Thursday, December 16, 2010

The science of lightness perception - part 3

In continuing to set the stage for my review of the new PercepTool2, and realising that many don't yet have George DeWolfe's Book, B&W Printing, I'm going to present some of George's glossary terms in this and the next few posts.

George notes that many of the words that he uses have additional meanings in other contexts, but are used here as they relate to the science of lightness perception. I'll present the basic information. Readers are encouraged to get George's book in order to dive into the details.

Fundamental error: the fundamental error in lightness perception is that objects on dark backgrounds appear lighter and objects on light backgrounds appear darker.

Gamut compression: a perceptual compression of the grayscale that occurs when the range of luminance values is greater than a 1:30 highlight to shadow ratio.

Gamut expansion: a perceptual broadening of the grayscale that occurs when the range of luminance values within a framework is greater than a 1:30 highlight to shadow ratio.

Gestalt principles of visual organization: proximity, similarity, closure, continuation, and belongingness.

Grouping: refers to the grouping of certain visual attributes such as tonal values, edges, depth boundaries, corners, and the Gestalt principles of visual organization in a local framework.

To be continued ...

Enjoy.

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