Curves Adjustment Using Locking Points

I often want to make small adjustments to a particular range of tones in a part of an image - usually to increase the contrast between these tones, but I don't want to change most of the adjacent tones. This can be done easily by "locking" the adjacent tones first, before making the curves adjustment.

Create a new Curves adjustment layer - the curve you create will affect the entire image, but focus just on the part of the image that interests you and we can localize the effect of the curve later.

With the curves dialog open, click and drag the mouse around on the various parts of the image - a tone point will move on the curve in the dialog to display the various tones for these parts of the image.

In this example, I want to add some contrast to the clouds, but I want to preserve all of the other tones in the image. The clouds have most of their tones around the J4 tones of the image.

For tones in the image that you do not wish to change, Ctrl /ftiij+click on these tones to create "lock" points on the curve; these points will remain unchanged. Repeat to cover all the tones that you wish to protect. These lock points on the curve will assure that these values will be unchanged by this curve adjustment. In this example, I place lock points on the dark hills and the bright open area in the sky.

Now you can go to the tones that you wish to change and Ctrl /B'Sj+click to

Drag the mouse pointer over the image, a tone point on the curve will show the tones for the pixels under the pointer
/ + click on tones in the image that you want to prevent from changing. This creates points on the curve that will not be moved.

I / click on the image to make a point on the curve and adjust the point to edit the tones for this point create a point within these tones but now go ahead and move the point on the curve to change the tones. This can be done easily using the arrow keys. Typically, I just experiment by moving the adjustment point around to increase the local contrast.

Hit OK to close the curves dialog.

You may now wish to localize the effect of this curve to only a certain area of the image. Do this by painting on the mask for the curve adjustment layer.

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