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Chapter Four. Camera Raw Controls > The Tone Curve Panel

The Tone Curve Panel

The Tone Curve panel (which you access by pressing Command-Option-2) is the first panel with two faces: the Parametric Curve Editor and the Point Curve Editor (see Figure 4-10). Why two curve editors? The parametric curve editing was introduced in Lightroom, and in order to maintain cross-compatibility, it was also incorporated into Camera Raw 4. For some functions, such as relatively simple contrast adjustments, either can be used. Their capabilities are similar but their usability is vastly different. In actual use, the Parametric Curve Editor offers a quicker means of achieving a desired tone mapping, whereas the Point Curve Editor can help you obtain a more accurate placement of a curve. Your choice should be predicated on the precision your image needs versus the ease of accomplishing what you need. Both require practice.

Figure 4-10. The two faces of the Tone Curve panel


Parametric. The Parametric Curve Editor uses a simplified user interface to allow quicker adjustments of the Highlights, Lights, Darks, and Shadows. The effectiveness is further enhanced by the range adjustment slider underneath the curve plot, which is used to expand or contract the range over which the curve adjustments are applied. The Highlights control the one-quarter tones and white; the Lights control the one-quarter tones; the Darks control the three-quarter tones; and the Shadows control the three-quarter tones and black. Neither black nor white are affected—those points remain the domain of Exposure and Blacks for setting clipping points. The up and down arrow keys change the units in increments of 1; adding Shift changes the units in increments of 10.

 

The plot of the luminance image data is in the background, although it’s in a different scale than Camera Raw’s main color histogram.

Point. While the Parametric Curve Editor can often produce the right tone curves more quickly, there’s no denying that the Point Curve Editor can accomplish far finer-tuned controls—particularly in the data rich areas of extreme highlights. The curve behaves like Photoshop CS3’s refined curves adjustment. Moving a point will have an impact on the other side of the next point. To place very fine point curves, you can simply click on the curve to add a point; to delete a point, just drag it off the curve plot.

Tip

One obscure function of the Point Curve Editor is the ability to see, on the curve, exactly where the cursor is hovering when you hold down the Command (Mac) or Ctrl (Windows) key. If you click on the image holding the key, you can actually place a point on the curve. This is useful when you zoom in to work on delicate highlights that may need special treatment to tease tone values apart to maintain textural detail.


The input/output readout is based on your current working space settings. The up and down arrows and right and left keys change the units in increments of 1. Adding Shift changes the units in increments of 10.

You can choose different hard-coded curve presets from the dropdown menu, but there is no function that lets you save or delete using the menu. You can save a new custom preset for just curves separated by parametric or point curves and apply presets in this manner.

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