Tone Curve Adjustments
The Tone Curve header uses "regions" of adjustments relating to highlights, lights, darks, and shadows (see Figure 8). When you use a control slider to make adjustments to one of the four regions, an odd-shaped balloon appears to identify the region of adjustment. When you push the sliders left or right, the highlighted region curve takes on a new shape based on how far to the left or right the control slider is moved.
Unlike Photoshop's tone curve, which doesn't have any limits to the shape of the curve, Lightroom's balloon within the tone curve creates a limit for the adjustments. This is actually a good thing, because it prevents the image from becoming overly processed when exported from Lightroom. Besides using the control sliders, the tone curve can be manipulated directly by inserting the mouse pointer on a region of the curve and holding the mouse button down as you push up or down on the curve. One more method of adjustment for the tone curve is to enable the target mode in the upper-left corner of the panel. Place the mouse pointer directly on the image, hold down the mouse button, and move the mouse pointer up or down to affect the region on the tone curve directly. How cool is that? This targeted adjustment isn't just limited to the tone curve, but applies to hue, saturation, luminance, and gray.
Figure 8 Tone curve adjustments have regions relating to highlights, lights, darks, and shadows. These balloon-shaped regions represent the limits of adjustment with the tone curve.
The Tone Curve panel also offers some preset point-curve contrast adjustments for linear contrast, medium contrast, and strong contrast in the pull-down menu at the bottom of the adjustment panel. These preset point curves are great for enhancing image tone. My approach is to use one of the preset curves as a starting point and then continue to adjust the regions to enhance the image further. In Figure 9, for example, the strong contrast curve was used by pushing down on the shadow adjustment and up on the highlight adjustment, rendering the image with a bit more contrast and saturation.
Figure 9 The Before and After view of the Tone Curve adjustment uses the point curve to adjust the curve manually, by pushing the shadows down and highlights up. Creating a steeper curve helps to enhance the contrast.