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

Google Tech Talks January, 25 2008 ABSTRACT 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.