Image resolution
The image resolution is a colloquial measure of the size of an image raster graphics. It is given by the total number of pixels or the number of columns (width ) and rows ( height ) of a raster graphic.
- 6.1 computer
- 6.2 Video
- 6.3 Photography
Classification
The term resolution is used in practice ambiguous and in many areas, which can lead to misunderstandings. Resolution in a physical sense ( pixels per inch ) refers to the dot density of a playback or image scanning and thus - in addition to the color depth - a measure of the quality.
In raster graphics themselves that are present, for example, as a file, this quality can not be specified, because first it is unclear how the playback will be. Thus, a smaller, for example, only 200 bytes large favicon graphic file provide a quite " excellent and 100 % perfect " playback quality.
Resolution in the technical sense is based playback. As long as the playback is always physically on the same media, such as a 9 cm × 13 cm photographic print or identical televisions, which reached there quality also depends on the size of the original raster graphics. Since in general it is not clear how the output exactly done in all subsequent cases, the " resolution " does not serve as a direct measure of a general playback quality.
For technical processes that play a raster image, the larger the graphics ( " resolution " or image size in pixels)
- The better can be reached playback quality
- Or the greater can be played with the same quality.
Due to various technical factors, the relationship is not linear or restricted linear. In practice, one often tries to use as large a graph to at least not restrict subsequent playback quality from the outset. In individual cases, but this can also be disproportionately costly.
Representation of the size
The graph size can be represented in two versions:
In the second, more detailed variant, the ratio between width and height is obvious so that you get an idea of the aspect ratio.
In a graph are the pixels are not arranged in a geometrically regular grid but arbitrary, or has the image itself does not rectangular (or other periodic ) form, then as a resolution, only the total number of image points and perhaps their local density (per unit length or surface ) can be determined. An indication of the number of pixels product ( width x height) is then usually not possible. For example, in the silver halide photography, or LED traffic control systems, the discrete - can signal light points, only a few specified character representations, for example - not an image frame -filling - As speed limit - "80", "100" diagonal or in a double circle. Many LCDs use arrangements which do not correspond to a dot matrix, particularly in simple devices, such as Weather stations, digital clocks. These arrangements may well be more full-frame, because LCD pixels do not have to be rectangular. In line displays, which are mainly used for the display of text, the resolution is often specified in rows × columns, each column can represent one character. The same goes for the text mode in the field of computer graphics.
Screen display
In conventional analog CRT monitors, the format of the input signal (size in pixels ) is the same as the reproduced size, the pixels are transferred one- to-one. Depending on the playback electronics various graphic and video formats can be played with different image sizes ( in pixels ) from the device to the picture tube. The control electronics they are displayed on the screen always with the same width and height ( in general as a screen -filling full screen).
On a modern image display device such as a plasma or liquid crystal display screen, however, the playback screen makes it suitable fixed. It may differ from the format of the input signal. To correct possible of the number of pixels of width and height of the signal must then be transformed to the output grid ( scaled). This is, in particular in a reduction of loss of image content. But even at a magnification may be lost image information or image artifacts. The design and the technical effort, which is operated in the transformation that determines the quality of reproduction, especially the perceived quality.
Color depth
The depth of color indicates the fineness of graduations with which the color of individual pixels of a raster image can be reproduced. In addition to the number of pixels it is one of the defining parameters of a raster graphics.
Native Resolution
A resolution exactly to the physical digital resolution ( number of pixels ) corresponds to a display device is called the native resolution.
Knowing the native resolution of a display device is important because almost every resolution change a negative impact on the image quality effect (an exception is, for example, quadrupling the resolution at which the quality remains unchanged). If possible, the digital image should be changed only at one point of the signal path in his resolution, and directly in the native resolution of the display device.
Example: A photo with 6 megapixels is on a projector with WXGA (1280 × 800 ) display. The laptop to play has a resolution of 1680 × 1050 pixels. Would you use this resolution for the output to the projector on a laptop, the photo would have to be converted twice; only 6 megapixels to 1680 × 1050, and then again in the projector of 1680 × 1050 to 1280 × 800 It is better on the PC output is also set directly 1280 × 800, since the unique Convert lost less quality.
When CRT monitor
For CRT monitors, there is no "native resolution ", and also an optimal resolution can not be objectively calculated, but can only be estimated roughly. This has the following reasons:
For CRT monitors, the resolution is primarily limited by the focusing of the electron, as well as by the bandwidth that allows the electronics. The focusing of the electron beam is usually arbitrarily set via a hidden inside the monitor Poti. From the hole spacing can not draw conclusions on the factory or subsequently set focus.
Although the thickness of the electron beam is known, it can not be calculated the maximum resolution, since the individual lines may overlap slightly. You should abut at least, because otherwise the grid lines would be disruptive recognizable. However, overlap them too heavily, the image looks blurred. The optimal resolution thus becomes a question of taste.
In addition to black and white picture tubes, the phosphor screen has no structures, there are three types of color picture tubes: those with shadow mask with slit mask and aperture grille. With slit masks and shadow masks focusing the electron beam must be selected so that it is always the same covers a plurality of pixels, since otherwise it would come to moiré effects. The individual pixels of a slotted or perforated mask tube are individually addressable such as a TFT display in any case. The individual pixels therefore also not the "native resolution " represents the achievable resolution is rather something about it. In a stripe mask tube, it can not come to moiré effects, so that the focusing of the beam as a black and white picture tube does not have to take this into account. The strip mask thus limits the resolution only in the X direction. But again, that the individual subdivisions can not be individually controlled and the achievable resolution is slightly higher than the number of stripes.
Standards
Computer
In IT, there are various ( de facto ) standard video modes. These were defined by either the technical peculiarities of certain graphics standards or by the Video Electronics Standards Association ( VESA).
In practice, there are at desk and laptop monitors only the aspect ratios of 5:4 (1.25 ), 4:3 (1.33 ), 16:10 (1.6 ) and 16:9 (1.78 ). For different aspect ratios the graph is compressed or stretched when playing in width, in particular from 15:9 is usually 16:9. Some names, such as XGA, were washed out by the common advertising practice so that there are now a variety of interpretations of the original standards are - usually supplemented by additional letters - which are not part of the respective standards. Quad (Q ) represents a quadrupling of the number of pixels of the base size (doubling the width and height ), Quarter ( also Q ) for a quartering (halving the width and height ) and Hex ( H ) for a Versechzehnfachung ( quadrupling of width and height). In the widescreen sizes, the W is sometimes separated with a hyphen and / or take a back seat, for example: WXGA, WXGA, XGAW, XGA -W. The resolutions below the original VGA resolution today come mainly in mobile phone and PDA ads - often on edge. Modern computer monitors and graphics cards support image sizes up to 2560 x 1920 pixels.
A comprehensive overview list with pixels and aspect ratio information, please refer to graphics mode and image resolution in digital photography.
Video
Some video formats:
All video formats see video resolution
Photography
For the resolving power of films and optics see resolution ( photography).
In digital photography, the rounded total number of pixels is measured in megapixels ( MP) as a clue to the theoretically achievable quality. However, the actual image quality depends on many factors - the number of pixels alone leaves no statement. In fact, in the early years of digital photography, the number of pixels for reasons of cost was very limited and therefore the determining quality factor. Today, however, the optics and the noise performance of the sensor are often their quality.
In addition to an aspect ratio of 4:3, which often prevailed earlier, there is now, increasingly, the 3:2 format of the classic small picture. Cameras with native 16:9 format are still rare.
A list of common pixel arrangements can be found at the image sensor.