Pixel#Megapixel
Megapixel is based on the SI prefix for a million picture elements (pixels ) and is the most common unit used to indicate the sensor and image resolution in digital photography. In advertising, this number a long time served as a largely single feature for evaluating a digital camera.
A common abbreviation has not yet naturalized, are in common use both " MP " and " mpx ", " Mpix " and " megapixels ". To specify the physical resolution of the camera manufacturers count each color (sub - ) pixel individually, so each red, blue or green ( sub) sensor of a Bayer sensor. The number of pixels a camera has, therefore, not comparable with the pixel specified in a screen. Higher resolutions allow larger sized photo prints, as the number of pixels per area larger, so the grid is smaller. For the image quality significantly, the physical pixels of the image sensor, not the artificially calculated by interpolation.
Problem
Most digital cameras have primarily changed in recent years in two characters. Firstly, the number of pixels ( the end of 2008 or even 14 Megapixel still end 2010 Balance ) has increased to now mostly well over ten megapixels; second, the image sensors became smaller. Thus, the size of the image sensors in the years has halved from 2005 to 2010 of approximately 60 mm ² to 30 mm ², while the overall resolution is increased four times - the individual pixels were thus only one-eighth as large as five years earlier. However, given the effects of misinformation in relation to the actual image information more in a smaller area, it comes to the so-called noise. This is particularly at higher sensor sensitivities ( in analogy to the previous film speeds ) or dark image areas in a problem. This problem affects primarily at a 1:1 view when you zoom much closer in the image compared to an image of a low -resolution camera. In an equally large issue, the problem flattened out since the misinformation spread again on several pixels. But in order to work around this problem, even with large output formats, use modern cameras increasingly noise reduction method that try these artifacts at the expense of image clarity or to correct by loss of detail. However, very small pixel sizes limit the freedom in the choice of the f-number.
As an advantage, but it remains to create smaller cutouts in still sufficient resolution just for cameras with the conventional Bayer sensor has a lower sensitivity for the moiré effect and the possibility.
Furthermore, it comes with too small pixels susceptible to diffraction of light. Sensor pixels smaller than three microns are therefore unsuitable.
In contrast, digital system cameras ( DSLR) and most have larger sensors (often APS -C with about 350 mm ²), a pixel size would have a resolution of 37 megapixels, for example, correspond to a modern compact camera with only three megapixels. Noise often occurs when these cameras to not as strong as for models with smaller sensors. With increasing number of megapixels beyond 20 and different equipment are general statements regarding the noise behavior is not possible. With the same number of megapixels larger sensors smaller type of construction are in terms of image noise at an advantage, but at the expense of depth of field. For the same depth of field has to be dimmed, so that the sensor sensitivity increases and connected with it again the noise. Is, however, especially with very large numbers of pixels, the image noise is no longer visible at the pixel level in the overall picture, since the playback media, such as screens or prints, as well as the human retina are not able to resolve as many individual pixels so that interpolated, whereby the image error distributed.
Large image sensors are also used in a few compact cameras the upper price ranges.
A middle ground is called the Micro Four Thirds standard, in which an image sensor with the size designation 4/3 " and an area is used by approximately 225 mm ². This is the production of relatively small and lightweight cameras that allow with yet low-noise images.
Video cameras
A similar trend is observed in video cameras. Although this increases the number of pixels only slightly, but the image sensors are still further reduced in non-professional cameras, to extract ever greater zoom ranges from consistently compact and affordable lenses.