Digital Outback Photo
- Photography using Digital SLRs


The Art of Digital B/W #004


Simulating B/W filters in Channel Mixer

note by Thomas Niemann


November 2004 "Digital Fine Art Photographer's Summit" in Phoenix, AZ

Photographers often utilize filters to enhance their black & white photography. When converting color images to black & white you can simulate filters in Photoshop. Consider the following picture of the Ickworth House.

Channel Mixer
Yellow Filter
Orange Filter
Red Filter
Green Filter
Dreamy Infrared

Grayscale is the Photoshop Image > Mode > Grayscale command. Other effects were done in the Channel Mixer, with Monochrome enabled, using the following settings. For Dreamy Infrared, first use the Channel Mixer to convert to Infrared, duplicate the layer (Ctrl-J), apply a gaussian blur, and specify Overlay for blending mode. For less contrast vary opacity and experiment with Soft Light and Luminosity.

Filter    R/G/B
none   40/30/30
yellow   60/28/12
orange   78/22/0
red   90/10/0
green   10/70/20
infrared   40/140/-80

Note the values for each filter add to 100. You can manually enter these values in the Channel Mixer dialog box, or download Actions from ePaperPress that allow you to simulate a filter with a single click. For some insight in the workings of the Channel Mixer, let's examine each color channel individually.

Red Green Blue

The red channel is sensitive to red light, and least sensitive to blue light. Note the light roses and a dark sky. The green channel lightens shrubbery and grass, while the blue channel lightens the sky. You can obtain a similar effect using black & white film and shooting through colored filters.

If you design your own settings mix at least two channels to avoid excessive noise. If the results seem a bit wimpy after conversion try increasing contrast with a Curves adjustment layer and applying an S-shaped curve.


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