Using Layer Masks in Photoshop

 
Layer masks give you a great amount of selective control over the image.

Layer masks give you a great amount of selective control over the image.

Sarang Naik shows you how to use a layer mask for selective adjustments in Photoshop CS5.

A layer mask is the most powerful tool Photoshop has up its sleeve. Its an absolutely essential tool for both professionals and serious amateurs alike, one that can take your post processing ability up several notches. Still a lot of people are ignorant of this tool, believing that it is difficult to master. Well yes, it does take some time and practice to start using the masks in creative ways, but the basics are really simple! And the basics are all you need to know in the beginning.

So what exactly does a layer mask do? It gives you complete control over an effect (such as contrast, saturation, etc) by letting you decide how much and on what part of the image will the effect be applied. Now you can also control the ‘how much’ by changing the opacity of the layer. But that changes the transparency of the entire layer. What if you want the effect to be seen only in a particular part of the image?

That is where layer masks prove their worth–using a brush, you can paint over a layer mask to reveal the effect only in that part. Sounds tough? It’s not! I’ll show you how to do this in a few simple steps, but before that remember this basic rule of layer masks:

“White Reveals, Black Hides.”

A white layer mask completely reveals the effect of the layer on the image while a black layer mask completely hides it. So to hide a part of the layer,  paint over a white mask with a black brush and to reveal a part of the layer, paint over a black mask with a white brush. So let’s see the steps involved to do this:

1. Open the Image You Wish to Edit
I am using this image of a sunset. I boosted the overall contrast with a basic curves layer. The lower part of the image looked too bland to me so I added another curves layer. But now, the upper part of the image has become too dark for my liking. So I’ll hide the effect in the upper part by using a layer mask.

Adding global contrast to the image made the upper part too dark.

Adding global contrast to the image made the upper part too dark.

 

2. Invert the Layer Mask
You will notice that the curves layer already has a white layer mask assigned to it. The area of the image in which I want to reveal the effect is relatively small. So I’ll hide the effect from the entire image and reveal it where I want by painting over the image. So first let’s invert the layer to hide the effect. Select the white layer mask by clicking on the thumbnail and press Ctrl+I. Now the mask will turn black.

The inverted layer mask (in black).

The inverted layer mask (in black).

 

3. Prepare the Brush Tool
Select the brush tool in the tools panel. At the bottom of that same panel there are two overlapping squares that allow you to choose the foreground and background colours. Since we are painting over a black layer mask, make sure that the foreground colour is white and the background colour is black as shown in the image below.

Selecting the brush and the foreground colour from the tools panel.

Selecting the brush and the foreground colour from the tools panel.

Now at the top of the window, open the drop-down menu for the brush. To make the selection blend in seamlessly with the image, keep the hardness as 0%. From the presets,  select a basic brush with a blurred outline. Don’t worry about the size slider. You can easily change the size of the brush anytime you want by holding down the keys for the square or curly brackets. The [ or { key reduces the brush size while the ] or } key increases it.

Selecting the brush presets.

Selecting the brush presets.

 

4. Paint in the Effect
Now, making sure the layer mask is selected (by clicking on the thumbnail), paint on the lower part of the image and you will see that the contrast is increased only in that part.

The final layer mask.

The final layer mask.

If you want to see the actual layer mask superimposed over the image, then click on the layer mask thumbnail while holding down the Alt key and you will get this: Alt+click on the thumbnail again to get your image back.

Alt+click on the thumbnail to view it big!

Alt+click on the thumbnail to view it big.

Here’s a before and after comparison of the image:

Final

And there you have it! By using a layer mask, we have selectively increased the contrast in parts of the image that needed it while keeping the rest of the image as it is. It is a simple technique but it opens up so many possibilities–you can do selective colouring, exposure blending or give a fake tilt-shift effect using layer masks. Your imagination is the limit.

 

Tags: photoshop, Image editing, post processing, Editing, Digital Post Processing, Sarang Naik, Photoshop CS5, Layer Masking, Layer Mask, Using Layer Masks in Photoshop, selective editing, selective control