Getting Exact with Advanced Masking Techniques in Photoshop

Layer masks are tremendously useful, and if you’re like me, you’ll find yourself addicted to them. They can be fantastic for blending layers and making multiple images dissolve into one another. Vector masks create shapes defined by vector paths and produce clean, smooth-edged graphic elements. Channel masks are probably the most time-consuming of the masking lot, but they’re powerful and accurate. Like anything in life, the more you practice using them, the faster and better you get.

Working with Layer Masks
Like any other mask, a layer mask is a grayscale image that you can edit to your heart’s content. Layer masks are excellent for blending layers of images together and creating soft transitions between elements. For versatility, layer masks are unparalleled. They allow you to gradually brush in transparency and opacity on a selective pixel basis. Paint with black to hide portions of the layer; paint with white to display portions; and paint in varying shades of gray to partially show elements. You can even apply gradients, image adjustments, and filters to your layer masks to create interesting special effects. After you get the concept of layer masks, you’ll never use the eraser tools (covered in Book VI, Chapter 2) again. You won’t have to because one of the great things about layer masks is that
you can forever edit, or even delete them, with no permanent harm whatsoever to the image.

Creating layer masks
To create a layer mask, select your desired layer and choose Layer-->Add Layer Mask-->Reveal All or Hide All.
- Reveal All creates a mask filled with white, which shows the layer.
- Hide All creates a mask filled with black, which hides, or masks, the layer and shows nothing but transparency.
You can also click the Add Layer Mask icon at the bottom of Layers palette (which by default selects Reveal All). You can’t add a layer mask to a background layer. You must convert the background layer to a regular layer if you want to use a layer mask on the background of an image. You can also apply a layer mask. Choose your desired layer and make a selection using one of the selection tools. Choose Layer-->Add Layer Mask-->Reveal Selection or Hide Selection. You can also click on the New Layer Mask button in the Layers palette to create a mask that reveals the selection. After you create the layer mask, you can grab the painting tool of your choice and apply your grayscale color. Remember: Add white to the mask to display the image. Add black to hide the image. Add gray to make the image semi-transparent.

Using the Gradient and Brush tools on a Layer Mask
I must confess: I use two of the layer masking tools more than the others:
- The Gradient tool, set to a linear gradient of black to white or white to black is truly awesome. Simply drag the layer mask to create the gradient. The darker areas of the gradient gradually hide the image, whereas the lighter areas gradually show the image.
- The Brush tool, with a large, feathered tip, using the Airbrush option and the Flow set to around 10% is amazing. With these settings in place, you can create feathered edges that blend one layer into another without any harsh lines. I started with the black-to-white linear gradient, which I dragged from the left edge of my image through to the right edge. I then took the Brush tool with a large feathered tip (265 pixels), selected the Airbrush option, set the Flow to 10%, and worked my way around the profile of the girl’s face to get rid of some more of the background behind her.

To edit a layer mask, click the layer mask thumbnail in the Layers palette. Select your desired painting or editing tool, and paint or edit the mask to perfection. Just be sure that you’re working on the layer mask, instead of editing the image itself. Otherwise, you’ll apply paint directly to your image. You can tell because you’ll see a layer mask icon next to the eye icon in the Layers palette.

Managing layer masks
Here are some tips to help you work with your layer masks. You can do the following:
- Load a layer mask: Loading a layer mask means getting a selection outline based on the layer mask. Simply Ctrl+click (Ô+click on the Mac) the layer mask thumbnail.
- View the mask without viewing the image: Sometimes when you’re editing a layer mask, you may find it helpful to see the mask itself without having to view the image, too. Simply Alt+click (Option+click on the Mac) the layer mask thumbnail to view the mask and hide the image on the layer. To redisplay the image, Alt+click (Option+click on the Mac) again or click the eye icon in the far left column.
- View the layer mask as a red overlay: If you prefer to see your layer mask as a red overlay (called a rubylith), Alt+Shift+click (Option+Shift+click on the Mac) the layer mask thumbnail.
- Click again with the same keys to remove the overlay: You can change the opacity and color of the overlay in the Layer Mask Display Options dialog box, which you access by double-clicking the layer mask channel in the Channels palette.
- Paste a copied selection into a layer mask: Simply Alt+click (Option+click on the Mac) the layer mask thumbnail. Choose Edit-->Paste and then Select-->Deselect. Click the image thumbnail in the Layers palette to return to the image. The copied selection can consist of anything, but this technique comes in particularly handy when you’re copying one layer mask into another.
- Disable (temporarily hide) or enable a layer mask: Just Shift+click the layer mask thumbnail or choose Layer-->Disable Layer Mask or Enable Layer Mask.
- Unlink a layer from its layer mask: By default, Photoshop links a layer mask to the contents of the layer. This allows them to move together. To unlink a layer from its layer mask, click the link icon in the Layers palette. Click again to re-establish the link.
- Discard a layer mask: Just drag the layer mask thumbnail to the trash can icon in the Layers palette. Click Discard in the dialog box. Or you can choose Layer-->Remove Layer Mask-->Discard.
- Apply a layer mask: When you apply a layer mask, you fuse the mask to the image. Photoshop replaces all black areas in the mask with transparent pixels and all gray areas with partially transparent pixels; all white areas are image pixels. Drag the thumbnail to the trash can icon in the Layers palette. Click Apply in the dialog box. Or you can choose Layer-->Remove Layer Mask-->Apply.