Fine-Tuning Color Selections

In the previous chapter we saw how we can use the Magic Wand tool for making color-based selections. Sometimes there's a better way.

Using Color Range to Make Complex Color-based Selections

Color Range is actually a Selection tool, but I've included it in the Channels chapter because you're better equipped to use Color Range effectively once you understand how channels work. The Color Range feature uses a channels-like interface to show you which pixels are selected and which pixels are protected. It allows you to create a more sophisticated mask than you could achieve with the Magic Wand tool.

Like the Magic Wand tool, Color Range makes selections based on the similarity of color values; its selections are noncontiguous. But the Color Range preview window gives a better indication of which pixels will be selected than the simple marching ants outline that results from a Magic Wand selection. And whereas the Magic Wand tool either selects or does not select a pixel, Color Range allows you to partially select pixelsjust like painting on a mask with gray.

Color Range is the Swiss Army knife of selection tools. In addition to making selections by sampling colors with the eyedroppers, you can also make selections based on specific colors or tonal ranges or out-of-gamut colors. This is especially useful if you are working with an image where you want to change the hue of a particular color, affect only the shadows or only the highlights, or desaturate out-of-gamut colors to bring them back into the range of printable colors.

Choose Select > Color Range and click with the eyedropper on the pixels you want to select. To extend the range of colors, select the plus eyedropper (or hold down Shift), and click in the preview area or image. To remove colors, select the minus eyedropper (or hold Option/Alt), and click in the preview area or image. When the Selection button is checked, your selection is previewed in the Color Range dialog box like a grayscale alpha channel. While I've never found any reason to change this, you can, if you wish, see your selection preview in the image window and choose from the Selection Preview drop down menu to view the selection as Grayscale, against a black or white matte, or as a Quick Mask. The Fuzziness slider is roughly equivalent to the Magic Wand's Tolerance setting but allows pixels to be partially selected. Move the slider to the right to increase the size of the selection.

Note that you might get better results if you first make a rough selection before choosing Color Range.

Figure 2.19. The Color Range tool. Selected areas of the image appear in white, masked areas in black, partially selected areas in gray.

Figure 2.20. Click with the eyedropper on the image to sample the pixels you want to select. Use the plus eyedropper to extend the selection, the minus eyedropper to remove pixels from the selection. Move the Fuzziness slider to the right to expand the selection or to the left to shrink the selection.

Figure 2.21. The resulting selection as represented by marching ants (example A), and after smoothing by 2 pixels and cleanup with the Lasso tool (example B).

Figure 2.22. You can use Color Range to select more than just sampled colors.

Color Range Versus the Magic Wand

This image of Delicate Arch was shot with low light and scanned from a transparency on a midrange slide scanner. Consequently, there's a lot of grain, especially in the Blue channel, which, not surprisingly, is showing up most in the sky. I want to mask the sky so that I can make a tonal correction on the foreground. I also want to sharpen just the foreground so that I don't accentuate any of the graininess in the sky.

Figure 2.23. The original image (example A) and the image edited using a mask to selective sharpen and improve the tonal range (example B).

1.	Open the Arches image. Figure 2.24. Using the Magic Wand for this kind of selection yields a very raggedy selection.
2.	Choose Select > Color Range. To see a selection take shape in the Color Range dialog box, I prefer the Color Range previews set to Selection and Selection Preview set to None. Click with the eyedropper on an area of sky in the image; these areas will become white in the preview to indicate they are selected. Shift-click on any areas of sky that were not included in the initial selection. Dragging the Fuzziness slider up and down will expand or shrink the selectionI used a Fuzziness of about 70. When you have a goodnot perfectseparation between sky and foreground, click OK. Marching ants will appear on the image.
3.	Click the Save Selection as Channel button at the bottom of the Channels palette to save your selection as a channel. What's most important is that there is a separation between what you want selected and what you want to protect. If your selection is the opposite of what you want, either Invert the channel (Image > Adjustments > Invert or Command/Ctrl-I) or, if the selection is active, make an inverse of the selection by choosing Select > Inverse or Command/Ctrl-Shift-I.
4.	Press Command/Ctrl-4 to view just your alpha channel. In this grayscale view, we can clearly see problems with the mask that don't show up in the marching ants view. We can paint on the alpha channel in this grayscale view to fix the problems.
5.	Clean up the mask, starting with the Lasso tool; then use a brush and the Levels command. I used the Lasso to circle the speckly areas and fill them with black or white. I stayed well away from the edges when doing this. With the worst problems fixed, I switched to a hard-edge brush (to avoid introducing any feathering into my mask at this point) and painted out any remaining speckles, again keeping away from the edges. Then I used Levels (Command/Ctrl-L) and moved the black and white input sliders towards the center to make any dark grays in the mask turn to black and any light grays turn to white. Figure 2.25. The channel made from the Color Range selection. Figure 2.26. Using the Lasso tool to select areas and fill them with black or white. Figure 2.27. Using Levels to turn any grays to black or white. Figure 2.28. The cleaned-up mask.
6.	When you have cleaned up the alpha channel, return to the composite channel (Command/Ctrl-~) to complete your refinements. Load the alpha channel as a selection by Command/Ctrl-clicking its thumbnail in the Channels palette. To soften the edges, I applied a Gaussian Blur of 0.5 pixels (Filter > Blur > Gaussian Blur). With a good selection, the world is your proverbial oyster. I chose a Curves adjustment layer with which to make a tonal adjustment and then, on a copy of Background layer, I applied sharpening to the selected area.