PhotoTechEDU Day 32 - Art, Science and Reality of High Dynamic Range (HDR) Im...





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Uploaded on Jan 26, 2008

Google Tech Talks
January, 25 2008


High Dynamic Range (HDR) image capture and display has become an
important engineering topic. The discipline of reproducing scenes with
a high range of luminances has a five-century history that includes
painting, photography, electronic imaging and image processing. HDR
images are superior to conventional images. There are two fundamental
scientific issues that control HDR image capture and reproduction. The
first is the range of information that can be measured using different
techniques. The second is the range of image information that can be
utilized by humans. Optical veiling glare severely limits the range of
luminance that can be captured and seen.

In recent experiments, we measured camera and human responses to
calibrated HDR test targets. We calibrated a 4.3-log-unit test target,
with minimal and maximal glare from a changeable surround. Glare is an
uncontrolled spread of an image-dependent fraction of scene luminance
in cameras and in the eye. We use this standard test target to measure
the range of luminances that can be captured on a camera's image
plane. Further, we measure the appearance of these test luminance
patches. It is the improved quantization of digital data and the
preservation of the scene's spatial information that cause the
improvement in quality in HDR reproductions. HDR is better than
conventional imaging, despite the fact the multiple- exposure-HDR
reproduction of luminance is inaccurate. This talk describes the
history of HDR image processing techniques including painting,
photography, and electronic image processing (analog and digital) over
the past 40 years. It reviews the development of Retinex theory, and
other spatial-image- processing algorithms, that calculate appearance
in images from arrays of radiances.

Speaker: John McCann
John McCann received a B.A. degree in Biology from Harvard University
in 1964. He worked in, and later managed, the Vision Research
Laboratory at Polaroid from 1961 to 1996. He has studied human color
vision, digital image processing, large format instant photography and
the reproduction of fine art. He is a Fellow of IS&T. He is a past
President of IS&T and the Artists Foundation, Boston. He is currently
consulting and continuing his research on color vision. He is the
IS&T/OSA 2002 Edwin H. Land Medalist and IS&T 2005 Honorary Member and
will be a 2008 Fellow of the Optical Society of America.


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