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A Multiscale Retinex For Color Rendition and Dynamic Range Compression Ziaur Rahman y
 

Summary: A Multiscale Retinex For Color Rendition and Dynamic Range Compression
Zia­ur Rahman y
College of William & Mary, Williamsburg, VA 23187
Daniel J. Jobson and Glenn A. Woodell
NASA Langley Research Center, Hampton, Virginia 23681
Abstract
The human vision system performs the tasks of dynamic range compression and color constancy almost
effortlessly. The same tasks pose a very challenging problem for imaging systems whose dynamic range is restricted
by either the dynamic response of film, in case of analog cameras, or by the analog­to­digital converters, in the
case of digital cameras. The images thus formed are unable to encompass the wide dynamic range present in most
natural scenes (often ? 500:1). Whereas the human visual system is quite tolerant to spectral changes in lighting
conditions, these strongly affect both the film response for analog cameras and the filter responses for digital
cameras, leading to incorrect color formulation in the acquired image. Our multiscale retinex, based in part on
Edwin Land's work on color constancy, provides a fast, simple, and automatic technique for simultaneous dynamic
range compression and accurate color rendition. The retinex algorithm is non­linear, and global---output at a
point is also a function of its surround---in extent. A comparison with conventional dynamic range compression
techniques such as the application of point non­linearities, e.g. log(x; y), and global histogram equalization and/or
modification shows that the multiscale retinex simultaneously provides the best dynamic range compression and
color rendition. The applications of such an algorithm are many; from medical imaging to remote sensing; and
from commercial photography to color transmission.

  

Source: Ahumada Jr., Al - Vision Science and Technology Group, Human Factors Research and Technology Division, NASA Ames Research Center

 

Collections: Engineering