Image Optimization Using Tone Curves

You can further refine the tonal range of your image using the Tone Curve ¬°jjj tool (figure 5-45, page 165). ACR offers a choice of Parametric and Point curves. Point curves can be adjusted using presets from the tool's menu or manually, the same way we do when we are using the Photoshop Curves tool (figure 5-44). We often use the default Medium Contrast preset or select the Linear preset if we want to make additional corrections later in Photoshop.

The point curve tool is more powerful than the parametric curve, and you can even use negative gradients to produce tone inversions. But be careful as it is very easy to skew colors using curves. For this reason, we usually limit ourselves to using the parametric curve (if we use curves at all).

In our crab image, we use the Highlights slider to brighten the image slightly. Additionally, we shift the right-hand marker (located beneath the curve display) slightly to the right to limit the range of values the change is applied to. This makes the ice in our image slightly brighter. The triangular markers beneath the display also limit the range of values the Highlights, Lights, Darks, and Shadows sliders affect.

We can now return to the Basic tab to make our final adjustments to the Contrast and Clarity values.

Figure 5-45: Brightening the highlights within a narrow range using the Parametric curve tool
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