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Digital zoom is a method of decreasing the preciseangle of view of adigital photograph orvideo image. It is accomplished bycropping an image down to an area with the sameaspect ratio as the original, andscaling the image up to the dimensions of the original. The camera's optics are not adjusted. It is accomplished electronically, so nooptical resolution is gained.[citation needed] Digital zooming may be enhanced by computationally expensive algorithms which sometimes involves artificial intelligence.[1]
In cameras that performlossy compression, digital zoom is preferred to enlargement in post-processing, as the zooming may be applied before detail is lost to compression. In cameras that save in a lossless format, resizing in post-production yields results equal or superior to digital zoom.[citation needed]
Lower-endcamera phones use only digital zoom and do not have optical zoom, while many higher-end phones haveadditional rear cameras, including fixed telephoto lenses that allow for the simulation of optical zoom. Full-sized cameras generally have anoptical zoom lens, but some apply digital zoom automatically once the longest opticalfocal length possible has been reached. Professional cameras generally do not feature digital zoom.[citation needed]
Anoptical zoom camera can be zoomed to its optical limit, and further zooming is sometimes allowed by digital zoom. Digital zoom uses the centre area of the optical image to enlarge the image. By reducing the image size, digital zoom occurs without image deterioration of the output image, and some cameras have a "not-deteriorated image" mode or an image deterioration indicator.[2][3]
The table below shows the not-deteriorated zoom limit for somemegapixel (MP) image sizes of a particular camera with optical zoom 24x, and digital zoom 4x for its maximum capability:
| Image size | Maximum zoom factor | Not-deteriorated zoom limit | Magnification of digital zoom |
|---|---|---|---|
| 16 MP | 96.0× | 24.0× | 1.0× |
| 10 MP | 121.2× | 30.2× | 1.3× |
| 5 MP | 172.8× | 43.2× | 1.8× |
| 3 MP | 215.5× | 54.0× | 2.25× |
| VGA | 382.6× | 172.8× | 7.2× |
Some camerafirmwares store lossily digitally zoomed images with accordingly reduced dimensions (width and height) rather than upscaling it to the originalraster resolution. The benefits are reduced file sizes and the ability to calculate the zoom level from the image's dimensions, if not included in itsmeta data.[citation needed]
Cameras may have an intelligent zoom feature that allows an additional magnification of 2.0× on top of its optical zoom. Many cameras have 2 options: 1.4× and 2.0×.[citation needed] The intelligent zoom only uses the centre of theimage sensor and does not interpolate the original resolution, so the resulting image quality is good in reduced resolution.[4]
Hybrid zoom is a concept used in smartphones that takes advantage of optical zoom, digital zoom, and software to get improved results when zooming in further than the lens' physical capabilities.[5] Smartphones with optical zoom have lenses with 3× or 5× magnification. Trying to zoom in further than this limit may result in loss of quality as the camera switches to digital zoom, though hybrid zoom may mitigate this. Many cameras, includingmobile phone cameras, also employ lossless digital zoom for video recording by using the spare resolution of the image sensor for cropping by taking advantage of used video frame resolutions often being significantly below the available resolution of the image sensors.[4]
This means that, for example, if implemented correctly by the camera hardware and software, a2160p image sensor would enable up to 2× lossless digital zoom for1080p video recording, 3× for720p video, and 4.5× for480p video by using image sensor cropping.
The terms among camera and image sensor manufacturers are "Smart Zoom" (Sony), "Safe Zoom" (Canon), "Sensor Crop" (Cisco)[4] and "Intelligent Zoom" (Panasonic and others).[6] There are also cameras with digital zoom functions as high as 7.2× and Smart Zoom with approximately 30× total zoom (optical zoom 20× and digital zoom 1.5×) for 7MP from 16MP total resolution, and also 144× total zoom (optical zoom 20× and digital zoom 7.2×) for VGA 640x480.[7]
Photographers can purposefully employ digital zoom for the characteristic low-fidelity appearance of the images it produces.[8] The appearance of poor quality in photographs can be intentionally used to imply carelessness on the part of the photographer and a sense of candidness in the photograph.