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Image resolution describes the detail an image holds. An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually The term applies equally to digital images, film images, and other types of images. A digital image is a representation of a two-dimensional Image using ones and zeros (binary Higher resolution means more image detail.

Image resolution can be measured in various ways. Basically, resolution quantifies how close lines can be to each other and still be visibly resolved. VisiCorp 's VisiOn was a short-lived but influential Graphical user interface -based Operating environment program for IBM PC compatible Resolution units can be tied to physical sizes (e. g. lines per mm, lines per inch) or to the overall size of a picture (lines per picture height, also known simply as lines, or TV lines). Furthermore, line pairs are often used instead of lines. A line pair is a pair of adjacent dark and light lines, while lines counts both dark lines and light lines. A resolution of 10 lines per millimeter means 5 dark lines alternating with 5 light lines, or 5 line pairs per millimeter. Photographic lens and film resolution are most often quoted in line pairs per millimeter. A photographic lens (also known as objective lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with

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Resolution of digital images

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

Pixel resolution

The term resolution is often used as a pixel count in digital imaging, even though American, Japanese, and international standards specify that it should not be so used, at least in the digital camera field. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Many compact digital still cameras can record Sound and moving Video as well as still Photograph. An image of N pixels high 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 640 by 480. The integers (from the Latin integer, literally "untouched" hence "whole" the word entire comes from the same origin but via French 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. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image 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 bounds on image resolution. In Mathematics, especially in Order theory, an upper bound of a Subset S of some Partially ordered set ( P, &le . . . . . . . . . . . . .

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).

Image:Resolution illustration.png

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. As the megapixels of a camera increase so does the ability of a camera to produce a larger image; a 5 megapixel camera is capable of capturing a larger image than a 3 megapixel camera.

Larger monitor screens usually have higher screen resolution, measured in pixels.

Spatial resolution

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 computer monitors is generally 72 to 100 lines per inch, corresponding to pixel resolutions of 72 to 100 ppi. With scanners, optical resolution is sometimes used to distinguish spatial resolution from the number of pixels per inch.

In geographic information systems (GISs), Spatial Resolution commonly refers to the Ground Sample Distance (GSD) of an image. Or in other words, how much of the earth's surface a single pixel covers.

In astronomy one often measures spatial resolution in data points per arcsecond subtended at the point of observation, since the physical distance between objects in the image depends on their distance away and this varies widely with the object of interest. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study On the other hand, in electron microscopy, line or fringe resolution refers to the minimum separation detectable between adjacent parallel lines (e. An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image g. between planes of atoms), while 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, while the latter (although more difficult to achieve) is key to visualizing how individual atoms interact.

Spectral resolution

Color images distinguish light of different spectra. A (digital color image is a Digital image that includes Color information for each Pixel. Multi-spectral images resolve even finer differences of spectrum or wavelength than is needed to reproduce color. Multi-spectral imaging is a technology originally developed for space-based imaging In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. That is, they can have higher spectral resolution. that is the stregth of each band that is created ( Lihongeni mulama: 2008)

Temporal resolution

Movie cameras and high-speed cameras can resolve events at different points in time. This article is about motion picture film cameras See Video camera for cameras which record images electronically A high speed camera is a device used for recording slow-motion playback films or used for scientific study of transient phenomena The time resolution used for movies is usually 15 to 30 frames per second (fps), while high-speed cameras may resolve 100 to 1000 fps, or even more. Frame rate, or frame frequency, is the measurement of the Frequency (rate at which an imaging device produces unique consecutive images called frames The

Many cameras and displays offset the color components relative to each other or mix up temporal with spatial resolution:

digital camera

LCD

CRT

Radiometric resolution

Main article: Bit depth

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 bits, for example 8 bits or 256 levels which is typical of computer image files. In Optics, radiometry is the field that studies the Measurement of Electromagnetic radiation, including Visible light. In Physics, intensity is a measure of the time-averaged Energy Flux. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication The higher the radiometric resolution, the better subtle differences of intensity or reflectivity can be represented, at least in theory. In photometry and Heat transfer, reflectivity is the fraction of incident radiation reflected by a surface 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 modern-day, digital-type measurements (and traditional, analog horizontal resolutions) for various media. The list only includes popular formats, not rare formats, and all values are approximate (rounded to the nearest 10), since 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 replaced "480" with "576". )

See also

External links

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