Using Overlay in Photoshop?

[ethandale]

Hello!

So I've been getting lots of advice from various people about digital art, and the one I hear most is to "use overlay." I know there are both overlay layers, and there's some sort of overlay brush mode. I don't know anything about how the brush part of it works, but here's my understanding of the overlay layer:

The overlay layer affects the layer underneath.

Painting white on the overlay layer causes colors to become brighter, while painting darker causes them to become darker.

However, when I paint white on my overlay layer, it acts as if I'm just painting with a white brush. The predictability of the layer is very low, and it seems to do whatever it wants, whenever it wants. Am I doing something wrong? Does it have to do with the overlay brush mode?

And maybe I'm just bad at google, but I couldn't find hardly any video tutorials on the subject of overlay (especially newer ones for CC). Thanks in advance for the help!

[Norman Sanders]

Brush:

With the Brush Options bar set to Overlay and the Foreground color set to White, the degree of lightening is controlled by the Options bar Opacity setting. You may want to experiment with values below 20% for starters.

With the Brush Options bar set to Overlay and the Foreground color set to Black, the degree of darkening is controlled by the Options bar Opacity setting. You may want to experiment with values below 20% for starters.

Layers:

Brush set to Normal. If you add a blank layer above the image, and then Edit > Fill with 50% gray and Layers Blending Mode set to Overlay, painting in a value low of white will lighten the image a tad at a time, a value of black will darken the image a tad with each dab. Your change may be edited by turning off the eye of the images layer and cloning 50% back into the local area to be returned to its unedited state. 

[Trevor.Dennis]

Clarifying what Norman has said about using the Brush in Overlay mode, you set the mode in the options bar, and not the layers panel

If you copy and paste this example image into Photoshop, and set your brush to Overlay, and try painting with black and white.

You'll find that you can harden up the dark lines and remove the feint lines.  It's a bit like magic, and it is a powerful, and incredibly useful trick to have in your Photoshop box of tricks.

Overlay as a layer blend mode, is often used when applying texture layers.

Using the same pencil drawing and copying the layer, the Overlay blend mode (red highlight) has lightened the image by removing all those tones less than 50%, whereas the layer set to Multiply (green highlight) has reinforced the dark tones.