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Computational photography refers to digital image capture and processing techniques that use digital computation instead of optical processes. Computational photography can improve the capabilities of a camera, or introduce features that were not possible at all with film-based photography, or reduce the cost or size of camera elements. Examples of computational photography include in-camera computation of digital panoramas, high-dynamic-range images, and light field cameras. Light field cameras use novel optical elements to capture three dimensional scene information which can then be used to produce 3D images, enhanced depth-of-field, and selective de-focusing (or "post focus"). Enhanced depth-of-field reduces the need for mechanical focusing systems. All of these features use computational imaging techniques. The definition of computational photography has evolved to cover a number of subject areas in
computer graphics Computer graphics deals with generating images and art with the aid of computers. Computer graphics is a core technology in digital photography, film, video games, digital art, cell phone and computer displays, and many specialized applications. ...
,
computer vision Computer vision tasks include methods for image sensor, acquiring, Image processing, processing, Image analysis, analyzing, and understanding digital images, and extraction of high-dimensional data from the real world in order to produce numerical ...
, and applied
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...
. These areas are given below, organized according to a taxonomy proposed by Shree K. Nayar. Within each area is a list of techniques, and for each technique one or two representative papers or books are cited. Deliberately omitted from the taxonomy are
image processing An image or picture is a visual representation. An image can be two-dimensional, such as a drawing, painting, or photograph, or three-dimensional, such as a carving or sculpture. Images may be displayed through other media, including a pr ...
(see also digital image processing) techniques applied to traditionally captured images in order to produce better images. Examples of such techniques are image scaling, dynamic range compression (i.e. tone mapping), color management, image completion (a.k.a. inpainting or hole filling), image compression, digital watermarking, and artistic image effects. Also omitted are techniques that produce range data, volume data, 3D models, 4D light fields, 4D, 6D, or 8D
BRDF The bidirectional reflectance distribution function (BRDF), symbol f_(\omega_,\, \omega_), is a function of four real variables that defines how light from a source is reflected off an Opacity (optics), opaque surface. It is employed in the optic ...
s, or other high-dimensional image-based representations. Epsilon photography is a sub-field of computational photography.


Effect on photography

Photos taken using computational photography can allow amateurs to produce photographs rivalling the quality of professional photographers, but do not outperform the use of professional-level equipment.


Computational illumination

This is controlling photographic illumination in a structured fashion, then processing the captured images, to create new images. The applications include image-based relighting, image enhancement, image deblurring, geometry/material recovery and so forth. High-dynamic-range imaging uses differently exposed pictures of the same scene to extend dynamic range. Other examples include processing and merging differently illuminated images of the same subject matter ("lightspace").


Computational optics

This is capture of optically coded images, followed by computational decoding to produce new images. Coded aperture imaging was mainly applied in astronomy or X-ray imaging to boost the image quality. Instead of a single pin-hole, a pinhole pattern is applied in imaging, and deconvolution is performed to recover the image. In coded exposure imaging, the on/off state of the shutter is coded to modify the kernel of motion blur. In this way motion deblurring becomes a well-conditioned problem. Similarly, in a lens based coded aperture, the aperture can be modified by inserting a broadband mask. Thus, out of focus deblurring becomes a well-conditioned problem. The coded aperture can also improve the quality in light field acquisition using Hadamard transform optics. Coded aperture patterns can also be designed using color filters, in order to apply different codes at different wavelengths. This allows to increase the amount of light that reaches the camera sensor, compared to binary masks.


Computational imaging

Computational imaging is a set of imaging techniques that combine data acquisition and data processing to create the image of an object through indirect means to yield enhanced resolution, additional information such as optical phase or 3D reconstruction. The information is often recorded without using a conventional optical microscope configuration or with limited datasets. Computational imaging allows to go beyond physical limitations of optical systems, such as
numerical aperture In optics, the numerical aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. By incorporating index of refraction in its definition, has the property ...
, or even obliterates the need for optical elements. For parts of the optical spectrum where imaging elements such as objectives are difficult to manufacture or image sensors cannot be miniaturized, computational imaging provides useful alternatives, in fields such as
X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
and THz radiations.


Common techniques

Among common computational imaging techniques are lensless imaging, computational speckle imaging,Katz et al.
"Non-invasive single-shot imaging through scattering layers and around corners via speckle correlations"
''Nature Photonics'' 8, 784–790 (2014)
ptychography and Fourier ptychography. Computational imaging technique often draws on compressive sensing or phase retrieval techniques, where the angular spectrum of the object is being reconstructed. Other techniques are related to the field of computational imaging, such as digital holography,
computer vision Computer vision tasks include methods for image sensor, acquiring, Image processing, processing, Image analysis, analyzing, and understanding digital images, and extraction of high-dimensional data from the real world in order to produce numerical ...
and inverse problems such as tomography.


Computational processing

This is processing of non-optically-coded images to produce new images.


Computational sensors

These are detectors that combine sensing and processing, typically in hardware, like the oversampled binary image sensor.


Early work in computer vision

Although computational photography is a currently popular buzzword in computer graphics, many of its techniques first appeared in the computer vision literature, either under other names or within papers aimed at 3D shape analysis.


Art history

Computational photography, as an art form, has been practiced by capture of differently exposed pictures of the same subject matter, and combining them together. This was the inspiration for the development of the
wearable computer A wearable computer, also known as a body-borne computer, is a computing device worn on the body. The definition of 'wearable computer' may be narrow or broad, extending to smartphones or even ordinary wristwatches. Wearables may be for general ...
in the 1970s and early 1980s. Computational photography was inspired by the work of Charles Wyckoff, and thus computational photography datasets (e.g. differently exposed pictures of the same subject matter that are taken in order to make a single composite image) are sometimes referred to as Wyckoff Sets, in his honor. Early work in this area (joint estimation of image projection and exposure value) was undertaken by Mann and Candoccia. Charles Wyckoff devoted much of his life to creating special kinds of 3-layer photographic films that captured different exposures of the same subject matter. A picture of a nuclear explosion, taken on Wyckoff's film, appeared on the cover of ''Life'' Magazine and showed the dynamic range from dark outer areas to inner core.


See also

* Adaptive optics *
Comparison of raster graphics editors Raster graphics editors can be compared by many variables, including availability. List General information Basic general information about the editor: creator, company, license, etc. Operating system support The operating systems on ...
* Multispectral imaging * Simultaneous localization and mapping *
Super-resolution microscopy Super-resolution microscopy is a series of techniques in optical microscopy that allow such images to have Optical resolution, resolutions higher than those imposed by the Diffraction-limited system, diffraction limit, which is due to the diffra ...
* Time-of-flight camera


References


External links

* Nayar, Shree K. (2007)
"Computational Cameras"
''Conference on Machine Vision Applications''.
''Computational Photography'' (Raskar, R., Tumblin, J.,)
A.K. Peters. In press.
Special issue on Computational Photography
IEEE Computer, August 2006.
Camera Culture and Computational Journalism: Capturing and Sharing Visual Experiences
{{Webarchive, url=https://web.archive.org/web/20150906055242/http://www.computer.org/portal/web/computingnow/cgacfp1 , date=2015-09-06 , IEEE CG&A Special Issue, Feb 2011. * Rick Szeliski (2010),
Computer Vision: Algorithms and Applications
', Springer. * Computational Photography: Methods and Applications (Ed. Rastislav Lukac), CRC Press, 2010.

(John Wiley and Sons book information).


GJB-1: Increasing the dynamic range of a digital camera by using the Wyckoff principleExamples of wearable computational photography as an art formSiggraph Course in Computational Photography
Digital photography Computational fields of study Computer vision