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Adjusting Tone Curves

In Develop mode, the Tone Curves tool changes the tonal range of an image. Channel Filtering embedded in the Tone Curves group adjusts either the entire range of the image (RGB), or specific colors (Red, Green, and Blue).

Save adjusted settings as a preset for future use.

Changes made with the Tone Curves tool in Develop mode are non-destructive, which are good creative edits. For pixel-based changes, use the Tone Curves filter in Edit mode.

To adjust the Brightness Curves in an image:

In Develop mode, in the Develop Tools pane, select the Tune tab.
In the Tone Curves group, adjust the curves as described below.

Right-click the number field or the arrow for Blacks, Midtones, or Whites to reset it to the default setting. Double-click the number field or on the arrows to use automatic settings.

Tone Curves Options

Curve	Select a curve to apply to an image. "Standard" curve is the default. Use "Camera" to use the curve generated by ACDSee Professional to produce a curve suitable for the image. The Curve drop-down list is only available for RAW files.
Channel	Specify the color channels to adjust.
Histogram	Displays a graphic of the color information levels in the image, based on the selected channel. Click and drag the line to manipulate the curve. Note that when a point on the curve is clicked, a Node Info Box appears in the top left corner of the Histogram. The Node Info Box contains In and Out pixel values which are set in blocks of color to give a visual representation. The Node Info Box numbers convey that an In value pixel will be changed to the Out value. For example, if the In value is 40 and the Out value is 80, all pixels with a value of 40 will be changed to 80. Clicking the curve adds a new point to the curve. Drag the points up and down the curve. To delete a point, right-click the node and select Delete point.
Blacks	Click and drag the black triangle, or click it, to automatically set the black point, enter a number into the fields, or use the up or down arrow buttons to set an exact black point.
Midtones	Click and drag the gray triangle, or click it, to automatically set the midtone point, enter a number into the fields, or use the up or down arrow buttons to set an exact midtone point.
Whites	Click and drag the white triangle or click it, to automatically set the white point, enter a number into the fields, or use the up or down arrow buttons to set an exact white point.
Auto	Automatically sets the points for blacks, midtones, and whites.
Color Picker	Drag the cursor onto the image to change the cursor to a color picker that provides the RGB and luminance values of the picker's current location. Click the image at a desired tone to add a corresponding point to the adjustment curve.