Digital photography is a form of photography that uses cameras containing arrays of electronic photodetectors to capture images focused by a lens, as opposed to an exposure on photographic film. The captured images are digitized and stored as a computer file ready for further digital processing, viewing, digital publishing or printing.
Until the advent of such technology, photographs were made by exposing light sensitive photographic film and paper, which was processed in liquid chemical solutions to develop and stabilize the image. Digital photographs are typically created solely by computer-based photoelectric and mechanical techniques, without wet bath chemical processing.
Digital photography is one of the several forms of digital imaging. Digital images are also created by non-photographic equipment such as computer tomography scanners and radio telescopes. Digital images can also be made by scanning other printed photographic images or negatives.
The first consumer digital cameras were marketed in the late 1990s. Professionals gravitated to digital slowly, and were won over when their professional work required using digital files to fulfill the demands of employers and/or clients, for faster turn-around than conventional methods would allow. Starting around 2007, digital cameras were incorporated in cell phones and in the following years, cell phone cameras became widespread, particularly due to their connectivity to social media websites and email. Since 2010, the digital point-and-shoot and DSLR formats have also seen competition from the mirrorless digital camera format, which typically provides better image quality than the point-and-shoot or cell phone formats but comes in a smaller size and shape than the typical DSLR. Many mirrorless cameras accept interchangeable lenses and have advanced features through an electronic viewfinder, which replaces the through-the-lens finder image of the SLR format.
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The digital camera
History
The first flyby spacecraft image of Mars was taken from Mariner 4 on July 15, 1965, with a camera system designed by NASA/JPL. It used a video camera tube followed by a digitizer, rather than a mosaic of solid state sensor elements, so it was not what we usually define as a digital camera, but it produced a digital image that was stored on tape for later slow transmission back to Earth.
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 (charge-coupled device, a high-speed semiconductor) 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.
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 internationally, 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 computer for downloading images.
Number of photos taken
According to research from KeyPoint Intelligence/InfoTrends, an estimated 400 billion digital photos were taken globally in 2011 and this will rise to 1.2 trillion photos in 2017. An estimated 85 percent of the photos taken in 2017 will be done with the smartphone rather than a traditional digital camera.
Sensors
Image sensors read the intensity of light, and digital memory devices store the digital image information as RGB color space or as raw data.
The two main types of sensors are charge-coupled devices (CCD), in which the photocharge is shifted to a central charge-to-voltage converter, and CMOS or active pixel sensors.
Multifunctionality and connectivity
Except for some linear array type of cameras at the highest-end and simple web cams at the lowest-end, a digital memory device (usually a memory card; floppy disks and CD-RWs are less common) is used for storing images, which may be transferred to a computer later.
Digital cameras can take pictures, and may also record sound and video. Some can be used as webcams, some can use the PictBridge standard to connect to a printer without using a computer, and some can display pictures directly on a television set. Similarly, many camcorders can take still photographs, and store them on videotape or on flash memorycards with the same functionality as digital cameras.
Digital photography is one of the most exceptional instances of the shift from converting conventional analog information to digital information. This shift is so tremendous because it was a chemical and mechanical process and became an all digital process with a built in computer in all digital cameras.
Performance metrics
The quality of a digital image is a composite of various factors, many of which are similar to those of film cameras. Pixel count (typically listed in megapixels, millions of pixels) is only one of the major factors, though it is the most heavily marketed figure of merit. Digital camera manufacturers advertise this figure because consumers can use it to easily compare camera capabilities. It is not, however, the major factor in evaluating a digital camera for most applications. The processing system inside the camera that turns the raw data into a color-balanced and pleasing photograph is usually more critical, which is why some 4+ megapixel cameras perform better than higher-end cameras.
Resolution in pixels is not the only measure of image quality. A larger sensor with the same number of pixels generally produces a better image than a smaller one. One of the most important differences is an improvement in image noise. This is one of the advantages of digital SLR (single-lens reflex) cameras, which have larger sensors than simpler cameras (so-called point and shoot cameras) of the same resolution.
- Lens quality: resolution, distortion, dispersion (see Lens (optics))
- Capture medium: CMOS, CCD, negative film, reversal film etc.
- Capture format: pixel count, digital file type (RAW, TIFF, JPEG), film format (135 film, 120 film, 5x4, 10x8).
- Processing: digital and / or chemical processing of 'negative' and 'print'.
Pixel counts
The number of pixels n for a given maximum resolution (w horizontal pixels by h vertical pixels) is the product n = w × h. This yields e. g. 1.92 megapixels (1,920,000 pixels) for an image of 1600 × 1200. The majority of compact as well as some DSLR cameras have a 4:3 aspect ratio, i.e. w/h = 4/3. According to Digital Photography Review, the 4:3 ratio is because "computer monitors are 4:3 ratio, old CCDs always had a 4:3 ratio, and thus digital cameras inherited this aspect ratio."
The pixel count quoted by manufacturers can be misleading as it may not be the number of full-color pixels. For cameras using single-chip image sensors the number claimed is the total number of single-color-sensitive photosensors, whether they have different locations in the plane, as with the Bayer sensor, or in stacks of three co-located photosensors as in the Foveon X3 sensor. However, the images have different numbers of RGB pixels: Bayer-sensor cameras produce as many RGB pixels as photosensors via demosaicing (interpolation), while Foveon sensors produce uninterpolated image files with one-third as many RGB pixels as photosensors. Comparisons of megapixel ratings of these two types of sensors are sometimes a subject of dispute.
The relative increase in detail resulting from an increase in resolution is better compared by looking at the number of pixels across (or down) the picture, rather than the total number of pixels in the picture area. For example, a sensor of 2560 × 1600 sensor elements is described as "4 megapixels" (2560 × 1600 = 4,096,000). Increasing to 3200 × 2048 increases the pixels in the picture to 6,553,600 (6.5 megapixels), a factor of 1.6, but the pixels per cm in the picture (at the same image size) increases by only 1.25 times. A measure of the comparative increase in linear resolution is the square root of the increase in area resolution, i.e., megapixels in the entire image.
Dynamic range
Practical imaging systems both digital and film, have a limited "dynamic range": the range of luminosity that can be reproduced accurately. Highlights of the subject that are too bright are rendered as white, with no detail; shadows that are too dark are rendered as black. The loss of detail is not abrupt with film, or in dark shadows with digital sensors: some detail is retained as brightness moves out of the dynamic range. "Highlight burn-out" of digital sensors, however, can be abrupt, and highlight detail may be lost. And as the sensor elements for different colors saturate in turn, there can be gross hue or saturation shift in burnt-out highlights.
Some digital cameras can show these blown highlights in the image review, allowing the photographer to re-shoot the picture with a modified exposure. Others compensate for the total contrast of a scene by selectively exposing darker pixels longer. A third technique is used by Fujifilm in its FinePix S3 Pro digital SLR. The image sensor contains additional photodiodes of lower sensitivity than the main ones; these retain detail in parts of the image too bright for the main sensor.
High dynamic range imaging (HDR) addresses this problem by increasing the dynamic range of images by either
- increasing the dynamic range of the image sensor or
- by using exposure bracketing and post-processing the separate images to create a single image with a higher dynamic range.
HDR images curtail burn-outs and black-outs.
Storage
Many camera phones and most digital cameras use memory cards having flash memory to store image data. The majority of cards for separate cameras are SD (Secure Digital) format; many are CompactFlash (CF) and the other formats are rare. XQD card format was the last new form of card, targeted at high-definition camcorders and high-resolution digital photo cameras. Most modern digital cameras also use internal memory for a limited capacity for pictures that can be transferred to or from the card or through the camera's connections; even without a memory card inserted into the camera.
Memory cards can hold vast numbers of photos, requiring attention only when the memory card is full. For most users, this means hundreds of quality photos stored on the same memory card. Images may be transferred to other media for archival or personal use. Cards with high speed and capacity are suited to video and burst mode (capture several photographs in a quick succession).
Because photographers rely on the integrity of image files, it is important to take proper care of memory cards. Common advocacy calls for formatting of the cards after transferring the images onto a computer. However, since all cameras only do quick formatting of cards, it is advisable to carry out a more thorough formatting using appropriate software on a PC once in a while. Effectively, this involves scanning of the cards to search for possible errors.
Captured Photography Video
Market impact
In late 2002, 2-megapixel cameras were available in the United States for less than $100, with some 1-megapixel cameras for under $60. At the same time, many discount stores with photo labs introduced a "digital front end", allowing consumers to obtain true chemical prints (as opposed to ink-jet prints) in an hour. These prices were similar to those of prints made from film negatives. However, because digital images have a different aspect ratio than 35 mm film images, people have started to realize that 4x6 inch prints crop some of the image off the print. Some photofinishers have started offering prints with the same aspect ratio as the digital cameras record.
In July 2003, digital cameras entered the disposable camera market with the release of the Ritz Dakota Digital, a 1.2-megapixel (1280 x 960) CMOS-based digital camera costing only $11 (USD). Following the familiar single-use concept long in use with film cameras, Ritz intended the Dakota Digital for single use. When the pre-programmed 25-picture limit is reached, the camera is returned to the store, and the consumer receives back prints and a CD-ROM with their photos. The camera is then refurbished and resold.
Since the introduction of the Dakota Digital, a number of similar single-use digital cameras have appeared. Most single-use digital cameras are nearly identical to the original Dakota Digital in specifications and function, though a few include superior specifications and more advanced functions (such as higher image resolutions and LCD screens). Most, if not all these single-use digital cameras cost less than $20 (USD), not including processing. However, the huge demand for complex digital cameras at competitive prices has often caused manufacturing shortcuts, evidenced by a large increase in customer complaints over camera malfunctions, high parts prices, and short service life. Some digital cameras offer only a 90-day warranty.
Since 2003, digital cameras have outsold film cameras. Prices of 35mm compact cameras have dropped with manufacturers further outsourcing to countries such as China. Kodak announced in January 2004 that they would no longer sell Kodak-branded film cameras in the developed world. In January 2006, Nikon followed suit and announced they would stop production of all but two models of their film cameras. They will continue to produce the low-end Nikon FM10, and the high-end Nikon F6. In the same month, Konica Minolta announced it was pulling out of the camera business altogether. The price of 35mm and APS (Advanced Photo System) compact cameras have dropped, probably due to direct competition from digital and the resulting growth of the offer of second-hand film cameras. Pentax have reduced production of film cameras but not halted it. The technology has improved so rapidly that one of Kodak's film cameras was discontinued before it was awarded a "camera of the year" award later in the year. The decline in film camera sales has also led to a decline in purchases of film for such cameras. In November 2004, a German division of Agfa-Gevaert, AgfaPhoto, split off. Within six months it filed for bankruptcy. Konica Minolta Photo Imaging, Inc. ended production of Color film and paper worldwide by March 31, 2007. In addition, by 2005, Kodak employed less than a third of the employees it had twenty years earlier. It is not known if these job losses in the film industry have been offset in the digital image industry. Digital cameras have decimated the film photography industry through declining use of the expensive film rolls and development chemicals previously required to develop the photos. This has had a dramatic effect on companies such as Fuji, Kodak, and Agfa. Many stores that formerly offered photofinishing services or sold film no longer do, or have seen a tremendous decline. In 2012, Kodak filed for bankruptcy after struggling to adapt to the changing industry.(See Photographic film)
In addition, digital photography has resulted in some positive market impacts as well. The increasing popularity of products such as digital photo frames and canvas prints is a direct result of the increasing popularity of digital photography.
Digital camera sales peaked in March 2012 averaging about 11 million units a month, but sales have declined significantly ever since. By March 2014, about 3 million were purchased each month, about 30 percent of the peak sales total. The decline may have bottomed out, with sales average hovering around 3 million a month. The main competitor is smartphones, most of which have built-in digital cameras, which routinely get better. They also offer the ability to record videos.
Social impact
Until the advent of the digital camera, amateur photographers could either buy print or slide film for their cameras. Slides could be developed and shown to an audience using a slide projector. Digital photography revolutionized the industry by eliminating the delay and cost. The ease of viewing, transferring, editing and distributing allowed consumers to manage their digital photos with ordinary home computers rather than specialized equipment.
Camera phones, being the majority of cameras, have arguably the largest impact. The user can set their Smartphones to upload their products to the Internet, preserving them even if the camera is destroyed or the images deleted. Some high street photography shops have self-service kiosks that allow images to be printed directly from smartphones via Bluetooth technology.
Archivists and historians have noticed the transitory nature of digital media. Unlike film and print, which are tangible and immediately accessible to a person, digital image storage is ever-changing, with old media and decoding software becoming obsolete or inaccessible by new technologies. Historians are concerned that we are creating a historical void where information and details about an era would have been lost within either failed or inaccessible digital media. They recommend that professional and amateur users develop strategies for digital preservation by migrating stored digital images from old technologies to new. Scrapbookers who may have used film for creating artistic and personal memoirs may need to modify their approach to digital photo books to personalize them and retain the special qualities of traditional photo albums.
The web has been a popular medium for storing and sharing photos ever since the first photograph was published on the web by Tim Berners-Lee in 1992 (an image of the CERN house band Les Horribles Cernettes). Today photo sharing sites such as Flickr, Picasa and PhotoBucket, as well as social Web sites, are used by millions of people to share their pictures.
Recent research and innovation
Research and development continues to refine the lighting, optics, sensors, processing, storage, display, and software used in digital photography. Here are a few examples.
- 3D models can be created from collections of normal images. The resulting scene can be viewed from novel viewpoints, but creating the model is very computationally intensive. An example is Microsoft's Photosynth, which provides some models of famous places as examples.
- Panoramic photographs can be created directly in camera without the need for any external processing. Some cameras feature a 3D Panorama capability, combining shots taken with a single lens from different angles to create a sense of depth.
- High dynamic range cameras and displays are commercially available. Sensors with dynamic range in excess of 1,000,000:1 are in development, and software is also available to combine multiple non-HDR images (shot with different exposures) into an HDR image.
- Motion blur can be dramatically removed by a flutter shutter (a flickering shutter that adds a signature to the blur, which postprocessing recognizes). It is not yet commercially available.
- Advanced bokeh techniques use a hardware system of 2 sensors, one to take the photo as usual while the other records depth information. Bokeh effect and refocusing can then be applied to an image after the photo is taken.
- In advanced camera or camcorders, manipulating the sensitivity of the sensor not one, but 2 or more neutral density filters are available.
- An object's specular reflection can be captured using computer-controlled lights and sensors. This is needed to create attractive images of oil paintings, for instance. It is not yet commercially available, but some museums are starting to use it.
- Dust reduction systems help keep dust off of image sensors. Originally introduced only by a few cameras like Olympus DSLRs, have now become standard in most models and brands of detachable lens camera, except the low-end/cheap ones.
Other areas of progress include improved sensors, more powerful software, advanced camera processors (sometimes using more than one processor, e.g., the Canon 7d camera has 2 Digic 4 processors), enlarged gamut displays, built in GPS & WiFi, and computer-controlled lighting.
Comparison with film photography
Advantages already in consumer level cameras
The primary advantage of consumer-level digital cameras is the low recurring cost, as users need not purchase photographic film. Processing costs may be reduced or even eliminated. Digicams tend also to be easier to carry and to use, than comparable film cameras. They more easily adapt to modern use of pictures. Some, particularly those that are smartphones, can send their pictures directly to e-mail or web pages or other electronic distribution.
Advantages of professional digital cameras
- Immediate image review and deletion is possible; lighting and composition can be assessed immediately, which ultimately conserves storage space.
- High volume of images to medium ratio; allowing for extensive photography sessions without changing film rolls. To most users a single memory card is sufficient for the lifetime of the camera whereas film rolls are a re-incurring cost of film cameras.
- Faster workflow: Management (colour and file), manipulation and printing tools are more versatile than conventional film processes. However, batch processing of RAW files can be time consuming, even on a fast computer.
- Precision and reproducibility of processing: since processing in the digital domain is purely numerical, image processing using deterministic (non-random) algorithms is perfectly reproducible and eliminates variations common with photochemical processing that make many image processing techniques difficult if not impractical.
- Digital manipulation: A digital image can be modified and manipulated much easier and faster than with traditional negative and print methods. The digital image to the right was captured in Raw image format, processed and output in 3 different ways from the source RAW file, then merged and further processed for color saturation and other special effects to produce a more dramatic result than was originally captured with the RAW image.
Manufacturers such as Nikon and Canon have promoted the adoption of digital single-lens reflex cameras (DSLRs) by photojournalists. Images captured at 2+ megapixels are deemed of sufficient quality for small images in newspaper or magazine reproduction. Eight- to 24-megapixel images, found in modern digital SLRs, when combined with high-end lenses, can approximate the detail of film prints from 35 mm film based SLRs.
Disadvantages of digital cameras
- High ISO image noise may manifest as multicolored speckles in digital images, rather than the less-objectionable "grain" of high-ISO film. While this speckling can be removed by noise-reduction software, either in-camera or on a computer, this can have a detrimental effect on image quality as fine detail may be lost in the process.
- As with any sampled signal, the combination of regular (periodic) pixel structure of common electronic image sensors and regular (periodic) structure of (typically man-made) objects being photographed can cause objectionable aliasing artefacts, such as false colors when using cameras using a Bayer pattern sensor. Aliasing is also present in film, but typically manifests itself in less obvious ways (such as increased granularity) due to the stochastic grain structure (stochastic sampling) of film.
For many consumers, the advantages of digital cameras outweigh the disadvantages. Some professional photographers still prefer film. Concerns that have been raised by professional photographers include: editing and post-processing of RAW files can take longer than 35mm film, downloading a large number of images to a computer can be time-consuming, shooting in remote sites requires the photographer to carry a number of batteries, equipment failure--while all cameras may fail, some film camera problems (e.g., meter or rangefinder problems, failure of only some shutter speeds) can be worked around. As time passes, it is expected that more professional photographers will switch to digital.
Equivalent features
Noise in a digital camera's image may sometimes be visually similar to film grain in a film camera.
Turn of the century digital cameras had a long start-up delay compared to film cameras, i.e., the delay from when they are turned on until they are ready to take the first shot, but this is no longer the case for modern digital cameras with start-up times under 1/4 seconds.
While some film cameras could reach up to 10 fps, like the Canon EOS-1V HS, professional digital SLR cameras can take still photographs at highest frame rates. While the Sony SLT technology allows rates of up to 12 fps, the Canon EOS-1Dx can take stills at a 14 fps rate. The Nikon F5 is limited to 36 continuous frames (the length of the film) while the Canon EOS-1D Mark III is able to take about 110 high definition JPEG images before its buffer must be cleared and the remaining space on the storage media can be used.
Depending on the materials and how they are stored, analog photographic film and prints may fade as they age. Similarly, the media on which digital images are stored or printed can decay or become corrupt, leading to a loss of image integrity.
Colour reproduction (gamut) is dependent on the type and quality of film or sensor used and the quality of the optical system and film processing. Different films and sensors have different color sensitivity; the photographer needs to understand his equipment, the light conditions, and the media used to ensure accurate colour reproduction. Many digital cameras offer RAW format (sensor data), which makes it possible to choose color space in the development stage regardless of camera settings.
Even in RAW format, however, the sensor and the camera's dynamics can only capture colors within the gamut supported by the hardware. When that image is transferred for reproduction on any device, the best possible gamut is the gamut that the end device supports. For a monitor, it is the gamut of the display device. For a photographic print, it is the gamut of the device that prints the image on a specific type of paper. Color gamut or Color space is an abstract term that describes an area where points of color fit in a three-dimensional space.
Professional photographers often use specially designed and calibrated monitors that help them to reproduce color accurately and consistently.
Frame aspect ratios
Most digital point & shoot cameras have an aspect ratio of 1.33 (4:3), the same as analog television or early movies. However, a 35 mm picture's aspect ratio is 1.5 (3:2). Several digital cameras take photos in either ratio, and nearly all digital SLRs take pictures in a 3:2 ratio, as most can use lenses designed for 35 mm film. Some photo labs print photos on 4:3 ratio paper, as well as the existing 3:2. In 2005 Panasonic launched the first consumer camera with a native aspect ratio of 16:9, matching HDTV. This is similar to a 7:4 aspect ratio, which was a common size for APS film. Different aspect ratios is one of the reasons consumers have issues when cropping photos. An aspect ratio of 4:3 translates to a size of 4.5"x6.0". This loses half an inch when printing on the "standard" size of 4"x6", an aspect ratio of 3:2. Similar cropping occurs when printing on other sizes, i.e., 5"x7", 8"x10", or 11"x14".
Source of the article : Wikipedia
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