Specifications

The Digital Fine Print Course
Editing a Fine Print
Altered Luminosity
The luminosity of an image is our perception of the relative lightness and darkness of its
colours. Photoshop’s luminosity formula mixes 30% of the Red channel + 59% of the
Green channel + 11% of the Blue channel to represent the luminosity of the image. In tra-
ditional BW photography contrast filters were used to alter this luminosity rendering. For
example a red filter was used to dramatically darken blue sky and intensify clouds.
Copyright Les Walkling 2012
13/50
Original Image
Original Luminosity
Original Colour plus Altered Luminosity
Photoshop’s Channel Mixer in Monochrome mode can easily create altered luminosity
renderings. In this example, 110% Red + 80% Green + -100% Blue mimics the effect of a
medium red filter. This lightens green foliage while darkening the blue sky and increas-
ing cloud contrast. Blending this Monochrome Channel Mixer adjustment layer on
Luminosity combines its altered luminosity with the original image colour (Hues). The
image’s Saturation is also adjusted by the Luminosity blending mode to maintain, with
varying succes, the overall appearance of the image despite its redistributed luminosity.
Altered Luminosity Rendering