Apply curves adjustments
You can use the Curves adjustment to adjust the brightness and contrast in a photo. You can adjust the overall look of the photo, change the look of specific colors (red, green, and blue), and adjust settings for the black point, midtones, and white point.
The Curves adjustment shows a histogram with a diagonal line going from the black point (bottom-left corner) up to the white point (upper-right corner). To adjust the brightness or contrast in a photo, you can add points along the line at specific places where you want to change the photo. Drag a point up to increase the brightness; drag the point down to decrease brightness. Drag a point left to increase the contrast at that point; drag it to the right to decrease contrast.
Double-click a photo, then click Edit in the toolbar.
Click Adjust in the toolbar.
In the Adjust pane, click the disclosure triangle next to Curves.
Do any of the following:
Automatically correct the curves of a photo: Click the pop-up menu under the Curves icon, choose RGB or the color you want to auto correct, then click Auto.
Manually set the black point, midtones, or white point of the histogram: Click the Eyedropper button for the point setting you want to change, then click a location in the photo that best represents the black point, midtone, or white point of the photo.
Black point: Adjusts the point at which black areas become completely black (no detail can be seen).
Midtones: Adjusts the lightness or darkness of midtone areas of the photo.
White point: Adjusts the point at which white areas are completely white.
You can also drag the top or bottom handle of the diagonal line in the histogram to change the black point and white point range of adjustment. For example, to adjust the white point of the histogram, drag the top handle to a new location.
Manually adjust the color curves of a photo: Click the Add Points button, then click locations on the photo that you want to change. Each click adds a point to the histogram’s diagonal line. You can also click along the diagonal line in the histogram to add points. After adding points, drag the points to adjust the brightness and contrast in the photo.
Change the red, green, or blue colors in a photo: Click the pop-up menu under the Curves icon, then choose the color you want to change. Click the Add Points button and click locations in the photo that you want to change. Drag the points added to the diagonal line to adjust that color in the photo.