LCH

LCH - A color model that describes color in terms of Luminance, Chroma, and Hue.
Lightness - See luminance.

LCH stands for Luminance, Chrominance and Hue, which are three of each image's basic characteristics, affecting the viewer's perception of color.

The LCH curve for the above
If you want to experiment, the Photo Effects tool also lets you create sepia and other toned black and white effects. Pretty nice, really. You can use this not only for raw (NEF) files, but also for 16-bit tiff files.

This tool can help to keep you from making minor visual color correction errors due to monitor calibration errors or mild color blindness. This tool can also provide tonal values in CMY, CMYK, LAB HSL, LCH and K ...

See also: Image, Light, Color, Digital, Hue