face, the blue channel is the one you want. Otherwise, to avoid unflattering shots, steer clear of this channel when converting portraits to black and white (which is discussed in the later section 'Converting an image to black and white using the three channels').
Figure 6–9 shows you how each channel affects an image that contains elements that are predominantly red, green, and blue. The red channel emphasizes the red glow coming from inside the tent, and it shows a very dark sky. The green channel emphasizes the green grass and shows a normal representation of the sky and the light within the tent. The blue channel shows a bright sky and the darkest representation of the tent's interior.
Color representation of the channels combined
Red channel
Green channel
Blue channel
Figure 6–9: Looking at how red, green, and blue are represented in each channel.
Exposing your photo for black and white
When you approach a scene with the intentions of photographing it for black and white, the most important thing to consider is how you'll expose it. After all, most normal situations contain too much contrast for your digital sensor to record a perfect reading. The difference in brightness in the shadows and highlights is too great for each to be exposed properly.
To solve this problem, expose for your highlights and process for your shadows. Be careful not to overexpose the highlights in your scene to the point that they have no detail, however. (Chapter 3 covers how to set your exposures and check them, using the tools provided by your camera.) If you lose the detail in your highlights, you can't bring it back in postproduction. You're more likely to be able to brighten your shadow areas in postproduction.
Your camera likely provides an exposure-warning feature that causes the image on your LCD display to flash when you've experienced a loss of detail. If you receive this warning, decrease your exposure and take another shot to ensure you have detail in your highlights. See your owner's manual to find out more about this feature.
When you expose a scene for its highlights, your original image probably will have very dark shadows. These dark shadows are fine if you feel they serve your message appropriately. However, if you want to create a black and white image that has a smooth gradation of contrast from black to white, with everything in-between, you most likely have to do some postproduction work to get it there, including brightening the shadows.
Figure 6-10 shows a tonal scale that represents the shades that make up a full-scale, black-and-white photo. When you produce an image that contains each of the shades shown, you're on par with Ansel Adams as far as creating a true black-and-white photo. The scale ranges from white without detail to black without detail. The shades in between include whites with detail (or texture), light gray, middle gray, dark gray, and blacks with detail. If you can't see the surface texture of snow in an image, you have white without detail. By having the slightest amount of texture present, you have white with detail.
Figure 6-10: A full-scale, black-and-white image contains each of these tones.
The point in trying to create full-scale black-and-white images is to avoid creating an image that's a muddy, gray mess. Contrast in an image enables viewers to better see what's happening in the scene and makes the overall image look nicer.
Keep the tonal scale from Figure 6-10 in mind when you're exposing an image. Besides representing how much detail is in an image, these tones also help you understand your camera's histogram. Chapter 3 explains how to read the histogram and how to control your exposure.
Converting an image to black and White using the three channels
Because shooting in color with your digital camera produces three black-and-white versions of an image, you really don't need to shoot in black-and-white mode. Doing so gives you less control over your final results. Instead, you can use the three channels I describe in the earlier section 'Being aware of how your digital sensor sees light' to mix and match the channel percentages to create a combination that suits a specific scenario.
You can do this conversion in most photo-editing software programs. Adobe Photoshop is the most common program, so I show you how to convert with it here. Follow these steps to convert a color image to black and white while maintaining control over each element in your scene:
1. Open your image in Photoshop so it contains all its original color data.
Don't convert the image to grayscale. Doing so provides a black-and-white image but eliminates the color information, making all three channels the same. Because of this loss of color information, you lose the benefits of working with these channels.
2. From the layers palette, open a new Channel Mixer layer.
A window opens and enables you to make adjustments to convert your image to black and white. It contains three separate sliders that allow you to adjust the red, green, and blue channels. For more information on working with layers read Chapter 18.
3. Click the box labeled 'Monochrome.'
The image is now black and white.
4. Use the sliders to adjust the percentages of each channel to control how that channel affects your overall image.
When you begin, your red and green channels are each set to 40 percent, and your blue channel is set to 20 percent. They, of course, add up to 100 percent, which represents the normal exposure for the original image you took. So, if you want to emphasize the red light in your scene, set the red channel to 100 percent and the others to 0.
You can create a curves layer to tweak your contrast even more. Chapter 18 gives you the scoop on using curves to adjust contrast in a scene.
Figure 6-11 shows two versions of the same image. The original was exposed properly but needed some work to reach its potential. I converted the first image straight to black and white without making any other changes. The red and green channels were set to 40 percent, and the blue was set to 20 percent.
Figure 6-11: Postproduction work enabled me to increase the contrast in this image and avoid a muddy composition.
I converted the second image more carefully to concentrate on specific elements. Consider the following changes:
Bringing the red channel to 65 percent brightened the tonality of the woman's skin.
Dialing back the green to 25 percent gave the grass more brightness. (Grass usually comes out as yellow in an image and is affected by the red channel as well as the green channel.)
Reducing the blue channel to 10 percent minimized the texture of the woman's skin.
After I converted the image, I used the Curves Layers feature in Photoshop to further increase the contrast and make the whites and blacks in the image richer. (Check out Chapter 18 for more about using this feature.) The result is a more descriptive photograph that's more pleasing to look at.
Color or Black and White — How your Decision Impacts your Message
