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panel. However, if you check the ‘Channel Overlays’ option, this allows you to toggle seeing the individual color channel curves as you edit the main composite channel curve (as seen in Figure 5.29). The Histogram box allows you to toggle displaying the ‘cached’ histogram within the grid area, while checking the ‘Baseline’ option allows you to toggle displaying the standard reference line to compare your curve movements against. Lastly, the ‘Intersection Line’ option allows you to toggle temporarily displaying the intersection lines seen as you mouse down on a curves point. This feature is also on by default in the Adjustment panel and is there is so that you can more easily reference a curve point against the outline of the histogram.

Figure 5.29 -clicking anywhere inside the grid area allows you to switch the grid units from 25% (Light) to 10% (Pigment/Ink) increments.

Saving and loading curves

Curve settings can be saved by going to the Curves options menu (circled in Figure 5.30) and selecting the ‘Save Preset…’ option. Once you have named and saved a setting, the preset will then be accessible via the Presets list menu that appears at the top of both types of Curves dialogs. To delete a preset, make it active then go to the Curves options menu and select ‘Delete Current Preset’.

Figure 5.30 You can save any Curves adjustment as a custom preset by choosing ‘Save Preset…’ from the Curves menu (circled). This pops the Save dialog shown here. Once a Curves setting has been saved, it will appear listed in the Curves preset file list (you can save a Curves setting wherever you like, but it will only remain in the Presets list if you keep it stored in the default Curves folder). Pre-existing Curves settings can be added by going to the same menu and choosing ‘Load Preset…’. Note: a Curves setting must include the. csv extension for without it you cannot load it back into Curves.

Using Curves in place of Levels

You can adjust the shadow and highlight levels in Curves in exactly the same way as you would using Levels. For example, in the Curves adjustment dialogs you have the Input shadows and Input highlights sliders and you can drag these inwards to clip the shadow and highlight levels (Figure 5.31). In Levels you alter the relative brightness of the image by adjusting the gamma slider, while in the Curves adjustment you can add a single curves point and move it left to lighten or right to darken.

Threshold mode preview

The Curves input sliders work exactly like the ones found in Levels. You can preview the shadow and highlight clipping by holding down the key as you drag on the shadow and highlight sliders circled in the Curves dialog shown in Figures 5.31 and 5.32.

Figure 5.31 The Levels and Curves panel settings shown here can both be used to apply identical adjustments to an image. In the Levels adjustment example I moved the shadows and highlight Input levels sliders inwards. You will notice that the Curves adjustment has an identical pair of sliders with which you can map the shadow and highlight input levels. In the Levels adjustment you will notice how I moved the Gamma slider to the right, to darken the midtones. In the Curves adjustment one can add a point midway along the curve and drag this to the right to achieve an identical kind of ‘Gamma’ midtone adjustment.

Output levels adjustments

If you select a shadow or highlight curves point and move it up or down, you can adjust the output levels for the shadows or highlights. Figure 5.32 shows how to apply equivalent tone adjustments to the output levels in Levels and Curves, while Figure 5.33 shows some further examples of where the output levels have been adjusted.

Figure 5.32 The Levels and Curves settings shown here will also apply identical adjustments. In the Levels adjustment I kept the input levels the same and adjusted the output levels to produce an image where the optimized levels were mapped to a levels range of 20–210. In the Curves dialog you can see the highlight point is selected and the curve point has been