New Chromaticity Diagram



Last Update: July 2009              Rhodonine™ and Activa™: See Citation Page

The following figure is presented here at reduced scale (resolution)to accommodate a browser. A version offering greater precision is available in Chapter 17 in the Download Files area reached from the Site navigation bar.

Spectral Threshold @ 600 pixels

Spectral Threshold Function of the Human Visual System under photopic conditions [from Section 17.2.3]

The above figure describes the theoretical spectral threshold performance of the human eye with great precision. The curve describes the measured data of Pitt to a remarkable degree (well within a ± 2 nm envelope) and demonstrates the systematic deviations from a smooth curve in the measured data are not due to measurement technique.

The overall performance is computed from the signal to threshold performance characteristic of the P and Q chrominance channels individually followed by a merging of the curves. As best as can be determined, the merging occurs at a wavelength of 532 nm. The perceptual selection process appears to be based on a a maximum signal to threshold criteria (using absolute values in the above figure).

The above features are discussed in detail in Chapter 17.

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