Basic Photoshop Skills – Layer Masks

I used to consider the use of Layer Masks in Photoshop to be an advanced technique, but it has become such a commonplace and important part of post-processing photos, that I now think of it as a basic skill that all Photoshop users need to have in their arsenals. It can seem a little confusing at first, but once you understand how it works it is really quite simple and powerful.

Basically a layer mask lets you cover up part of a layer in Photoshop to reveal what is in the underlying layers.  You can have two layers with different content that you can blend together, or two layers with the same content processed differently that you want to combine, but with only selected portions of each layer.  For this example, I am using the same image on both layers, but with one layer in color and the other in black and white. You can accomplish the same goal by using just the color version of the image and adding a black and white layer adjustment. Either way, the process of editing with a layer mask is the same.

The full color version of the image.

Starting with a color image, I duplicate the image so that I have two layers with identical content.  I then converted the top layer to black and white.  When I do this, the black and white image is all you see because it is the top layer.  I then add a layer mask to this top layer by clicking on the layer mask icon at the bottom of the layers palette (it looks like a gray rectangle with a circle cut out of the center.)

adding a layer mask

To add a layer mask to a pixel layer, click on the layer mask icon. (Adjustment layers come with a layer mask automatically.)

Once a layer mask is added to a layer, all you need to do is paint on the image with black to reveal the bottom layer.  I like to use the paint brush tool to add the black, using a brush with a hardness of 0, feathering the mask so that it’s easier to get the edges of the mask to look seamless (you also need to make sure your foreground color is set to black since the brush will paint with whatever foreground color you have set.) With this image, wherever I paint with black, the color image underneath will be revealed.

Black and White photo with Color Flowers made using a layer mask in Photoshop.

Here’s the result of combining a color and black and white version of the same image, using a layer mask to paint away the black and white layer, revealing the color layer underneath only on the bouquet of wildflowers.

The beauty of a layer mask is that you can easily tweak it.  In this case, I accidentally painted over part of the girl’s jacket, revealing the blue on the color image.  To fix this, all I needed to do was change my foreground color to white and paint the mask back on.  You can use more than the paint brush tool as well – basically adding black to the mask in any manner will reveal the layer underneath.  For example, I could have created a selection of just the sky and then filled that selection with black.  Also, you can use varying shades of gray to change the strength of the mask (basically blending the top layer with the bottom layer wherever you paint.)  You can also do this using the opacity and flow settings in the paint brush tool bar.

Adding an adjustment layer.

For this example, I actually went through one step more than was necessary by duplicating the original layer and converting it to black and white.  Instead, I could have used a layer adjustment to make my black and white conversion. One of the great features of adjustment layers is that they are automatically created with a layer mask.

To create a layer adjustment, click on the layer adjustment icon at the bottom of the layers palette or click directly on the adjustment in the adjustments palette.

The great part of using the adjustment layer method for making this change is that in addition to being able to adjust my layer mask at any time, I can also go back and tweak my black and white conversion at any time by double clicking on the adjustment icon on my adjustment layer.  And of course, you can use a layer mask on any type of adjustment layer, giving you a lot of power to fine tune your images.

If you’re looking for a workshop that covers post-processing skills like this while getting the chance to shoot in some beautiful locations check out my July Acadia workshop or my September Cape Cod workshop.

Leave a comment below if you have any questions about this technique or if you have suggestions for a future post.



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