Abstract
Retinex Imaging shares two distinct elements: first, a model of human color vision; second, a spatial-imaging algorithm for making better reproductions. Edwin Land’s 1964 Retinex Color Theory began as a model of human color vision of real complex scenes. He designed many experiments, such as Color Mondrians, to understand why retinal cone quanta catch fails to predict color constancy. Land’s Retinex model used three spatial channels (L, M, S) that calculated three independent sets of monochromatic lightnesses. Land and McCann’s lightness model used spatial comparisons followed by spatial integration across the scene. The parameters of their model were derived from extensive observer data. This work was the beginning of the second Retinex element, namely, using models of spatial vision to guide image reproduction algorithms. Today, there are many different Retinex algorithms. This special section, “Retinex at 50,” describes a wide variety of them, along with their different goals, and ground truths used to measure their success. This paper reviews (and provides links to) the original Retinex experiments and image-processing implementations. Observer matches (measuring appearances) have extended our understanding of how human spatial vision works. This paper describes a collection very challenging datasets, accumulated by Land and McCann, for testing algorithms that predict appearance.
Highlights
Edwin Land coined the word “Retinex” in 1964.1 He used it to describe the theoretical need for three independent color channels to explain human color constancy
This experiment led to Land and McCann’s model of calculated lightness. It introduces the need for observer data to define the spatial properties of a model of lightness. It describes the use of observer data to understand the spatial processing of human vision, including appearance in high-dynamic range (HDR) scenes influenced by intraocular glare
Color sensations do not correlate with surface reflectances in complex natural scenes
Summary
Edwin Land coined the word “Retinex” in 1964.1 He used it to describe the theoretical need for three independent color channels to explain human color constancy. Land had enthusiastically experimented with two-color projections in the late 1950s and early 1960’s.2 By that time, he had hundreds of patents on many different photographic systems. He was well aware of the possibilities, and limitations, of silver halide photography Before his “Red and White” light projection experiments, he accepted the standard explanation of color, namely, color was the result of the local quanta catches of receptors with different spectral sensitivities. The color appearances in those projections could not be understood from the quanta catches of receptors in a tiny local region He realized that human color appearances are fundamentally different: spatial comparisons control color sensations. Perhaps Land’s greatest contribution to vision research is the remarkable legacy of fascinating, simple but elegant, experiments His “Red and White” projections, “Color and Black & White Mondrians,” changed the requirements of vision theories. Color is the comparison of L, M, S Retinex monochromatic lightnesses
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