یک دستگاه الکترونیکی است که برای گرفتن عکس و ذخیرهٔ آن بجای فیلم عکاسی از حسگرهای حساس به نور معمولا از نوع CCD یا CMOS استفاده میکند و تصویر گرفته شده توسط سنسور طی چند مرحله به حافظهٔ دوربین برای استفاده فرستاده میشود.
از لحاظ عملکرد کلی، دوربینهای دیجیتال بسیار شبیه به دوربینهای عکاسی دارای فیلم یا غیر دیجیتال میباشند. این دوربینها همانند دوربینهای معمولی دارای یک منظره یاب، لنز برای کانونی کردن تصویر بر روی یک وسیله حساس به نور، وسیلهای برای نگهداری و انتقال چند تصویر گرفته شده در دوربین و یک جعبه در بر گیرنده تمام این تجهیزات میباشد. در یک دوربین معمولی فیلم حساس به نور تصویر را ذخیره میسازد و بعد از عملیات شیمیایی برای نگهداری تصویر از آن استفاده میشود. در حالی که در دوربین دیجیتال این کار با استفاده از ترکیبی از فناوری پیشرفته سنسور (حسگر) تصویر و ذخیره در حافظه انجام میگیرد و اجازه میدهد که تصاویر در شکل دیجیتال ذخیره شوند و به سرعت بدون نیاز به عملیات خاصی (نظیر عملیات شیمیایی بر روی فیلم) در دسترس باشند.
گرچه اصول کلی این دوربینها شبیه به دوربینهای فیلمی هستند، نحوه کار داخل این دوربینها کاملاً متفاوت است. در این دوربینها تصویر توسط یک سنسور CCD یا یک CMOS گرفته میشود. CCD بصورت ردیفها و ستونهایی از سنسورهای نقطهای نور هستند که هر چه تعداد این نقاط بیشتر و فشرده تر باشد، تصویر دارای دقت بالاتری است) هر سنسور نور را به ولتاژی متناسب با درخشندگی نور تبدیل کرده و آن را به بخش تبدیل سیگنالهای آنالوگ به دیجیتال ADC میفرستد که در آنجا نوسانات دریافتی از CCD به کدهای مجزای باینری (عددهای مبنای دو بصورت صفر و یک) تبدیل میشود. خروجی دیجیتال از ADC به یک پردازنده سیگنالهای دیجیتال DSP فرستاده میشود که کنتراست و جزئیات تصویر در آن تنظیم میشود و قبل از فرستادن تصویر به حافظه برای ذخیره تصویر، اطلاعات را به یک فایل فشرده تبدیل میکند. هر چه نور درخشندهتر باشد، ولتاژ بالاتری تولید شده و در نتیجه پیکسلهای رایانهای روشنتری ایجاد میشود. هر چه تعداد این سنسورها که بهصورت نقطه هستند بیشتر باشد، وضوح تصویر به دست آمده بیشتر است و جزئیات بیشتری از تصویر گرفته میشود.
تمام این پروسه، پروسهای هماهنگ با محیط زیست است. سنسورهای CCD یا CMOS در تمام مدت عمر دوربین در جای خود ثابت بوده و بدون نیاز به تعویض کار میکنند. ضمناً به علت عدم وجود قطعات متحرک عمر دوربین بسیار بیشتر میشود. سنسور CCD از میلیون ها سنسور نوری تشکیل شده است و حساسیت به نور آن از سنسورهای CMOS بهتر است . در عوض در سنسور CMOS مصرف انرژی کمتر بوده و مشکل Over Expouser کمتر بوجود می آید . دوربینهای دیجیتال در بطن کار، از دوربین های آنالوگ پیروی می کنند، با این تفاوت که در این دوربین ها، همان طور که از اسمشان نیز برداشت می شود، کنترل بخش های مختلف از جمله فوکوسر و ... به صورت دیجیتالی انجام شده و یا در صفحه حساس این دوربین ها، سی سی دی و سی ماس، جایگزین فیلم های قدیمی شده است.
دریافت و ثبت تصویر در دوربین های دیجیتال [ویرایش]
صفحه های حساس در دوربین های دیجیتال حرفه ای، ccd یا cmos است که مختصراً به بررسی آن می پردازیم. حسگرهای نوری از هزاران ردیف المان نیمههادی بسیار کوچک و حساس به نور تشکیل شدهاند که میتوانند ذرات یا فوتونهای نور را به بار الکتریکی تبدیل کنند. حال هر چه شدت نور ورودی بیشتر یا کمتر باشد، الکتریسیته ایجاد شده متعاقباً دست خوش تغییر می شود. جنس این صفحه ها اغلب از عناصری از جمله سیلیسیم و ژرمانیوم است. به طور نمونه شرکت کانن در دوربین های SLR خود تاکنون تنها از سنسورهای CMOS استفاده کرده است، در حالی که شرکت نیکون از هر دو نوع سنسور بهره میگیرد. بطور کلی تفاوت کیفی زیادی بین این دو نوع سنسور وجود ندارد اما حسگرهای CMOS کم مصرف تر بوده و در شرایط کم نور و با نوردهی های طولانی عملکرد بهتری دارند . ضمناً از نظر فنی نمی توان امکان تولید سنسورهای CCD در ابعاد فول فریم (۲۴×۳۶میلیمتر ) موجود نیست.
مزیتهای دوربینهای دیجیتال [ویرایش]
مخابره: شاید مهمترین و اصلی ترین دلیل تولید دوربین دیجیتال را بتوان مخابره نامید چرا که تولید آن پس از درخواست موسسات تحقیقات فضایی از تولید کنندگان تجهیزات عکاسی برای تصویری قابل مخابره جهت تحقیقات فضایی شکل گرفت
هزینهٔ کمتر: به لحاظ اینکه در هر دوره عکاسی دیگر احتیاج به خرید، ظهور و چاپ فیلم نیست.
مقدار خطای کمتر: به علت پیش نمایش بهتر عکس و نشان دادن عکس در همان زمان میتوان در صورت مشاهدهٔ خطایی فاحش عکس را مجدادا ثبت کرد در صورتی که در عکاسی آنالوگ پس از مرحلهٔ ظهور میتوان چنین تشخیصی داد که معمولا دیر است
مقدار ریسک پایین: از بین رفتن یا افت کیفیت شدید فیلم به علت زمان، حرارت، و نور دیدگی، خطای ظهور، چاپ، تاریخ فیلم و... طبیعتا حذف شده و جای خود را از لحاظ ریسک تنها به خطاهای الکترونیکی بسیار ناچیز میدهد.
نگهداری بهتر: امکان آرشیو میلیونها عکس در یک فضای بسیار کم با ماندگاری بسیار طولانی تر
عکسبرداری متوالی:در دوربینهای آنالوگ به طور معمول بیشترین تعداد عکس برداری متوالی بیشتر از ۳۶ عدد (به لحاظ تعداد کاست) نمیشد به غیر از مواردی خاص که گاهی تا ۳۶۰ عدد اضافه میشد (با حجمی مزاحم) ولی با زحمتی چندین برابر برای تعویض فیلم! در صورتی که در دوربینهای جدید دیجیتال با فشار دادن دکمه شاتر میتوان بیش از هزاران عکس را بدون توقف در یک کارت حافظه بسیار کوچک جا داد.
A digital camera (or digicam) is a camera that takes video or still photographs by recording images on an electronic image sensor. Most cameras sold today are digital, and digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles.
Digital and film cameras share an optical system, 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. However, unlike film cameras, digital cameras can display images on a screen immediately after being recorded, and store and delete images from memory. Many digital cameras can also record moving video with sound. Some digital cameras can crop and stitch pictures and perform other elementary image editing.
Steven Sasson as an engineer at Eastman Kodak invented and built the first electronic camera using a charge-coupled device image sensor in 1975. Earlier ones used a camera tube; later ones digitized the signal. Early uses were mainly military and scientific; later medical and news applications became prominent, and in the 1990s digital cameras became a mainstream consumer product.
Image sensors 
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. The sensor is made up of millions of "buckets" that essentially count the number of photons that strike the sensor. 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 and lens quality.
Since only a few aspect ratios are commonplace (mainly 4:3 and 3:2), the number of sensor sizes in use is limited. Furthermore, sensor manufacturers do not produce every possible sensor size, but take incremental steps in sizes. For example, in 2012 the three largest sensors (in terms of pixel count) used by Canon were the 22.3, 21.1, and 17.9 megapixel CMOS sensors.
Demanding high quality and resolution (e.g. for use in professional photography), this count is an object of manufacturer competition. The highest resolution available on the market for consumer digital cameras is 80.1 MP.
Methods of image capture 
Since the first digital backs were introduced, there have been three main methods of capturing the image, each based on the hardware configuration of the sensor and color filters.
The first method is often called 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 additive colors red, green, and blue) which are exposed to the same image via a beam splitter.
The second method is referred to as multi-shot because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique. The most common originally was to use a single image sensor with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method is called 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. A third version combined the two methods without a Bayer filter on the chip.
The third method is called scanning because the sensor moves across the focal plane much like the sensor of a desktop scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. In some cases, scanning is accomplished by moving the sensor e.g. when using color co-site sampling or rotate the whole camera; a digital rotating line camera offers images of very high total resolution.
The choice of method for a given capture is determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject that moves with anything but a single-shot system. However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scanning backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.
Dramatic improvements in single-shot cameras and raw image file processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.
Filter mosaics, interpolation, and aliasing 
Most current consumer digital cameras use a Bayer filter mosaic in combination with an optical anti-aliasing filter to reduce the aliasing due to the reduced sampling of the different primary-color images. A demosaicing algorithm is used to interpolate color information to create a full array of RGB image data.
Firmware in the camera, or a software in a raw converter program such as Adobe Camera Raw, interprets the raw data from the sensor to obtain a full color image, because the RGB color model requires three intensity values for each pixel: one each for the red, green, and blue (other color models, when used, also require three or more values per pixel). A single sensor element cannot simultaneously record these three intensities, and so a color filter array (CFA) must be used to selectively filter a particular color for each pixel.
The Bayer filter pattern is a repeating 2×2 mosaic pattern of light filters, with green ones at opposite corners and red and blue in the other two positions. The high proportion of green takes advantage of properties of the human visual system, which determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation. Sometimes a 4-color filter pattern is used, often involving two different hues of green. This provides potentially more accurate color, but requires a slightly more complicated interpolation process.
The color intensity values not captured for each pixel can be interpolated (or guessed) from the values of adjacent pixels which represent the color being calculated.
Sensor size and angle of view 
Cameras with digital image sensors that are smaller than the typical 35mm film size have a smaller field or angle of view when used with a lens of the same focal length. This is because angle of view is a function of both focal length and the sensor or film size used.
If a sensor smaller than the full-frame 35mm film format is used, as in most digicams, then the field of view is cropped by the sensor to smaller than the 35mm full-frame format's field of view. This narrowing of the field of view is often described in terms of a focal length multiplier or crop factor, a factor by which a longer focal length lens would be needed to get the same field of view on a full-frame camera.
The result is geometrically similar to taking the image from the film camera and cutting it down (cropping) to the size of the sensor, ignoring various questions such as resolution. For moderately large DSLRs the crop factor may be in the range of 1.3-2 while smaller cameras use smaller sensors with a larger crop factor.
If the digital sensor has a higher or lower density of pixels per unit area than the film equivalent, then the amount of information captured differs correspondingly. While resolution can be estimated in pixels per unit area, the comparison is complex since most types of digital sensor record only a single colour at each pixel location, and different types of film have different effective resolutions. There are various trade-offs involved, since larger sensors are more expensive to manufacture and require larger lenses, while sensors with higher numbers of pixels per unit area are likely to suffer higher noise levels.
For these reasons, it is possible to obtain cheap digital cameras with sensor sizes much smaller than 35mm film, but with high pixel counts, that can still produce high-resolution images. Such cameras are usually supplied with lenses that would be classed as extremely wide angle on a 35mm camera, and that can also be smaller size and less expensive, since there is a smaller sensor to illuminate. For example, a camera with a 1/1.8" sensor has a 5.0x field of view crop, and so a hypothetical 5-50mm zoom lens produces images that look similar (again the differences mentioned above are important) to those produced by a 35mm film camera with a 25–250mm lens, while being much more compact than such a lens for a 35mm camera since the imaging circle is much smaller.
This can be useful if extra telephoto reach is desired, as a certain lens on an APS sensor produces an image equivalent to a significantly longer lens on a 35mm film camera shot at the same distance from the subject, the equivalent length of which depends on the camera's field of view crop. This is sometimes referred to as the focal length multiplier, but the focal length is a physical attribute of the lens and not the camera system itself. The disadvantage of this is that wide angle photography is made somewhat more difficult, as the smaller sensor effectively and undesirably reduces the captured field of view. Some methods of compensating for this or otherwise producing much wider digital photographs involve using a fisheye lens and "defishing" the image in post processing to simulate a rectilinear wide angle lens.
Full-frame digital SLRs, that is, those with sensor size matching a frame of 35mm film, include Canon 1D X, 1Ds and 5D series, and 6D; Kodak Pro DCS-14n; Nikon D3, D4, D600, D700 and D800 lines; and Contax N Digital. There are very few digital cameras with sensors that can approach the resolution of larger-format film cameras, with the possible exception of the Mamiya ZD (22MP), the Hasselblad H3D series of DSLRs (22 to 39 MP), and the Nikon D800 (36 MP).
Common values for field of view crop in DSLRs include 1.3x for some Canon (APS-H) sensors, 1.5x for Sony APS-C sensors used by Nikon, Pentax and Konica Minolta and for Fujifilm sensors, 1.6 (APS-C) for most Canon sensors, ~1.7x for Sigma's Foveon sensors and 2x for Kodak and Panasonic 4/3" sensors currently used by Olympus and Panasonic. Crop factors for non-SLR consumer compact and bridge cameras are larger, frequently 4x or more.
Types of digital cameras 
Digital cameras are made in a wide range of sizes, prices and capabilities. The majority are camera phones, operated as a mobile application through the cellphone menu. Professional photographers and many amateurs use larger, more expensive digital single-lens reflex cameras (DSLR) for their greater versatility. Between these extremes lie digital compact cameras and bridge digital cameras that "bridge" the gap between amateur and professional cameras. Specialized cameras including multispectral imaging equipment and astrographs continue to serve the scientific, military, medical and other special purposes for which digital photography was invented.
Compact digital cameras 
Compact cameras are designed to be tiny and portable and are particularly suitable for casual and "snapshot" uses. Hence, they are also called point-and-shoot cameras. The smallest, generally less than 20 mm thick, are described as subcompacts or "ultra-compacts" and some are nearly credit card size.
Most, apart from ruggedized or water-resistant models, incorporate a retractable lens assembly allowing a thin camera to have a moderately long focal length and thus fully exploit an image sensor larger than that on a camera phone, and a mechanized lens cap to cover the lens when retracted. The retracted and capped lens is protected from keys, coins and other hard objects, thus making it a thin, pocketable package. Subcompacts commonly have one lug and a short wrist strap which aids extraction from a pocket, while thicker compacts may have two lugs for attaching a neck strap.
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. Live preview is almost always used to frame the photo. Most have limited motion picture capability. Compacts often have macro capability and zoom lenses but the zoom range is usually less than for bridge and DSLR cameras. Generally a contrast-detect autofocus system, using the image data from the live preview feed of the main imager, focuses the lens.
For low cost and small size, these cameras typically use image sensor formats with a diagonal between 6 and 11 mm, corresponding to a crop factor between 7 and 4. This gives them weaker low-light performance, greater depth of field, generally closer focusing ability, and smaller components than cameras using larger sensors. Some cameras use larger sensor including, at the high end, a full-frame sensor.
Bridge cameras 
Bridge are higher-end digital cameras that physically and ergonomically resemble DSLRs and share with them some advanced features, but share with compacts the use of a fixed lens and a small sensor. Like compacts, most use live preview to frame the image. Their autofocus uses the same contrast-detect mechanism, but many bridge cameras have a manual focus mode, in some cases using a separate focus ring, for greater control. They originally "bridged" the gap between affordable point-and-shoot cameras and the then unaffordable earlier DSLRs.
Due to the combination of big physical size but a small sensor, many of these cameras have very highly specified lenses with large zoom range and fast aperture, partially compensating for the inability to change lenses. On some, the lens qualifies as superzoom. To compensate for the lesser sensitivity of their small sensors, these cameras almost always include an image stabilization system to enable longer handheld exposures.
These cameras are sometimes marketed as and confused with digital SLR cameras since the appearance is similar. Bridge cameras lack the reflex viewing system of DSLRs, are usually fitted with fixed (non-interchangeable) lenses (although some have a lens thread to attach accessory wide-angle or telephoto converters), and can usually take movies with sound. The scene is composed by viewing either the liquid crystal display or the electronic viewfinder (EVF). Most have a longer shutter lag than a true DSLR, but they are capable of good image quality (with sufficient light) while being more compact and lighter than DSLRs. High-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of these cameras can store images in a raw image format, or processed and JPEG compressed, or both. The majority have a built-in flash similar to those found in DSLRs.
In bright sun, the quality difference between a good compact camera and a digital SLR is minimal but bridge cameras are more portable, cost less and have a similar zoom ability to DSLR. Thus a bridge camera may better suit outdoor daytime activities, except when seeking professional-quality photos.
In low light conditions and/or at ISO equivalents above 800, most bridge cameras (or megazooms) lack in image quality when compared to even entry level DSLRs. However, their larger depth of field due to small size is usually an advantage in snapshots and sometimes in more studied work.
Mirrorless interchangeable-lens camera 
In late 2008, a new type of camera emerged, combining the larger sensors and interchangeable lenses of DSLRs with the live-preview viewing system of compact cameras, either through an electronic viewfinder or on the rear LCD. These are simpler and more compact than DSLRs due to the removal of the mirror box, and typically emulate the handling and ergonomics of either DSLRs or compacts. The system is used by Micro Four Thirds, borrowing components from the Four Thirds DSLR system. Some MILCs use a larger APS-C sensor, such as the Sony NEX series, Pentax K-01, and Canon EOS M.
Digital single lens reflex cameras 
Digital single-lens reflex cameras (DSLRs) are digital cameras based on film single-lens reflex cameras (SLRs). They take their name from their unique viewing system, in which a mirror reflects light from the lens through a separate optical viewfinder. At the moment of exposure the mirror flips out of the way, making a distinctive "clack" sound and 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. Most 21st-century DSLRs also have a "live view" mode that emulates the live preview system of compact cameras, when selected.
These cameras have much larger sensors than the other types, typically 18 mm to 36 mm on the diagonal (crop factor 2, 1.6, or 1). This gives them superior low-light performance, less depth of field at a given aperture, and a larger size.
They make use of interchangeable lenses; each major DSLR manufacturer also sells a line of lenses specifically intended to be used on their cameras. This allows the user to select a lens designed for the application at hand: wide-angle, telephoto, low-light, etc. So each lens does not require its own shutter, DSLRs use a focal-plane shutter in front of the imager, behind the mirror.
Digital rangefinders 
A rangefinder is a user-operated optical mechanism to measure subject distance once widely used on film cameras. Most digital cameras measure subject distance automatically using electro-optical techniques, but it is not customary to say that they have a rangefinder.
Line-scan camera systems 
A line-scan camera has a single row of pixel sensors, instead of a matrix of them. The frames are continuously fed to a computer that joins them to each other and makes an image. This makes possible sharp pictures of objects that have passed the camera at high speed. Sporting races commonly use this kind of camera to make photo finishes, i.e. determine the winner when multiple competitors cross the finishing line at nearly the same time. These cameras can also be used as industrial instruments for analyzing fast processes.
Many devices include digital cameras built into or integrated into them. For example, mobile phones often include digital cameras; those that do are known as camera phones. Other small electronic devices (especially those used for communication) such as PDAs, laptops and BlackBerry devices often contain an integral digital camera, and most 21st-century camcorders can also make still pictures.
Due to the limited storage capacity and general emphasis on convenience rather than image quality, almost all these integrated or converged devices store images in the lossy but compact JPEG file format.
Mobile phones incorporating digital cameras were introduced in Japan in 2001 by J-Phone. In 2003 camera phones outsold stand-alone digital cameras, and in 2006 they outsold all film-based cameras and digital cameras combined. These camera phones reached a billion devices sold in only five years, and by 2007 more than half of the installed base of all mobile phones were camera phones. Sales of separate cameras peaked in 2008.
Integrated cameras tend to be the low end of the scale of digital cameras in technical specifications, such as resolution, optical quality, and ability to use accessories. With rapid development, however, a typical year brings new high-end camera phones with capabilities similar to the low end of separate subcompacts of yesteryear.
Waterproof digital cameras include those that can be totally submerged for underwater photography and those designed to operate in wet conditions on land. Many waterproof digital cameras are shockproof and resistant to low temperatures. Waterproof housings are available to protect non-waterproof cameras in wet or submerged conditions.
21st century trend 
In 2012 compact camera sales are declining as ever-present smartphone cameras, with integrated photo sharing become more capable. DSLR-like Bridge Cameras continue to sell, having a superzoom capability that camera phones lack. DSLRs lose ground to Mirrorless interchangeable-lens camera (MILC)s offering the same sensor size in a smaller camera. A few expensive ones use a full frame sensor as DSLR professional cameras.
Transferring photos 
Many digital cameras can connect directly to a computer to transfer data:
A common alternative is the use of a card reader which may be capable of reading several types of storage media, as well as high speed transfer of data to the computer. Use of a card reader also avoids draining the camera battery during the download process. An external card reader allows convenient direct access to the images on a collection of storage media. But if only one storage card is in use, moving it back and forth between the camera and the reader can be inconvenient. Many computers have a card reader built in, at least for SD cards.
Printing photos 
Wireless connectivity can also provide for printing photos without a cable connection.
Polaroid has introduced a printer integrated into its digital camera which creates a small, printed copy of a photo. This is reminiscent of the original instant camera, popularized by Polaroid in 1975.
Displaying photos 
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.
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.
Many digital cameras have preset modes for different applications. Within the constraints of correct exposure various parameters can be changed, including exposure, aperture, focusing, light metering, white balance, and equivalent sensitivity. For example a portrait might use a wider aperture to render the background out of focus, and would seek out and focus on a human face rather than other image content.
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 and the other formats are rare. In January 2012, a faster XQD card format was announced.
Digital cameras have computers inside, hence have internal memory, and many cameras can use some of this internal memory for a limited capacity for pictures that can be transferred to or from the card or through the camera's connections.
Most manufacturers of digital cameras do not provide drivers and software to allow their cameras to work with Linux or other free software. Still, many cameras use the standard USB storage protocol, and are thus easily usable. Other cameras are supported by the gPhoto project.
File formats 
The Joint Photography Experts Group standard (JPEG) is the most common file format for storing image data. Other file types include Tagged Image File Format (TIFF) and various Raw image formats.
Many cameras, especially high-end ones, support a raw image format. A raw image is the unprocessed set of pixel data directly from the camera's sensor, often saved in a proprietary format. Adobe Systems has released the DNG format, a royalty-free raw image format used by at least 10 camera manufacturers.
Raw files initially had to be processed in specialized image editing programs, but over time many mainstream editing programs, such as Google's Picasa, have added support for raw images. Rendering to standard images from raw sensor data allows more flexibility in making major adjustments without losing image quality or retaking the picture.
Formats for movies are AVI, DV, MPEG, MOV (often containing motion JPEG), WMV, and ASF (basically the same as WMV). Recent formats include MP4, which is based on the QuickTime format and uses newer compression algorithms to allow longer recording times in the same space.
Other formats that are used in cameras but not for pictures are the Design Rule for Camera Format (DCF), an ISO specification for the camera's internal file structure and naming, and Digital Print Order Format (DPOF), which dictates what order images are to be printed in and how many copies.
Digital cameras have high power requirements, and over time have become smaller, resulting in an ongoing need to develop a battery small enough to fit in the camera and yet able to power it for a reasonable length of time.
Two broad types of batteries are in use for digital cameras.
Off-the-shelf batteries may be single-use disposable or reusable rechargeable batteries. In either case they conform to an established off-the-shelf form factor, most commonly AA, CR2, or CR-V3 batteries, with AAA batteries in a handful of cameras. The CR2 and CR-V3 batteries are lithium based, and intended for single use. They are also commonly seen in camcorders. AA batteries are the most common; however, the non-rechargeable alkaline batteries supplied with low-end cameras are capable of powering most cameras for only a very short time. They may serve satisfactorily in cameras that are only occasionally used.
Consumers with more than an occasional need use AA Nickel metal hydride batteries (NiMH) instead, which provide adequate energy and are rechargeable. NIMH batteries do not provide as much energy per volume as lithium ion batteries, and they also tend to discharge when not used. For the same energy, a NiMH rechargeable battery takes up to twice the volume of a Li-on rechargeable battery, and is three to five times heavier, but only costs half as much. Rechargeable batteries are available in various ampere-hour (Ah) or milli-ampere-hour (mAh) ratings, which are approximately proportional to shots per charge.
Typically mid-range consumer models and some low end cameras use off-the-shelf batteries; only a very few DSLR cameras accept them (for example, Sigma SD10, or some Pentax DSLRs via an optional adapter). However, most battery grips for DSLRs come with a separate holder to accommodate AA cells. Rechargeable RCR-V3 lithium-ion batteries are also available as an alternative to non-rechargeable CR-V3 batteries. Cameras, especially earlier ones made for AA-size batteries assumed that these would be of the non-rechargeable, preferably alkaline manganese type delivering 1.5 volts per cell. Rechargeable NiCd or NiMH cells only deliver 1.2 volts, which means that many such cameras will only operate for a short time or not at all even with new and newly charged 1.2 volt units. A portable ultra-high-endurance external power-supply for the shoulder bag to operate older 6 volt cameras can be made up of five 1.2 volt C-size cells which can be either NiCd or NiMH, with a cable and 4mm DC-plug.
The second type of battery for digital cameras is proprietary battery formats. These are built to a manufacturer's custom specifications, and can be either aftermarket replacement parts or OEM. Almost all proprietary batteries are lithium ion. While they only accept a certain number of recharges before the battery life begins degrading (typically up to 500 cycles), they provide considerable performance for their size. A result is that at the two ends of the spectrum both high end professional cameras and low end consumer models tend to use lithium ion batteries.
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 most 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 Kodak DCS series, were developed from 35 mm film cameras. The technology of the time, however, meant that rather than being digital "backs" the bodies of these cameras were mounted on large, bulky digital units, often bigger than the camera portion itself. These were factory built cameras, however, not aftermarket conversions.
A few 35 mm cameras have had digital camera 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 a low unit production, and typical digital backs for them cost 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. For example Phase One's P45 39 MP image back creates a single TIFF image of size up to 224.6 MB, and even greater pixel counts are available. Medium format digitals such as this 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. (Canon EOS-1D Mark IV and Nikon D3S have ISO 12800 plus Hi-3 ISO 102400 with the Canon EOS-1Dx's ISO of 204800)
Digital camera backs 
In the industrial and high-end professional photography market, some camera systems use modular (removable) image sensors. For example, some medium format SLR cameras, such as the Mamiya 645D series, allow installation of either a digital camera back or a traditional photographic film back.
Linear array cameras are also called scan backs.
Most earlier digital camera backs used linear array sensors, moving vertically to digitize the image. Many of them only capture grayscale images. The relatively long expsoure times, in the range of seconds or even minutes generally limit scan backs to studio applications, where all aspects of the photographic scene are under the photographer's control.
Some other camera backs use CCD arrays similar to typical cameras. These are called single-shot backs.
Since it is much easier to manufacture a high-quality linear CCD array with only thousands of pixels than a CCD matrix with millions, very high resolution linear CCD camera backs were available much earlier than their CCD matrix counterparts. For example, you could buy an (albeit expensive) camera back with over 7,000 pixel horizontal resolution in the mid-1990s. However, as of 2004[update], it is still difficult to buy a comparable CCD matrix camera of the same resolution. Rotating line cameras, with about 10,000 color pixels in its sensor line, are able, as of 2005[update], to capture about 120,000 lines during one full 360 degree rotation, thereby creating a single digital image of 1,200 Megapixels.
Most modern digital camera backs use CCD or CMOS matrix sensors. The matrix sensor captures the entire image frame at once, instead of incrementing scanning the frame area through the prolonged exposure. For example, Phase One produces a 39 million pixel digital camera back with a 49.1 x 36.8 mm CCD in 2008. This CCD array is a little smaller than a frame of 120 film and much larger than a 35 mm frame (36 x 24 mm). In comparison, consumer digital cameras use arrays ranging from 36 x 24 mm (full frame on high end consumer DSLRs) to 7.2 x 5.3 mm (on point and shoot cameras) CMOS sensor.
Relatively few complete digital SLR cameras have sensors large enough to compete (except by image stitching) with the image detail offered by medium to large format film cameras. Phase One, Mamiya, and Hasselblad in 2011 manufacture medium format digital devices that can capture 30MP up to 80MP. These large and expensive cameras, having high build quality and few moving parts, tend to be long lasting and are prominent on the used market.