یک دستگاه الکترونیکی است که برای گرفتن عکس و ذخیرهٔ آن بجای فیلم عکاسی از حسگرهای حساس به نور معمولاً 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 معمولاً 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... طبیعتاً 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 encodes digital images and videos digitally and stores them for later reproduction. 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; followed by medical and news applications. In the mid to late 1990s digital cameras became common among consumers. By the mid-2000s digital cameras had largely replaced film cameras, and higher-end cell phones had an integrated digital camera. By the beginning of the 2010s smartphones had an integrated digital camera.
The two major types of digital image sensor are CCD and CMOS. A CCD sensor has one amplifier for all the pixels, while each pixel in a CMOS active-pixel sensor has its own amplifier. Compared to CCDs, CMOS sensors use less power. Some modern cameras use back-side-illuminated CMOS (BSI-CMOS) sensors which use light more efficiently. The final image quality is more dependent on the image processing capability of the camera.
The resolution of a digital camera is often limited by the image sensor that turns light into discrete signals. 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 demosaicing to recreate a full-color image. The number of pixels in the sensoor determines the camera's "pixel count". In a typical sensor, the pixel count is the product of the number of rows and the number of columns. For example, a 1,000 by 1,000 pixel sensor would have 1,000,000 pixels, or 1 megapixel.
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.
single-shot capture systems use either one sensor chip 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.
multi-shot exposes the sensor 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 passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method is called Microscanning. This method uses a single sensor chip with a Bayer filter and physically moved the sensor on the focus plane of the lens to construct a higher resolution image than the native resolution of the chip. 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 an image scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. Scanning may be accomplished by moving the sensor e.g. when using color co-site sampling or rotating 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.[original research?]
Improvements in single-shot cameras and image file processing at the beginning of the 21st century made single shot cameras almost completely dominant, even in high-end commercial photography.
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 2x2 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 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.
The crop factor is relative to the 35mm film format. If a smaller sensor is used, as in most digicams, 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 may be described as crop factor, a factor by which a longer focal length lens would be needed to get the same field of view on a 35mm film 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. The amount of information captured is dependent on sensor density
For example, a camera with a 1/1.8-inch sensor has a 5.0x field of view crop. When it is mated with a 5-50mm zoom lens, it produces an image with field of view similar to those produced by a 35mm film camera with a 25–250mm lens. The smaller sensor reduces the captured field of view.
Full-frame digital SLRs utilize a sensor of the same size as a frame of 35mm film. Some examples of cameras are 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.
Common values for field of view crop in DSLRs using active pixel sensors 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-inch 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 come in a wide range of sizes, prices and capabilities. In addition to general purpose digital cameras, specialized cameras including multispectral imaging equipment and astrographs are used for scientific, military, medical and other special purposes.
Compact digital cameras
Compact cameras are intended to be portable (pocketable) and are particularly suitable for casual "snapshot".
Many incorporate a retractable lens assembly that provides optical zoom. In most models, an auto actuating lens cover protects the lens from elements. Most ruggedized or water-resistant models do not retract, and most with (superzoom) capability do not retract fully. Some compact cameras have image stabilization.
Compact cameras are usually designed to be easy to use. Almost all include an automatic mode, or "auto mode", which automatically makes all camera settings for the user. It is common for current compact cameras to include more advanced features to accommodate users who desire more detailed control the camera's settings. Compact digital cameras typically contain a small sensor which trades-off 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. A few high end compact digital cameras have a hotshoe for connecting to an external flash. Live preview is almost always used to frame the photo on an integrated LCD display. In addition to being able to take still photographs almost all compact cameras have the ability to record video.
Compacts often have macro capability and zoom lenses, but the zoom range (up to 30x) is generally enough for candid photography but less than is available on bridge cameras (up to 60x), or the interchangeable lenses of DSLR cameras available at a much higher cost. Autofocus systems in compact digital cameras generally are based on a contrast-detection methodology using the image data from the live preview feed of the main imager. Some compact digital cameras use a hybrid autofocus system similar to what is commonly available on DSLRs.
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 a larger sensor including, at the high end, a pricey full-frame sensor compact camera, such as Sony Cyber-shot DSC-RX1, but have capability near that of a DSLR.
A variety of additional features are available depending on the model of the camera. Such features include ones such as GPS, compass, barometer and altimeter for above mean sea level or under(water) mean sea level. and some are rugged and waterproof.
Bridge cameras physically resemble DSLRs, and are sometimes called DSLR-shape or DSLR-like. They provide some similar features but, like compacts, they use a fixed lens and a small sensor. Some compact cameras have also PSAM mode. Most use live preview to frame the image. Their usual autofocus is by the same contrast-detect mechanism as compacts, but many bridge cameras have a manual focus mode and some have a separate focus ring for greater control.
Big physical size and small sensor allow superzoom and wide aperture. Bridgcams generally include an image stabilization system to enable longer handheld exposures, sometimes better than DSLR for low light condition.
Bridge cameras are usually fitted with fixed (non-interchangeable) lenses. Some have a lens thread to attach an accessory wide-angle or telephoto converters, but almost all bridge cameras can take photos at 24mm, 22mm or even 20mm, in 35mm equivalent terms, so practically lens thread is little used except for UV or Circular Polarizing filter and lenshood. The scene is composed by viewing the display or the electronic viewfinder (EVF). Most have a slightly longer shutter lag than a DSLR. 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, but only a few have hotshoe.
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. Thus a bridge camera may better suit outdoor daytime activities, except when seeking professional-quality photos.
Mirrorless interchangeable-lens cameras
In late 2008, a new type of camera emerged called mirrorless interchangeable-lens camera (MILC), which uses various sensors and offers lens interchangeability. These are simpler and more compact than DSLRs due to not having a lens reflex system. MILC camera models are available with various sensor sizes including: a small 1/2.3 in sensor, as is commonly used in bridge cameras such as the Pentax Q; a 1 in sensor; a micro four thirds sensor; an APS-C sensor such as the Sony NEX series, Pentax K-01, and Canon EOS M; and some, such as the Sony Alpha 7, use a full frame sensor.
Olympus and Panasonic released many micro four third system cameras with interchangeable lenses which are fully compatible each other without any adapter, while the others have proprietary mounts.[relevant? ]
Modular camera is also interchangeable, but the body of the camera has no sensor and the sensor is belong to interchangeable sensor-lens. The first of Modular camera is Ricoh GXR.
At CES 2013, Sakar International announced Polaroid iM1836 1"-18MP camera with interchangeable sensor-lens which was like Ricoh GXR done with sensor and shutter are located in the lens. An adapter for Micro Four Thirds, Nikon and K-mount lenses is planned to accommodate with the camera.
Digital single-lens reflex cameras
Digital single-lens reflex cameras (DSLR) use a mirror to direct light from the lens through a separate optical viewfinder. The mirror is moved out of the way to direct the image to the sensor at the time of exposure.
Autofocus is accomplished using sensors in the mirror box. Some DSLRs have a "live view" mode that allows framing using the screen with image from the sensor.
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 use interchangeable lenses for versatility. Some lenses are made for digital SLR use only.
Digital Single Lens Translucent (DSLT) cameras
A DSLT uses a fixed translucent mirror instead of a moving reflex mirror as in DSLR. A translucent mirror or transmissive mirror or semi-transparent mirror is a mirror which reflects the light to two things at the same time. It reflects it along the path to a pentaprism/pentamirror which then goes to an optical view finder (OVF) as is done with a reflex mirror in DSLR cameras. The translucent mirror also sends light along a second path to the sensor. The total amount of light is not changes, just some of the light travels one path and some of it travels the other. The consequences is that DSLT cameras should shoot a half stop differently from DSLR, but in practice there are no significant differences between DSLT and DSLR. One advantage of using a DSLT camera is the blind moments a DSLR user experiences while the reflecting mirror is moved to send the light to the sensor instead of the viewfinder do not exist for DSLT cameras. Because there is no time at which light is not traveling along both paths, DSLT cameras get the benefit of continuous auto-focus tracking. This is especially beneficial for burst mode shooting in low-light conditions.
Until early 2014, only Sony had released DSLT cameras. By March 2014, Sony had released more DSLTs than DSLRs with a relatively complete lenses line-up, but with very limited support from third parties lenses and very limited near-fully compatible third parties external flashes.
Line-scan camera systems
A line-scan camera traditionally has a single row of pixel sensors, instead of a matrix of them. The lines are continuously fed to a computer that joins them to each other and makes an image. This is most commonly done by connecting the camera output to a frame grabber which resides in a PCI slot of an industrial computer. The frame grabber acts to buffer the image and sometimes provide some processing before delivering to the computer software for processing.
Multiple rows of sensors may be used to make colored images, or to increase sensitivity by TDI (Time delay and integration).
Many industrial applications require a wide field of view. Traditionally maintaining consistent light over large 2D areas is quite difficult. With a line scan camera all that is necessary is to provide even illumination across the “line” currently being viewed by the camera. This makes possible sharp pictures of objects that pass the camera at high speed.
Such cameras are also commonly used to make photo finishes, to determine the winner when multiple competitors cross the finishing line at nearly the same time. They can also be used as industrial instruments for analyzing fast processes.
A rangefinder is a user-operated optical mechanism to measure subject distance. Most digital cameras measure subject distance automatically using electro-optical techniques, but it is not customary to say that they have a rangefinder.
Many devices have a built-in digital camera. For example, mobile phones, PDAs and laptop computers. Built-in cameras generally store the images in 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 film and digital stand-alone cameras. Five billion camera phones were sold in 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.
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.
Sales of traditional digital cameras have declined due to the increasing use of smartphones for casual photography, which also enable easier manipulation and sharing of photos through the use of apps and web-based services. "Bridge cameras", in contrast, have held their ground with functionality that most smartphone cameras lack, such as optical zoom and other advanced features. DSLRs have also lost 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.
In response to the convenience and flexibility of smartphone cameras, some manufacturers produced "smart" digital cameras that combine features of traditional cameras with those of a smartphone. In 2012, Nikon and Samsung released the Coolpix S800c and Galaxy Camera, the first two digital cameras to run the Android operating system. Since this software platform is used in many smartphones, they can integrate with services (such as e-mail attachments, social networks and photo sharing sites) as smartphones do, and use other Android-compatible software as well.
In an inversion, some phone makers have introduced smartphones with cameras designed to resemble traditional digital cameras. Nokia released the 808 PureView and Lumia 1020 in 2012 and 2013; the two devices respectively run the Symbian and Windows Phone operating systems, and both include a 41-megapixel camera (along with a camera grip attachment for the latter). Similarly, Samsung introduced the Galaxy S4 Zoom, having a 16-megapixel camera and 10x optical zoom, combining traits from the Galaxy S4 Mini with the Galaxy Camera.
Light-field cameras were introduced in 2013 with one consumer product and several professional ones.
After a big dip of sales in 2012, consumer digital camera sales declined again in 2013 by 36 percent. In 2011, compact digital cameras sold 10 million per month. In 2013, sales fell to about 4 million per month. DSLR and MILC sales also declined in 2013 by 10–15% after almost ten years of double digit growth. These declines are attributed to the combination of superior software being available on smartphones and that the image quality on smartphones is good enough for most consumers.
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.
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 1972.
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 stand alone digital cameras store image data in flash memory cards or other removable media. Most separate cameras use SD format, while a few use CompactFlash or other types. In January 2012, a faster XQD card format was announced. In early 2014, some high end cameras have two hot-swapable memory slots. Photographers can swap one of the memory card with camera-on. Each memory slot can accept either Compact Flash or SD Card. All new Sony cameras also have two memory slots, one for its Memory Stick and one for SD Card, but not hot-swapable.
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.
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 become smaller over time, 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.
Digital cameras utilize either proprietary or standard consumer batteries. As of March 2014[update], most cameras use proprietary lithium-ion batteries while some use standard AA batteries or primarily use a proprietary Lithium-ion rechargeable battery pack but have an optional AA battery holder available.
The most common class of battery used in digital cameras is proprietary battery formats. These are built to a manufacturer's custom specifications. Almost all proprietary batteries are lithium-ion. In addition to being available from the OEM, aftermarket replacement batteries are commonly available for most camera models.
Standard consumer batteries
Digital cameras that utilize off-the-shelf batteries are typically designed to be able to use both single-use disposable and rechargeable batteries, but not with both types in use at the same time. The most common off-the-shelf battery size used is AA. CR2, CR-V3 batteries, and AAA batteries are also used in some cameras. The CR2 and CR-V3 batteries are lithium based, intended for a single use. Rechargeable RCR-V3 lithium-ion batteries are also available as an alternative to non-rechargeable CR-V3 batteries.
Some battery grips for DSLRs come with a separate holder to accommodate AA cells as an external power source.
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 exposure 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 1.28 x 0.96 mm (on camera phones) CMOS sensor.