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Encyclopedia > Image resolution

Image resolution describes the detail an image holds. The term applies equally to digital images, film images, and other types of images. Higher resolution means more image detail. It has been suggested that this article or section be merged into image (disambiguation). ... A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels. ...


Image resolution can be measured in various ways. Basically, 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) 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. Look up vision in Wiktionary, the free dictionary. ... Photographic lens One of Canons most popular wide angle lenses - 17-40 f/4 L The zoom lens of the Canon Elph A photographic lens (or more correctly, objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images...

Contents

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. 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. 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 bounds on image resolution. This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen. ... This article or section does not cite any references or sources. ... The integers are commonly denoted by the above symbol. ... A pixel (a contraction of picture element) is one of the many tiny dots that make up the representation of a picture in a computers memory. ... The square shown above is 200 pixels by 200 pixels. ... In mathematics, especially in order theory, an upper bound of a subset S of some partially ordered set is an element which is greater than or equal to every element of S. The term lower bound is defined dually. ...


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 Image File history File links An illustration of the same image at different resolutions File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...


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. The square shown above is 200 pixels by 200 pixels. ...


The spatial resolution of computer monitors is generally 72 to 100 lines per inch, corresponding to pixel resolutions of 72 to 100 ppi.


In Geospatial Information Systems (GIS), 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. A geographic information system (GIS) is a system for capturing, storing, analyzing and managing data and associated attributes which are spatially referenced to the earth. ...


Spectral resolution

Color images distinguish light of different spectrum. Multi-spectral images resolve even finer differences of spectrum or wavelength than is needed to reproduce color. That is, they can have higher spectral resolution. A (digital) color image is a digital image that includes color information for each pixel. ... In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... Multi-spectral images are images of the same object (earth surface), taken in different bands of visible or infrared region of electromagnetic continuum. ... The wavelength is the distance between repeating units of a wave pattern. ...


Temporal resolution

Movie cameras and high-speed cameras can resolve events at different points in time. 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. The Arricam ST, a popular 35 mm film camera currently used on major productions. ... A high speed camera is a device used for recording slow-motion playback films. ... Frame rate, or frame frequency, is the measurement of how quickly an imaging device can produce several consecutive images, called frames. ...


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 bits, for example 8 bits or 256 levels which 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. In telecommunication and physics, radiometry is the science of radiation measurement. ... In physics, intensity is a measure of the time-averaged energy flux. ... This article is about the unit of information. ... In optics, reflectivity is the reflectance (the ratio of reflected power to incident power, generally expressed in decibels or percentage) at the surface of a material so thick that the reflectance does not change with increasing thickness; , the intrinsic reflectance of the surface, irrespective of other parameters such as the...


Resolution in various media

  • DVDs encode 720 by 480 (NTSC) pixels or 720 by 576 (PAL) pixels
  • Blu-ray disks encode 1920 by 1080 pixels
  • High definition television is 1920 by 1080 pixels or 1280 by 720 pixels
  • 35 mm film is scanned for release on DVD at 1080 or 2000 lines as of 2005.
  • 35 mm original camera negative motion picture film can resolve up to 6,000 lines.
  • 35 mm projection positive motion picture film has about 2,000 lines which results from the analogue printing from the camera negative of an interpositive, and possibly an internegative, then a projection positive.
  • Sequences from newer films are scanned at 2,000, 4,000 or even 8,000 columns (line measured the other directions), called 2K, 4K and 8K, for quality visual effects editing on computers.

Size comparison: A 12 cm Sony DVD+RW and a 19 cm Dixon Ticonderoga pencil. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... Television encoding systems by nation. ... Blu-ray discs Blu-ray Disc is a next-generation optical disc format jointly developed by a group of leading consumer electronics and PC companies called the Blu_ray Disc Association (BDA), which succeeds the Blu_ray Disc Founders (BDF). ... High-definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. ... 35 mm film frames. ... The original camera negative is the film in a motion picture camera that captures the original image. ... This article is about digital presentation. ...

See also

Display standards comparison The display resolution of a digital television or computer display typically refers to the number of distinct pixels in each dimension that can be displayed. ... Suppose the smiley face in the top left corner is an RGB bitmap image. ... Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ...

External links

  • Pixel & Resolution Tables; practical tables, and theory for beginner's education about resolution issues in digital imaging, photo and printing.
  • Luminous Landscape's Res-Demyst; on why pixel count is not always a good proxy for resolution
  • Cintel: 4K; on a 4000-column film scanning system
  • Northlight Film Scanner: On a 8000-column film scanning system

  Results from FactBites:
 
Image resolution - Wikipedia, the free encyclopedia (1621 words)
For digital raster-images, the convention is to describe the image 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).
In sampled images or other sampled data, the resolution should usually not exceed the sampling rate, or there will be aliasing.
Resolution can be a measurement of the total number of pixels displayed but this applies mainly to static images and can be affected by how it is displayed.
Image Resolution (893 words)
However, although the term is not effective, image resolution commonly is referred to in dots per inch (dpi)—dpi more appropriately is attributed to device resolution or output resolution, where the number of dots an output device is able to produce within an inch represents the resolution of the device.
Output resolution for computer-to-plate devices (i.e., platesetters) typically is about 2400dpi; however, because no significant visible improvement is realized when 2400ppi and 1200ppi monochrome images are compared, the range for monochrome image resolution is suggested as 900-1200ppi.
This recommended resolution, as well as ranges suggested for other file types, assumes that images have been scanned at the same size intended for print (e.g., the typical image width is approximately 20 picas, or 3 1/3 inches, for a single-column image that will appear in a double-column standard size publication).
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