Friday, December 17, 2010

The science of lightness perception - part 4

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.

Illuminance: also called illumination, illuminance is the total perceived amount of light falling on a surface (incident light).

Illuminance edge: an actual edge in an image that is revealed by a change in illumination.

Intrinsic image: reflectance images and illuminance images - together these two types make up the luminance image seen by the retina of the eye and the camera sensor.

Lightness: perceived reflectance.

Luminance: also called intensity - luminance is the combined emission of illuminance (incident light) and reflectance (reflected light) from diffuse surfaces.

Luminosity: also called brightness, luminosity is the subjective quality of luminance as processed and perceived by the visual cortex of the brain.

Percept: an individual's visual experience of something external to themselves.

To be continued ...


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