Many digital cameras and scanners let you capture images in grayscale. However, you can often get better results by starting from a color image and converting to grayscale in Photoshop. This is because some hues are darker than others at the same level of saturation (for example, the most saturated yellow is much lighter than the most saturated red). Whenever you have an image in which color helps define the subject, try one of the techniques that let you customize the conversion to grayscale, so that the existing color relationship is translated into a similar tonal relationship.
Using Black & White
The Black & White feature lets you control how colors translate into tones in a way similar to how film photographers place colored filters in front of their lenses to control contrast in the resulting black-and-white image.
Black & White is available as a dialog (Image > Adjustments > Black & White), but it's best to use it as an adjustment layer (through the Adjustments panel). You can open the Adjustments panel and click the Black & White button, or use any of the other methods that you've used to add an adjustment layer. In Black & White ( Figure 11-1), each of the color sliders determines how dark each color appears in the grayscale image. For example, to deepen a blue sky, drag the Blues slider to the left to darken the blues in the grayscale image. By altering the relationships of colors to tones in Black & White, you can often arrive at more satisfying grayscale conversions in less time than if you had simply converted to grayscale and adjusted tones using curves, masks, and blending modes. You may still need to use those tools, but probably just for fine-tuning and special cases. If you are after a certain look, try the Black & White presets in the Adjustments panel—they include settings that emulate effects traditionally produced using color filters with black-and-white film, along with a simulation of infrared rendering. Use the Tint sliders to apply color effects such as sepia tones.
Figure 11-1 The Black & White adjustment
If you're working with a raw digital camera file, you may prefer to perform the grayscale conversion using the HSL/Grayscale tab in Adobe Camera Raw (see Chapter 5, "Building a Digital Workflow") because it's earlier in the workflow and doesn't require saving a much larger Photoshop file and adjustment layer. On the other hand, if you want the original raw file to maintain its color conversion settings, or if the image needs additional edits that can't be done in Camera Raw, it makes sense to use Black & White in Photoshop. The controls are similar in both places.
Black & White includes the On-Image Adjustment tool discussed in Chapter 7, and it's stupendously intuitive here. When it's selected, you don't even have to use the sliders. Position the On-Image Adjustment tool over the tone of the image you want to darken or lighten, drag right to lighten or left to darken, and Black & White automatically changes the color value for the tone you drag.