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Digital and ComputationalPhotography
Av: Piraachanna Kugathasan
What is computational photography
• Digital photography:
– Simply replaces traditional sensors and recording by
digital technology
– Involves only simple image processing
• Computational photography
– More elaborate image manipulation, more
computation
– New types of media (panorama, 3D, etc.)
– Camera design that take computation into account
Computational photography
• Computational illumination
• Computational optics
• Computational processing
• Computational sensors
Computational illumination• Controlling photographic illumination in a structured fashion,
then processing the captured images, to create new images
• ‐Flash/no‐flash imaging
• ‐Multi‐flash imaging
• ‐Different exposures imaging
• ‐Image‐based Relighting
Computational optics
• Capture of optically coded images, followed by computational decoding to produce new images
• ‐ Coded aperture imaging
• ‐ Coded exposure imaging
• ‐light field photography
• ‐Catadioptric imaging
• ‐Wavefront coding
• ‐ Compressive imaging
Computational processing
• Processing of non‐optically coded images to produce new images
• ‐ Panorama mosaicing
• ‐Matte extraction
• ‐ Digital photomontage
• ‐ High dynamic range imaging
• ‐ All‐focus imaging
Computational sensors
• Detectors that combine sensing and processing, typically in hardware.
• ‐ Artificial retinas
• ‐ High dynamic range sensors
• ‐ Retinex sensors
Tone mapping
A simple example of global tone mapping filter
Defocus Matting
Super‐resolution
• Get a sharp high resolution image from low resolution
The A‐Cam
The A‐Cam is a collection of three video cameras that share a single center of projection by using a tree of beam splitters
Results from the A‐Cam
a)pinhole image of the A‐Cam, (b) background focused image, (c) foreground focused image, (d) automatically computed trimap, (e) the alpha matte at the A‐Cam resolution, (f) the super‐resolution alpha matte, and (g) super‐resolution alpha premultiplied foreground image composited with a new background.
Revolution 1: The invention of optical instruments
Computational ImagingTwo revolutions
Imaging without optics
Imaging with optics
Revolution 2: Electronic Recording
Electronic recording enables
• Electronic transmission (television)
• Multidimensional imaging (tomography)
• Feature extraction/enhancement
• Computational improvement of image metrics– Enhanced resolution
– Extended depth of field
– Imaging of spectra, coherence and polarization features
– ….
History of traditional and digital photo
• http://www.digicamhistory.com/
First production camera
1839. Daguerrotype
Instant photography
First TV
Transmission of moving images• 1884 ‐ Paul Nipkow– Using rotating disk with raster spiral– But amplification problems
Color TV
• First broadcast in 1951, CBS
Computer Graphics
• Computers to create image
• Sketchpad, 1961, Ivan Sutherland’s MIT PhD thesis
First digital camera
• 1975, Steve Sasson, Kodak• Uses ccd from Fairchild semiconductor, A/D from Motorola, .01 megapixels, 23 second exposure, recorded on digital cassette
Paint program
• Dick Shoup: SuperPaint [1972‐73]– 8 bits– http://www.rgshoup.com/prof/SuperPaint/• Alvy Ray Smith (Pixar co‐founder): Paint [1975‐77] – 8 bits then 24 bits– http://www.alvyray.com/Awards/AwardsMain.htm– http://www.alvyray.com/Bio/BioMain.htm• Tom Porter: Paint
Photoshop
• Thomas Knoll and John Knoll began development in 1987
• Version 1.0 on Mac: 1990• http://en.wikipedia.org/wiki/Photoshop#Development• http://www.storyphoto.com/multimedia/multimedia_photoshop.html
Internet photo browsing• (Web browser that can display photos)• Mosaics, NCSA, Urbana Champaign, 1992
Camera advice
Equipment• Do get an SLR, compacts are way too limited• Don't worry about brand• Don't worry about the body, get the cheapest one• Worry about lenses– Zooms are convenient but quality can be a problem• avoid the basic zoom, but the one above is usually great• Maximum aperture matters (the smaller the number, the better)– Get a prime in the 35‐85mm range (cheap, high quality, wide aperture)50mm f/1.8 (both Canon & Nikon)
• Get a tripod• Get an external flash if you want to take “event” pictures– And orient towards ceiling– Good flash photography is very difficult
• Count 4k for camera+standard zoom+50mm
Brands• Nikon
– most used, cheap, great body, good images
• Canon
– user friendly, good images
• Olympus
– Good system, but smaller sensor
• Konica‐Minolta
– Just announced they stop photography!
• Pentax
– Good entry camera
• Sigma
– Intriguing sensor (Foveon)
• Fuji
– One‐trick pony (the sensor)
– Nikon body
• Sony
– Very silent, good images, lot of functions
Shooting
• Use aperture priority, work on depth of field
• Change your viewpoint
• Don't center things
• Learn to adjust ISO
• Shoot raw
• Check your histogram
Editing (Photoshop)
• Crop to improve composition
• Manage contrast using curve and adjustment layers
• Sharpen a bit
• Convert to black and white with gradient map
Refs
• Wikipedia
• http://projects.csail.mit.edu/photo/
• http://en.wikipedia.org/wiki/Computational_photography#Computational_optics
• http://www.digicamhistory.com/
• Google.com ☺