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Image resolution is the detail an image holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail. Image resolution can be measured in various ways. Resolution quantifies how close lines can be to each other and still be visibly ''resolved''. Resolution units can be tied to physical sizes (e.g. lines per mm, lines per inch), to the overall size of a picture (lines per picture height, also known simply as lines, TV lines, or TVL), or to angular subtense. Instead of single lines, line pairs are often used, composed of a dark line and an adjacent light line; for example, a resolution of 10 lines per millimeter means 5 dark lines alternating with 5 light lines, or 5 line pairs per millimeter (5 LP/mm).
Photographic lens A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capab ...
and film resolution are most often quoted in line pairs per millimeter.


Types

The resolution of digital cameras can be described in many different ways.


Pixel count

The term ''resolution'' is often considered equivalent to
pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...
count in digital imaging, though international standards in the
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices ...
field specify it should instead be called "Number of Total Pixels" in relation to image sensors, and as "Number of Recorded Pixels" for what is fully captured. Hence, CIPA DCG-001 calls for notation such as "Number of Recorded Pixels 1000 × 1500". According to the same standards, the "Number of Effective Pixels" that an
image sensor An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of c ...
or
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices ...
has is the count of
pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...
sensors that contribute to the final image (including pixels not in said image but nevertheless support the image filtering process), as opposed to the number of ''total pixels'', which includes unused or light-shielded pixels around the edges. An image of N pixels height by M pixels wide can have any resolution less than N lines per picture height, or N TV lines. But when the pixel counts are referred to as "resolution", the convention is to describe the ''pixel resolution'' with the set of two positive integer numbers, where the first number is the number of pixel columns (width) and the second is the number of pixel rows (height), for example as ''7680 × 6876''. Another popular convention is to cite resolution as the total number of pixels in the image, typically given as number of megapixels, which can be calculated by multiplying pixel columns by pixel rows and dividing by one million. Other conventions include describing pixels per length unit or pixels per area unit, such as pixels per inch or per square inch. None of these ''pixel resolutions'' are true resolutions, but they are widely referred to as such; they serve as
upper bound In mathematics, particularly in order theory, an upper bound or majorant of a subset of some preordered set is an element of that is greater than or equal to every element of . Dually, a lower bound or minorant of is defined to be an eleme ...
s on image resolution. Below is an illustration of how the same image might appear at different pixel resolutions, if the pixels were poorly rendered as sharp squares (normally, a smooth image reconstruction from pixels would be preferred, but for illustration of pixels, the sharp squares make the point better). An image that is 2048 pixels in width and 1536 pixels in height has a total of 2048×1536 = 3,145,728 pixels or 3.1 megapixels. One could refer to it as 2048 by 1536 or a 3.1-megapixel image. The image would be a very low quality image (72ppi) if printed at about 28.5 inches wide, but a very good quality (300ppi) image if printed at about 7 inches wide. The number of photodiodes in a color
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices ...
image sensor is often a multiple of the number of pixels in the image it produces, because information from an array of color image sensors is used to reconstruct the color of a single pixel. The image has to be interpolated or
demosaic A demosaicing (also de-mosaicing, demosaicking or debayering) algorithm is a digital image process used to reconstruct a full color image from the incomplete color samples output from an image sensor overlaid with a color filter array (CFA). It is ...
ed to produce all three colors for each output pixel.


Spatial resolution

The terms blurriness and sharpness are used for digital images but other descriptors are used to reference the hardware capturing and displaying the images. Spatial resolution in radiology refers to the ability of the imaging modality to differentiate two objects. Low spatial resolution techniques will be unable to differentiate between two objects that are relatively close together. The measure of how closely lines can be resolved in an image is called spatial resolution, and it depends on properties of the system creating the image, not just the pixel resolution in pixels per inch (ppi). For practical purposes the clarity of the image is decided by its spatial resolution, not the number of pixels in an image. In effect, spatial resolution refers to the number of ''independent'' pixel values per unit length. The spatial resolution of consumer displays ranges from 50 to 800 pixel lines per inch. With scanners, optical resolution is sometimes used to distinguish spatial resolution from the number of pixels per inch. In remote sensing, spatial resolution is typically limited by diffraction, as well as by aberrations, imperfect focus, and atmospheric distortion. The
ground sample distance In remote sensing, ground sample distance (GSD) in a digital photo (such as an orthophoto) of the ground from air or space is the distance between pixel centers measured on the ground. For example, in an image with a one-meter GSD, adjacent pixels i ...
(GSD) of an image, the pixel spacing on the Earth's surface, is typically considerably smaller than the resolvable spot size. In astronomy, one often measures spatial resolution in data points per arcsecond subtended at the point of observation, because the physical distance between objects in the image depends on their distance away and this varies widely with the object of interest. On the other hand, in electron microscopy, line or fringe resolution refers to the minimum separation detectable between adjacent parallel lines (e.g. between planes of atoms), whereas ''point resolution'' instead refers to the minimum separation between adjacent points that can be both detected ''and interpreted'' e.g. as adjacent columns of atoms, for instance. The former often helps one detect periodicity in specimens, whereas the latter (although more difficult to achieve) is key to visualizing how individual atoms interact. In Stereoscopic 3D images, spatial resolution could be defined as the spatial information recorded or captured by two viewpoints of a
stereo camera A stereo camera is a type of camera with two or more lenses with a separate image sensor or film frame for each lens. This allows the camera to simulate human binocular vision, and therefore gives it the ability to capture three-dimensional ...
(left and right camera).


Spectral resolution

Pixel encoding limits the information stored in a digital image, and the term color profile is used for digital images but other descriptors are used to reference the hardware capturing and displaying the images. Spectral resolution is the ability to resolve spectral features and bands into their separate components.
Color image A digital image is an image composed of picture elements, also known as ''pixels'', each with ''finite'', '' discrete quantities'' of numeric representation for its intensity or gray level that is an output from its two-dimensional functions f ...
s distinguish light of different spectra.
Multispectral image Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by Filter (optics), filters or detected with the use of instruments that are sensitive to particu ...
s can resolve even finer differences of spectrum or
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...
by measuring and storing more than the traditional 3 of common RGB color images.


Temporal resolution

Temporal resolution (TR) refers to the precision of a measurement with respect to time.
Movie camera A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either on an image sensor or onto film stock, in order to produce a moving image to project onto a movie sc ...
s and high-speed cameras can resolve events at different points in time. The time resolution used for movies is usually 24 to 48
frames per second A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (con ...
(frames/s), whereas high-speed cameras may resolve 50 to 300 frames/s, or even more. The Heisenberg uncertainty principle describes the fundamental limit on the maximum spatial resolution of information about a particle's coordinates imposed by the measurement or existence of information regarding its momentum to any degree of precision. This fundamental limitation can, in turn, be a factor in the maximum imaging resolution at subatomic scales, as can be encountered using scanning electron microscopes.


Radiometric resolution

Radiometric resolution determines how finely a system can represent or distinguish differences of intensity, and is usually expressed as a number of levels or a number of
bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...
s, for example 8 bits or 256 levels that is typical of computer image files. The higher the radiometric resolution, the better subtle differences of intensity or reflectivity can be represented, at least in theory. In practice, the effective radiometric resolution is typically limited by the noise level, rather than by the number of bits of representation.


Resolution in various media

This is a list of traditional, analogue horizontal resolutions for various media. The list only includes popular formats, not rare formats, and all values are approximate, because the actual quality can vary machine-to-machine or tape-to-tape. For ease-of-comparison, all values are for the NTSC system. (For PAL systems, replace 480 with 576.) Analog formats usually had less chroma resolution. * Analogue and early digital Many cameras and displays offset the color components relative to each other or mix up temporal with spatial resolution: File:Bayer matrix.svg,
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices ...
(Bayer
color filter array In digital imaging, a color filter array (CFA), or color filter mosaic (CFM), is a mosaic of tiny color filters placed over the pixel sensors of an image sensor to capture color information. The term is also used in reference to e paper devices ...
) File:Lcd display dead pixel.jpg, LCD (Triangular
pixel geometry The components of the pixels (primary colors red, green and blue) in an image sensor or display can be ordered in different patterns, called pixel geometry. The geometric arrangement of the primary colors within a pixel varies depending on usage ...
) File:Shadow mask closeup cursor.jpg, CRT (shadow mask)
* Narrowscreen 4:3 computer display resolutions ** 320×200: MCGA ** 320×240: QVGA ** 640×480: VGA ** 800×600:
Super VGA Super VGA (SVGA) is a broad term that covers a wide range of computer display standards that extended IBM's VGA specification. When used as shorthand for a resolution, as VGA and XGA often are, SVGA refers to a resolution of 800×600. History ...
** 1024×768: XGA / EVGA ** 1600x1200: UXGA * Analog ** 320×200: CRT monitors ** 352×240: Video CD ** 333×480: VHS, Video8, Umatic ** 350×480: Betamax ** 420×480: Super Betamax,
Betacam Betacam is a family of half-inch professional videocassette products developed by Sony in 1982. In colloquial use, "Betacam" singly is often used to refer to a Betacam camcorder, a Betacam tape, a Betacam video recorder or the format itself. Al ...
** 460×480: Betacam SP, Umatic SP, NTSC (Over-The-Air TV) ** 580×480: Super VHS, Hi8, LaserDisc ** 700×480: Enhanced Definition Betamax, Analog broadcast limit (
NTSC The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
) ** 768×576: Analog broadcast limit (
PAL Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...
, SECAM) * Digital ** 500×480: Digital8 ** 720×480: D-VHS,
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...
, miniDV, Digital Betacam (NTSC) ** 720×480: Widescreen DVD (anamorphic) (NTSC) ** 854×480: EDTV (Enhanced Definition Television) ** 720×576: D-VHS,
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...
, miniDV, Digital8, Digital Betacam (PAL/SECAM) ** 720×576: Widescreen DVD (anamorphic) (PAL/SECAM) ** 1280×720: D-VHS,
HD DVD HD DVD (short for High Definition Digital Versatile Disc) is an obsolete high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the ...
,
Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc data storage format. It was invented and developed in 2005 and released on June 20, 2006 worldwide. It is designed to supersede the DVD format, and capable of st ...
, HDV (miniDV) ** 1440×1080: HDV (miniDV) ** 1920×1080: HDV (miniDV), AVCHD, HD DVD, Blu-ray, HDCAM SR ** 1998×1080: 2K Flat (1.85:1) ** 2048×1080: 2K Digital Cinema ** 3840×2160: 4K UHDTV,
Ultra HD Blu-ray Ultra HD Blu-ray (4K Ultra HD, UHD-BD, or 4K Blu-ray) is a digital optical disc data storage format that is an enhanced variant of Blu-ray. Ultra HD Blu-ray discs are incompatible with existing standard Blu-ray players, though a traditional Bl ...
** 4096×2160: 4K Digital Cinema ** 7680×4320:
8K UHDTV Ultra-high-definition television (also known as Ultra HD television, Ultra HD, UHDTV, UHD and Super Hi-Vision) today includes 4K UHD and 8K UHD, which are two digital video formats with an aspect ratio of 16:9. These were first proposed by ...
** 15360×8640: 16K Digital Cinema ** 61440×34560: 64K Digital Cinema ** Sequences from newer films are scanned at 2,000, 4,000, or even 8,000 columns, called 2K, 4K, and 8K, for quality visual-effects editing on computers. ** IMAX, including IMAX HD and OMNIMAX: approximately 10,000×7,000 (7,000 lines) resolution. It is about 70 MP, which is currently highest-resolution single-sensor digital cinema camera (as of January 2012). * Film ** 35 mm film is scanned for release on DVD at 1080 or 2000 lines as of 2005. ** The actual resolution of 35 mm
original camera negative The original camera negative (OCN) is the film in a traditional film-based movie camera which captures the original image. This is the film from which all other copies will be made. It is known as raw stock prior to exposure. The size of a roll v ...
s is the subject of much debate. Measured resolutions of negative film have ranged from 25–200 LP/mm, which equates to a range of 325 lines for 2-perf, to (theoretically) over 2300 lines for
4-perf Negative pulldown is the manner in which an image is exposed on a film stock, described in the number of film perforations spanned by an individual frame. It can also describe the orientation of the image on the negative, whether it is captured ho ...
shot on T-Max 100. Kodak states that 35 mm film has the equivalent of 6K resolution horizontally according to a Senior Vice President of IMAX. * Print * Modern digital camera resolutions ** Digital medium format camera – single, not combined one large digital sensor – 80 MP (starting from 2011, current as of 2013) – 10320 × 7752 or 10380 × 7816 (81.1 MP). ** Mobile phone –
Nokia 808 PureView The Nokia 808 PureView is a Symbian-powered smartphone first unveiled on 27 February 2012 at the Mobile World Congress. It is the first smartphone to feature Nokia's PureView Pro technology, a pixel oversampling technique that reduces an im ...
– 41 MP (7728 × 5368), Nokia Lumia 1020 – also 41 MP (7712 × 5360) ** Digital still camera – Canon EOS 5DS – 51 MP (8688 × 5792)


See also

* Display resolution *
Dots per inch Dots per inch (DPI, or dpiThe acronym appears in sources as either "DPI" or lowercase "dpi". See "Print Resolution Understanding 4-bit depth – Xerox" (PDF). Xerox.com. September 2012.) is a measure of spatial printing, video or image scanner ...
* Multi-exposure HDR capture *
Image scaling In computer graphics and digital imaging, image scaling refers to the resizing of a digital image. In video technology, the magnification of digital material is known as upscaling or resolution enhancement. When scaling a vector graphic image ...
* Image scanner *
Kell factor The Kell factor, named after RCA engineer Raymond D. Kell, is a parameter used to limit the bandwidth of a sampled image signal to avoid the appearance of beat frequency patterns when displaying the image in a discrete display device, usually ...
, which typically limits the number of visible lines to 0.7x of the device resolution * Pixel density


References

{{Reflist Computer graphics Image processing