Figure 7: The Adjustment Brush has all of the controls of the Graduated Filter, plus brush size and feather controls.
For many, many photos, all you'll need to do is use Exposure, but Lightroom 4 offers many other controls, as well. Remember to set Exposure to the right amount for your photo. Clarity can be useful for skies, Sharpness can allow you to affect the sharpness of specific areas, negative Highlights often can be used to get better clouds, and so forth. To set a slider back to its default, double-click the slider itself. If you don't like a particular graduated filter, just press the delete key to remove it. You can add multiple new graduated filters to refine your image as needed. Each filter is represented by a white dot on the picture—click on the dot and it will turn to a black dot, which means you can change any of the adjustments once again.
The Adjustment Brush sits right next to the Graduated Filter in the toolbar below the Histogram and holds all of the adjustment capabilities of the Graduated Filter. Setting its size and edge softness (feather) is key to its use. I rarely use Flow or Density because I like to keep use of the brush simple (Fig. 7). Once you set an adjustment for this tool, you paint the effect onto the picture. If you don't like the look, erase it by using the Erase option for the brush.
Figure 8: Use extreme settings to see the effect.
Once again, set Exposure to an extreme amount so you can see exactly where you're brushing (Fig. 8). Set the brush to a reasonable size for the area you want to work on, and keep Feather at 100 for better blending. It can be helpful to continually change your brush size as you move along edges and into smaller or larger areas. Use the bracket keys on your keyboard to quickly make the brush larger or smaller.
A big problem that I see people consistently having with this in my classes at BetterPhoto.com is edges. If you go too far over an edge where there's a big difference in brightness, you'll start getting a haloing effect along that edge. That affect is very obvious to viewers and will make them question your work. Go back along that edge and use the erase option for the brush to fix it.
Figure 9: A total of six Adjustment Brushes were used on this photo.
Pro Tip: Don't use the Reset button at the bottom of the Adjustment Brush or the Graduated Filter to reset your adjustments for the tool. That reset button gets rid of all of your Graduated Filter or Adjustment Brush work. You can reset any slider by double-clicking on the slider itself, or you can hold down the Alt or Option key and you'll see a new reset button appear at the top of the panel. Click that to reset a single brush or filter application.
Six different Adjustment Brushes were applied to the photo you see here (Fig. 9). The active one shown in this image is removing the green flare at the bottom right with the white balance controls of Temp and Tint. The other brushes used mostly Exposure, with a little bit of Clarity mixed in. The brushes were constantly changed in size to fit the needs of the area being worked on. To do these sort of adjustments with Photoshop would take an inordinate amount of time, which is why many photographers using Photoshop never do them.