Generating the Masks
The first thing we need to do is to decide what kind of localized changes we need to apply to our picture. Before we start, keep in mind that in Lightroom, the masks you create actually define the areas that will be modified, rather than the areas that are left unchanged. For this image, I wanted to brighten up the water as a way of bringing more contrast to the silhouetted lighthouse, and I also wanted to make the yellow-orange colors in the sky a little more punchy and interesting without going overboard. This will also create color contrasts between the warm sky and the surrounding blue clouds and water (Figure 2).
Figure 2: Our demo image has some nice colors and contrast points, but it could be enhanced by working on areas like the water and the yellow-orange clouds.
Personally, I find it’s easiest to work with Lightroom’s masks if I can see them by default. To set this up, go to the toolbar at the bottom of the Lightroom window and check the “Show Selected Mask Overlay” option (Figure 3). This way, each time you create a new mask and begin to paint it onto your preview, you will see the red overlay, allowing you to make corrections as you go.
Figure 3: Turn on the Show Selected Mask Overlay option before you start creating your masks.
Next, turn on the “Auto Mask” under the Brush Flow option, near the bottom of the Adjustment Brush panel. This will allow Lightroom to help you detect medium and high contrast edges as you brush the mask across the preview. Though it doesn’t always detect all edges with precision, it will eliminate many unwanted overlaps and re-dos. Finally, set your Brush Size and Feather amounts to values that make the brush easy to see at the magnification you’re working with, then move the cursor over your target area and click once to set the mask “Pin” (a silver dot with a black center when it is selected).
Now you can brush out a mask region just as you would in Adobe Photoshop. The masked areas will show up as a transparent red overlay. If you still end up overlapping areas you didn’t intend to mask, hold down the Option/Alt key, and you should see the brush cursor display a minus sign (-) at its center. Once you see that, brush the edge of the overlapping areas. When you’re finished you should have a mask with well-defined boundaries like the one shown below in Figure 4.
Figure 4: Lightroom 4’s Adjustment Brush makes it easy to create well-defined masks on your image preview. These masks define your editing regions.