• Choose Image > Adjustments > Levels.

• Choose Layer > New Adjustment Layer > Levels. Click OK in the New Layer dialog box.

• Double-click the Set Gray Point Eyedropper tool  in the Levels dialog box to display the Adobe Color Picker. Enter the values you want to assign to the neutral gray, and click OK. Then click in a part of the image that should be neutral gray.

• Click Options in the Levels dialog box. Click the Midtones color swatch to display the Adobe Color Picker. Enter the values you want to assign to the neutral gray, and click OK. This method has the advantage of showing you a preview of the values you’re assigning.

In general, assign equal color component values to achieve a neutral gray. For example, assign equal red, green, and blue values to produce a neutral gray in an RGB image.