Digital zoom

Zooming
Digital zoom has been used to make the middle photo from the top photo, image quality is lost, while the lens was zoomed-in optically for the bottom photo, no quality is lost. Typically, the digital zoom would not be available until after the optical zoom had been exhausted.

Digital zoom is a method of decreasing the apparent angle of view of a digital photographic or video image. Digital zoom is accomplished by cropping an image down to a centered area with the same aspect ratio as the original, and usually interpolating the result back up to the pixel dimensions of the original. It is accomplished electronically, with no adjustment of the camera's optics, and no optical resolution is gained in the process.[1]

When comparing the image quality achieved by digital zoom with image quality delivered by resizing the image in post-processing, there's a difference between cameras that perform potentially lossy image compression like JPEG and those that save images in an always lossless Raw image format. In the former case, the digital zoom tends to be superior to enlargement in post-processing, because the camera may apply its interpolation before detail is lost to compression. In the latter case, resizing in post-production yields results equal or superior to digital zoom.

Modest camera phones use only digital zoom and have no optical zoom at all. Usually, cameras have an optical zoom lens but apply digital zoom automatically once its longest optical focal length has been reached. Professional cameras generally do not feature digital zoom.

Not deteriorated (optical+digital) zoom limitEdit

The optical zoom camera can be set first before its maximum and is then followed by its digital zoom in video mode only. Still, most cameras use digital zoom after the optical zoom reaches the maximum for photo and video. Digital zoom uses the centre area of the optical image to enlarge the image. By reducing the MP image size, using digital zoom can be done without image deterioration, and some cameras have a not deteriorated image mode or at least has Image deterioration indicator.[2][3]

The table below shows the not deteriorated (optical+digital) zoom limit for some MP image size of a certain camera with Optical zoom 24x and Digital zoom 4x for its maximum capability:

Image Size Maximum Zoom Factor Undeteriorated zoom limit Magnification of digital zoom
16 MP 96.0× 24.0× 1.0×
10 MP 121.2× 30.2× 1.3×
7 MP(*) 1.5×
5 MP 172.8× 43.2× 1.8×
3 MP 215.5× 54.0× 2.25×
2 MP(*) 2.8×
VGA 382.6× 172.8× 7.2×

Note: These lines are interpolation.

When using digital zoom for a photo, the not deteriorated digital zoom limit is 1.3×, 1.8× and 2.25× respectively for 10  MP, 5  MP and 3  MP, but when using VGA, the image quality is always good under not deteriorated digital zoom limit, because the digital zoom is only maximum 4×, while the limit is 7.2×, but some cameras with 16  MP have digital zoom up to 7.2× or using the capability to the edge for VGA. The table above has also shown that from 3 MP jumps directly too much too VGA and this camera has no option of 2 MP (1920x1080) and 1.3 MP, but other cameras have it.[4]

When using digital zoom for video recording in this example, the camera can take up to 382.6× magnification in VGA with Deteriorated image quality, and up to 172.8× with not deteriorated image quality. But because videos are recorded at multiple frames per second, the perceived quality between the deteriorated image quality and not deteriorated image quality may not be much different.[5]

Nowadays[when?], cameras usually 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 the image sensor and doesn't make any interpolation of the original resolution, so the resulting image quality is good (optical zoom) in reduced resolution.[6]

Many cameras, including mobile phone cameras, also employ lossless digital zoom for video recording by using the spare resolution of the image sensor for cropping, taking advantage of used video frame resolutions often being significantly below the available resolution of the image sensor.[6]

The terms among camera and image sensor manufacturers are "Smart Zoom" (Sony), "Safe Zoom" (Canon), "Sensor Crop" (Cisco)[6] and "Intelligent Zoom" (Panasonic and others).[7] There are also cameras with digital zooms as high as 7.2× and SmartZoom 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.[8]

AestheticEdit

Some photographers purposefully employ digital zoom for the characteristic low-fidelity appearance of the images it produces.[9] This community thinks that poor quality photographs imply the carelessness of the photographer and thus the candidness of the photograph. The notion that it is possible to achieve authenticity through premeditated carelessness also inspires lo-fi music.[10]

See alsoEdit

ReferencesEdit

  1. ^ "Zoom Digital". Retrieved September 29, 2016.[permanent dead link]
  2. ^ "Casio EXILIM EX-H50 User Manual: Shooting With Zoom". Retrieved February 19, 2015.
  3. ^ "Casio EXILIM EX-H50 User Manual Page 43". Retrieved February 19, 2015.
  4. ^ "FinePix T400, T350 / T360". Archived from the original on May 12, 2015. Retrieved April 22, 2015.
  5. ^ "Casio EXILIM EX-H50 User Manual Page 44". Retrieved February 19, 2015.
  6. ^ a b c Getting lossless zoom with sensor crop - Cisco Meraki blog
  7. ^ "Optical vs. Digital Zoom". Retrieved February 27, 2015.
  8. ^ "Pentax Optio VS20Hot". Retrieved June 6, 2015.
  9. ^ "How I Learned to Love Digital Zoom". Retrieved October 14, 2016.
  10. ^ "Revealing the Hollow Reality of Lo-Fi". Retrieved October 14, 2016.