Luminous Colors
By John Bates
1 December 2007
Ever since the introduction of inexpensive color film, the central, defining argument in photography has been: color, or black and white? (Well, maybe not the central, defining argument. But gosh-darn it, people do get het up about it.) The truth is, any time that you show one of your color pictures to somebody, they really see two pictures: the color one, and a black and white one. By realizing that, you can use digital processing techniques to make *both* of the pictures that they see say what you want them to say.
What do I mean when I say that a viewer sees two pictures? When the human brain takes images from the eyes, they are processed down multiple pathways. Color information and black and white information (called luminosity) is split apart, munged and mangled, and somehow wind up getting merged back together. Practically, this means that shape and shading are the "first" things that a viewer reacts to. (Of course, the entire process is actually much more complicated and cognitive than simple pipelines of images. But for the purposes of this article, pretend that what I'm saying is the simple truth.)
My first exposure to black and white photography came in a high school darkroom, where I learned the arcane arts of dodging, burning, and masking. (I also learned not to leave my fingertips dipped in the fixer, but that's a different story.) Fast forward twenty years, and I'm re-learning the same techniques in the digital age. Making a good black and white digital image involves the same set of goals: evening out the tonality, emphasizing the areas you want the viewer to focus on, de-emphasizing the areas you want them to ignore, and making the right details *pop*.
The real magic of digital black-and-white, though, I found by accident. After spending hours working an image until I had the tones, shapes and details *just right*, I used Photoshop to put the original colors of the photograph back in place. Suddenly, subtly, the color picture was improved. The colors seemed to flow, and all of the black and white work that I'd done was still serving its purpose, emphasizing all the right details. Since then, I've integrated a luminosity step into almost all of my post-processing.
It's remarkably easy to make simple improvements in color images this way. If you're using Photoshop CS3, there's even a simple filter layer that makes it a two-step process. After you've done all of your sharpening and color correction, just add a "Black & White..." filter layer at the top of your stack, adjust the conversion until you have the most pleasing black and white image you can get, and then change the blending mode of that layer to "Luminosity..." (all the way down at the bottom of the menu). You'll probably be astonished at the result. And since it's a filter layer, you can go back and tweak the conversion parameters, and directly observe the changes that your black and white image makes to your color one.
Of course, there are limitations. Changing a very dark area to a very light one, or vice versa, will give you unnatural colors. Making an area too bright will probably clip and distort the original's colors. But generally, even dramatic changes in the tone of a black and white image will lead to very subtle and pleasing color images.
The "Black & White..." layer is just the simplest approach. You can use any conversion technique you'd like to get the most pleasing black and white image, copy that back into a new layer in the original, and change its blending mode to luminosity. Personally, I like to work though an image in LAB mode, dodge and burn (using soft light blending, not the dodge and burn tools), and then pop back into RGB for the final processing. But any approach that gives you a better black and white interpretation will give you a better color one, too.
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