Layer Masking Trick


Today’s Question: I was at your presentation at Photoshop World yesterday, and was hoping you could help me with a detail I missed in my notes. You were working on a photo of a monkey, creating a layer mask for just the monkey. You showed how painting with a normal brush would damage the fur, but I missed the “trick” for how to change the brush to help protect the fur while you were painting. Could you remind me?

Tim’s Quick Answer: The “trick” I demonstrated yesterday involved the use of the Overlay blend mode when painting with black or white on a layer mask. This allows you to gradually build up a lightening or darkening, helping to reduce the risk of painting completely over fine details.

More Detail: The example in this case involved the creation of a selection for a furry animal (a macaque in this case). Because the fur is a bit translucent, it can be difficult to create a good selection. In this type of situation, I’ll often simply create an initial layer mask based on the initial selection. Viewing that layer mask directly (by holding the Alt key on Windows or the Option key on Macintosh while clicking on the thumbnail for the layer mask on the Layers panel), you are able to see the specific details of the mask, including gray areas that should be black or white.

Using the Brush tool, you can set the colors to the defaults of white and black by pressing “D” on the keyboard, and switch between white and black as needed by pressing “X” on the keyboard.

The trick in this case is to also change the blend mode for the Brush tool from Normal to Overlay, using the Mode popup on the Options bar. This allows you to effectively dodge and burn on the layer mask, rather than simply painting with black and white.

With this technique, it is still possible to harm the detail in the image, such as the fur in this case. However, it will generally require multiple brush strokes to eliminate those details altogether. So with a little bit of careful painting you can clean up details around the edge of the object defined by your layer mask (and within the edges of that object) without having a significant impact on the details of the edge of that object.