super CCD sensor (only Fujifilm) as well as the CMOS sensor.

A privileged position takes the Foveon - sensor, thatin sigma - cameras is used. It concerns a dreischichtigen sensor, which notes red, green and blue light with each sensor element. The interesting principle to the defiance also the second generation did not lead to piercing success.

Line sensors in scanner cameras are used, which function according to the scanner principle, i.e. they work similarly as a flat bed scanner and scan the picture line by line.

image processing

in a digital camera demonstrates electronics a number of picture-changing processing, duringand after the admission through; these are summarized under the term of the image processing. This is to differentiate of the treatment of pictures, which is accomplished at the finished admission.

The digital camera affects by the white alignment - like also the video camera -the Farbtreue with daylight or art light.

The homogeneity, i.e. even sharpness and brightness over the entire picture in particular at the contour, depend on the optics and must become balanced with aberrations by the camera-internal software.

The quality thatcamera-internal electronics decides also on the signal dynamics, i.e. the brightness stages distinguishable of the camera, as well as the Kontrastumfang of the digital picture.

Camera electronics affects also the picture purity and/or. the degrees at picture errors, itself for example as noise or Artifacts show. With cameras with a dissolution of three megapixels and more CCD error cannot be avoided any longer: Individual cells do not work possibly at all, others work against it with different sensitivity etc. Such “misfires” must just like particularly with night photographsarising picture noise of camera electronics become balanced.

For the improvement of the subjective picture effect camera electronics accomplishes beyond that still various optimizations. In addition count for example:

  • Scharfzeichnung: Recognizing and strengthening transitions in the picture;
  • Contrast rise: Rise of the contrast in the picture;
  • Farbsättigung: Increase the Farbsättigung;

Before a photo is released, the autofocus is set on, which takes over the focusing. Even if several photos are made by the same object, a focusing must take place in each case. With some cameras the autofocus can are turned off. One looks for a sharpness shim however in vain with most digital cameras. Only over a menu structure a manual focusing in stages can be achieved, what limits the application type of digital cameras, particularly since the manual focusing functions reliably only with mirror reflex cameras. Alsoif the autofocus is switched off, still another white alignment takes place before releasing in camera electronics. And because that is not enough, also still another black alignment finds instead of to filter (in order the electronic noise of the sensor and error pixel).

Digitally Revio

KD-300Z with retract and extended zoom by the image plane

of the sensor smaller opposite a 35mm camera other focal lengths for the objectives result optical system Konica for same picture angles; this becomes partly falsely than focal length extension and/or. Focal length extension factor designates, althoughthe focal length of the objective is naturally not changed. In order to be able to compare the objectives further in a simple manner with the conventional small display format, many manufacturers of compact digital cameras indicate their objectives additionally to the material focal length also as the focal length, whichin the small display format would achieve the same picture angle.

With digital mirror reflex cameras with change objectives mostly conversion factor indicated - which extension factor so mentioned -, by which the focal length of the objective must be multiplied, in order to calculate the small picture focal length, those the samePicture angle takes up. This has disadvantages within the wide angle range, since there smaller picture pictures result toward normal objective, advantages against it in the Telebereich since the smaller picture angles a stronger Tele mean there.

Additionally to an optical inserted usually with digital compact cameras Many models still another digital zoom shot possess zoom shot. It concerns an interpolation, which lets the picture appear larger, actually takes place itself however only one cutout enlargement with reduced dissolution. Digital zoom shots are not a pure marketing Konstrukt and havephotographic value. The functionally identical effect leaves itself additional and with any enlargement with each picture working on software and/or. “Zoom shot factor” realize.

according to

Suchersysteme their conventional counterparts have digital cameras depending upon construction principle different optical Suchersysteme, the oneOrganization of the picture before the admission make possible.

These are in the Consumersegment of the rule separate optical systems. This structure makes possible to be permanently active the photograph sensor and a preview (“live preview”) on the picture, and. And. together with status information, on thatTo represent monitor of the equipment. In the market segment for the professional use devices in mirror reflex building method are usually manufactured, with which only either the Sucher or the photograph sensor can be construction dependently simultaneous in enterprise. For the fastidious amateur becomeCameras offered, which are to connect the advantages of both systems. This is solved by halfpermeable mirrors or digital Sucher, which are based on a separate display. Professional digital Messucherkamera is underrepresented on the market, it is at present (conditions 2006) only inModel (Epson R-D1) available.

Cameras with integrated monitor have the advantage in common to remove that they permit after the admission to regard the taken up pictures still locally and failed photographs.

performance classes and dissolution

35mm miniature film hasa dissolution of approximately 13 to 200 megapixels. The best objectives reach however only about 20 million pixel. Good zoom shots have approx. 13 million pixel and slide become with approx. 10 million pixels (2700dpi) scanned.

Digital cameras with picture resolution under two Megapixels are considered today as Fun - and/or. Toy cameras or become for special applications (e.g. quick series screen sequences, snapshots) assigned. They are i. D. R. equipped with fixed focus objectives. Among them also micro cameras with VGA dissolution (0.3 megapixels) fall, which can be used as key trailers,as well as most at present available mobile phone - cameras (conditions: 2004).

Sharp TM 200 Fotohandy mit 2 Megapixel Auflösung
Sharp TM 200 Fotohandy with 2 megapixels dissolution

digital cameras with a dissolution of 4-5 megapixels are considered today (2006) as a riser class. They developed to serve inexpensive and easily. They are sufficient forPapierabzüge to 50 cm × 75 cm. Image file sizes lie here around 1 to 2 MT. Unkomprimierte tiff - In addition, pictures can be large 15 MT.

Dissolutions of six to eight megapixels are considered as middle class, High end devices order at present (conditions: 03/2004) overDissolutions of 16 to 39 megapixels; when these dissolutions problem-free all pressure formats are possible (up to the 16/1 poster wall). To note it is however also here that itself the display formats of the camera partly of the classical display formats of the photo laboratories for Papierabzügedifferentiate, so that a trimming takes place.

The professional class offers mirror reflex cameras with change objectives, to extended attitude possibilities as well as with CCD and/or. CMOS sensors with dissolutions starting from approximately 6 megapixels. By the prices of under 700 EUR (conditions: 01/2006) for a combination of housing alsoinexpensive objective, these devices are used in the meantime also by numerous ambitionierten amateurs. The number of pixels is in the professional class of subordinated rank; crucial are rather the quality of the objective and the picture transformation as well as attitude possibilities and photograph speed. Similar central format andSpecialized cameras can be reequipped usually by digital photography modules, with which dissolutions to 39 megapixels are reached.

To the comparison: With the conventional similar small picture photography one speaks of 30 megapixels, which can be obtained with a good film. This dissolutionbecomes for example of the Negativfilm Kodak Ektar 25 Professor. reached (dissolution 200 lines/mm with 1000:1 contrast). Almost any photographic film offers today a dissolution of at least 100 lines per millimeter, a miniature film has therefore a dissolution ofat least 3.600×2.400 pixels, thus about 8.6 megapixels; such comparisons are however problematic for different reasons; see. for this Ausbelichtung and Kodachrome.

In addition, apart from the CCD dissolution the optical system and electronics decide on the total result. These three “columns” togetherresult in the actually relevant dissolution of effective, which can be determined only on the basis test patterns, for example after the Auflösungschart ISO 12233. The dissolution of effective is determined by the weakest in each case “column”.

The border of the dissolution becomes both with the similar anddigital photography by the objectives determines. The best at present (2003) objectives like for example the Leica Summilux r 1:1,4 /80 mm (2003, available on the market: 3,000 euro) have the resolving power of comparable 20 megapixels. A very good zoom like thatCanon 28-70mm f/2.8 (2003: ) A dissolution of approx. has 1,000 euro. 61 lp/mm (pairs of lines/millimeters), which corresponds to about 13 megapixels. Unfortunately with cheap digital cameras mainly at the optics one saves.

For different target groups and - employments are sufficient certain dissolutions:

  • 2-3 megapixels:Snapshots, vacation photo, compact camera replacement,
  • 3-4 megapixels: Departures to maximally DIN A4 - size of,
  • > 5 megapixels: professional employment by designers and commercial artists.

January 2006: Many new digital cameras (also in the inexpensive a riser class) have a dissolution over 5 megapixels. Most current devices with high orderlie between 8 and 10 megapixels. However this high and advertising-effective resolution with further in compact cameras used very small sensors by a partial dramatically bad intoxication behavior bought - the results 10 megapixels of a compact camera is in all rulenot to compare with the quality of an admission mirror reflex with 6 megapixels.

speed

the operating speed of a digital camera is determined particularly by four characteristic characteristics:

  1. Acceptance, thus the time interval, those the digital camera after thatSwitch on necessarily, in order to be able to make a photography;
  2. Release delay, thus the time interval between pressures of the trip and actual picture recording elapses;
  3. Bildfolgezeit, thus the time interval after an admission, after which the camera can make a next screen. In directConnection hereby stands the maximum image frequency of the digital camera.
  4. Focusing speed, thus the time interval, which the autofocus needs for focusing.

Despite a rapid technical development today still almost all digital compact cameras are significantly slower than their equivalents in the small display space (conditions: 2004).Above all the Bildfolgezeiten often break in after few photographs substantial, while with 35mm cameras by means of the entire film away the same speed can be achieved.

The release delay and Bildfolgezeit are however comparable with high-quality digital cameras to its similar counterparts.

power supply

each digital camera needs a continuous power supply, which is usually ensured over a power pack or a Akku; besides there are also some special constructions, which are based for example on solar energy.

Digital cameras need by far more energy thansimilar cameras. This is a large disadvantage of the devices and with transferred to the digital photography to consider. In particular the constant use of an inserted mini monitor and the lightning use are large Stromfresser.

The capacity of the Akkus contributes - to connectionthe capacity of camera electronics and their current savings functions - over the maximum actual working time of the camera, until a Akkuwechsel becomes necessary.

Prop. guessing acres Akkutypen are clearly more expensively than standard Akkus (Mignon AA or AAA etc.), but frequently also more efficient. An average Akku of2000mAh supplies a digital camera for energy for taking up approximately 200 pictures. No nickel cadmium Akkus ( NiCD) should be used, but only high-quality NiMH Akkus with at least 1800mAh. Still lithium ion Akkus longer holding is only for few digital camera types on the market.

Work on []

File format

thereby a picture with one dissolution of two megapixels and three colors per pixel not six megabyte (file size unkomprimierte) on the memory card to write must, it is compressed.

As lossy mode format stands to after EXIF - standard the JPEG -Order, as loss-free mode is offered tiff; besides some cameras with high order can store the digital pictures in prop. guessing eras a raw data format (RAW).

Since for the format of the raw data no standard exists, the graphic data of different camera manufacturers and even different series are oneManufacturer among themselves compatibly and do not have to be converted before the view or treatment by means of an application made available by the camera manufacturer into a standard display format (usually tiff or JPG). Also applications and Plugins for picture working on programs exist of third manufacturers, the RAW data of different camerasto read and process can.

RAW data are called also digital negative. Similarly to the similar photography one can affect outgoing of it many parameters before production of the actual graphic data: Gamma correction, white alignment, brightness, contrast, sharpness. RAW data point due to theirlossless storage no fragments up. A further important advantage is the larger color extent. While JPG pictures with 8-bit for each color are stored, RAW data in 12 or even 14 bits are present. The pictures are present thus in larger color gradations.

Numerous one Cameras offer also the possibility of taking up short video sequences which usually in the Motion JPEG - or Apple QuickTime - format are stored, however due to the picture repeating rate which can be reached usually in lower dissolution than the camera taken up the pictures. The dissolution liesclearly under the values of all usual video cameras. For mirror reflex cameras this possibility is void system-dependently.

Digital cameras embed also Metainformationen so mentioned, which in the EXIF into the graphic data - standard are specified. These EXIF meta data are in the header so mentioned of the image file.Many picture working on programs as well as special Tools can pick out and indicate these data. They can apply also with the Ausbelichtung of the digital picture in photo paper in the photo laboratory.

To the parameters stored via EXIF automatically for each admission belong for example:

storage media

CompactFlash - memory card

to be stored the pictures in the camera on different storage media. Today common above all CompactFlash , MEMORY stick, are Microdrive, SmartMedia, SDMEMORY Card (and/or. the predecessor Multimedia Card) as well as xD-Picture Card; older digital cameras used beside it also floppy disks, PCMCIA -/PC Cards or Compact disks.

the universal has itself device interfaces as hardware interface within the user rangeSerial bus as far as possible interspersed. The camera places the data to the PC usually either as “measure of STORAGE DEVICE” (similarly a USB memory stick) or in the PTP mode for the order. Over the PTP mode is possible with some cameras also the computer controlled release,in the rarest cases however with full control of exposure time, screen, zoom shot, focus and ISO number.

Software interfaces between image input equipment and Bildverarbeitungspogramm

further equipment characteristics

further one relevant equipment characteristics are:

  • Operation
  • dimensions
  • weight
  • luminous intensity of theObjective
  • quality that of objective (aberration)
  • optical zoom shot
  • digital zoom shot
  • white alignment
  • sunlight cover of the display
  • of digital Sucher
  • diopter correction for optical Sucher
  • system speed (series display function, release delay etc.)
  • Akkuart and - capacity
  • interfaces
  • storage medium
  • documentation
  • service and warranty
  • auxiliary functions such as panorama - display function, language recording, video admission,Selbstauslöser, remote maintenance, exposure correction, adjustable sensitivity, Akku Restanzeige
  • integration into an existing camera system, digitally or similar to
  • possible accessories (lightning, objectives, filter, remote release)

offerers

the largest manufacturers of the digital cameras are: Canon, Sony, Konica Minolta, Nikon, Olympus and Kodak. Common also cameras of Agfa , BenQ , are Casio, Contax, Epson, Fujifilm, HP, JVC, Kyocera, Leica, Panasonic, Pentax, Praktica, Ricoh, Rollei, Samsung, Sanyo, sigma and Toshiba.

see also

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