Color image reproduction of scenes with color enhancement and preferential tone mapping

A system for making a visual reproduction of an original scene with preferential tone mapping and color enhancement, the system being of the type having means for capturing original scene parameters onto a medium from which a visual reproduction of the original scene is to be derived and means for creating a visual reproduction of the scene from the captured scene parameters;

• said system characterized by:
• transformation means for imparting to the visual reproduction to be created, when taken in conjunction with untransformed characteristics of the capturing and creating means, a reproduction which satisfies the following two requirements:
• (a) the reproduction has a reproduced tone mapping having instantaneous gamma values of viewed reproduction density relative to density of the original scene which are greater than a minimum value of A and less than A plus 0.35 times scene exposure density over a scene exposure density range of from 0.60 to 1.45 as measured relative to a zero density, 100% diffuse reflector in the original scene, the instantaneous gamma values within scene exposure density range further lying entirely within a range of values subtended by an angle of 14.degree. measured from a reference point at 0.0 scene exposure density and a viewed reproduction density gradient of A, wherein A is 1.0 in the case of direct view reflection media reproduction, 1.1 in the case of self-illuminated reproduction for viewing with ambient surround, and 1.3 in the case of a reproduction for viewing with dark surround;
• and
• (b) the reproduction has color enhancement wherein a Macbeth Color Checker, if captured in the original scene, would appear in the reproduced image so that (1) the CIELAB chroma ratio is greater than 1/A for at least one of the six high chroma patches (the row above the grey scale), and (2) either the CIELAB chroma ratio for the light skin patch is between 0.8/A and 1.4/A or the CIELAB chroma ratio for the dark skin patch is between 1.0/A and 1.8/A, or the CIELAB chroma ratios for both skin patches are within said ranges, wherein A is as defined in (a) above.

A system for modifying tone mapping and providing color enhancement to an image of original scene parameters captured on an image capture medium from which a visual reproduction of the original scene is to be created on a viewable output medium, said system comprising:

• means for converting said image on said image capture medium to a series of image pixel signals having amplitudes related to density values of said image pixels;
• and
• image processing means for modifying said image pixel signal amplitudes to impart a predetermined transformation of said original scene parameters, said transformation being such that, taken in conjunction with untransformed characteristics of said image capture medium and image reproduction output medium, results in modifying the parameters to create a reproduction which satisfies the following two requirements:
• (a) the reproduction has a reproduced tone mapping having instantaneous gamma values of viewed reproduction density relative to density of the original scene which are greater than a minimum value of A and less than A plus 0.35 times scene exposure density over a scene exposure density range of from 0.60 to 1.45 as measured relative to a zero density, 100% diffuse reflector in the original scene, the instantaneous gamma values within scene exposure density range further lying entirely within a range of values subtended by an angle of 14.degree. measured from a reference point at 0.0 scene exposure density and a viewed reproduction density gradient of A, wherein A is 1.0 in the case of direct view reflection media reproduction, 1.1 in the case of self-illuminated reproduction for viewing with ambient surround, and 1.3 in the case of a reproduction for viewing with dark surround;
• and
• (b) the reproduction has color enhancement wherein a Macbeth Color Checker, if captured in the original scene, would appear in the reproduced image so that (1) the CIELAB chroma ratio is greater than 1/A for at least one of the six high chroma patches (the row above the grey scale), and (2) either the CIELAB chroma ratio for the light skin patch is between 0.8/A and 1.4/A or the CIELAB chroma ratio for the dark skin patch is between 1.0/A and 1.8/A, or the CIELAB chroma ratios for both skin patches are within said ranges, wherein A is as defined in (a) above.