by Julieanne Kost
A great way to ensure that a change you make to an image is only affecting the tonal (not color) values is to set the blend mode to Luminosity. For example, if you have an area in an image that is too dark and you want to lighten it without changing the colors, add a Curves Adjustment Layer and set the blend mode to Luminosity. Then raise or lower the curve as necessary – without affecting the color values. This can be especially helpful when dodging or burning skin-tones. If you want to affect the colors and not the tonal values, simply change the blend mode to color.