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Get Great Black & White Shots Every Time - 12/8/08

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Customize with Channel Mixer for Grayscale Conversions

This Article Features Photo Zoom

Converting color photos to black & white is a tricky proposition. On one hand, it’s one of the easiest one-click changes to accomplish in Photoshop: Image>Mode>Grayscale. Done. Now you’ve got a black & white version of your previously color photo.

The problem with this, and just about any other one-click method, is that the results are as rudimentary as the process. All too often a grayscale conversion leaves a photo looking muddy, flat and boring. The problem is that in the good ol’ days of black & white film, black &white photos were much more than color images with the color removed. Different films and lens filters allowed some colors to pass through, emphasizing the drama in a red flower or the vibrancy of a blue sky—even if the shot was made with black & white film.

Ultimately the tones in a film-based black & white shot aren’t tied exclusively to their colored tonalities; neither should digital black and white be. Ever since the first image was scanned into the computer, photographers have been struggling with converting their color pictures to beautiful black and white.

There’s a conversion option for every mood, and another for every hour of the day. All methods take the information from color channels in an RGB image and render them into grayscale. The best approaches, though, allow photographers to control exactly where and how much each color, or channel, influences the black & white result. It’s like shooting in black & white, but being able to filter the shot after the exposure is made. The original, fully controllable conversion method is the Photoshop Channel Mixer.

In Photoshop’s Image menu, choose Adjustments and then open the Channel Mixer controls. Check the Monochrome box at the bottom of the window, and you’ll see a basic grayscale conversion. Then, keep in mind which channels contain the information you want to emphasize, adjust the sliders to change the grayscale output of the image. You’ll notice first option defaulted to +100, with the other two sliders at zero. While you can adjust the values of each channel well into positive and negative territory of the spectrum, try to aim for a combined total value of all channels at approximately +100. Too little and the black & white image will be underexposed; too much and the image will be blown out. The Constant slider also controls overall brightness, and can be used to compensate for totals on the color sliders as they vary from +100.

If and when you arrive at a setting that creates a great result, you can save that particular combination and load it later for processing additional images. If they’re not of the same tonal values as the original those later images may not be perfect, but at least the saved setting should provide a good starting point—particularly when applied to similar subjects and lighting situations.

And if you’d like a little more understanding of exactly how those three different channels value the colors in a grayscale image, before you ever make a single grayscale adjustment you can see it for yourself in the Channels palette. Click on an individual red, green or blue channel to see exactly how those colors are “filtered” by the RGB color space. It may help to provide a better understanding about how color images can better become black and white, and how you can do that well with the Channel Mixer.

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