You can manually adjust the brightness and contrast of an image using the Brightness/Contrast command. This is one of the simplest of the lightness correction commands.
Important: To apply this command to a selection, the image must be a 16 million (24-bit) color image (otherwise the command is applied to the entire image). In addition, adjustment layers are available for 16 million (24-bit) color or greyscale images only. To increase the color depth of an image, see Increasing the Color Depth of an Image.
To adjust contrast and brightness manually:
To limit the adjustment to a specific area, make a selection in the image. See Using the Selection Tools.
Do one of the following:
To modify the image pixels directly, choose Adjust > Brightness and Contrast > Brightness/Contrast.
To create an adjustment layer, choose Layers > New Adjustment Layer > Brightness/Contrast. For information on adjustment layers, see Using Adjustment Layers.
In the Brightness edit box, select a negative number to darken the image or select a positive number to lighten image. A value of zero indicates no change.
In the Contrast edit box, select a positive number to increase the contrast or select a negative number to decrease the contrast. A value of zero indicates no change.
Click OK.
Adjusting Individual Brightness Values
Adjusting the Brightness and Contrast in Unison
Adjusting the Brightness of the Highlights, Midtones, and Shadows
Adjusting the Lightness Levels
Correcting Images by Adjusting the Histogram