Quick and Dirty Masking in Photoshop

Masking is essentially just another way of making a selection. Instead of defining your selection with a selection outline, masks define your selection with 256 levels of gray, which allows you to have varying levels of selection. Photoshop masks or protects unselected pixels from any commands you execute. Photoshop doesn’t mask selected pixels, making them fair game to any executed commands. There are different types of masks for different purposes — channel masks, layer masks, and vector masks. You can use them to temporarily make a selection, save and load selections, define vector shapes, selectively apply an adjustment layer or filter, blend one layer into another, and so on. This section covers using masks for selection purposes.

Although selecting with the Marquee, Lasso, and Magic Wand tools can be fine, you’ll soon find that these tools have a limited repertoire: You can’t use them with much accuracy on more complex images. Sure, you could break out the Pen tools and for some difficult images they do a superb job — that is, if you can get the hang of drawing Bézier curves. But when you need to play with the big boys, that’s when you turn to masking. Most things that pack a powerful punch are either expensive or hard to master, or both. Well, you already forked out a pretty penny for Photoshop. And yes, masking isn’t for those who get their selections via a drive-thru window.

Working with Quick Masks
As you can probably guess from the name, Quick Masks allow you to create and edit selections quickly without having to bother with the Channels palette. They are also user friendly in that they allow you to see your image while you’re working (typically masking with channels doesn’t). You can begin your Quick Mask by using a selection tool or a painting tool. After you have your Quick Mask, you can edit the mask using any painting or editing tool. Quick Masks are temporary, so if you create one you really like, be sure and choose Select-->Save Selection at the end of the following steps. That way you can save the mask as an alpha channel.

Follow these steps to create your very own Quick Mask:
1. Open a new document and, using any selection tool, select the element you want in your image.
Don’t worry about getting the selection perfect. You’ll be able to fine-tune your selection after you have the Quick Mask in place. Note that you can also just paint your mask from scratch. But I think that starting with a selection is easier.
2. Click the Quick Mask mode button in the Toolbox (also known as the Tools palette).
The Quick Mask mode button is the white circle on a gray square icon. A color overlay covers and protects the area outside the selection. The selected pixels are unprotected.
3. Refine the mask by selecting a painting or editing tool.
Paint with black to add to the mask, thereby making the selection smaller. Paint with white to delete from the mask, making the selection larger. Paint with a shade of gray to partially select the pixels. Partially selected pixels take on a semitransparent look, perfect for feathered edges. You can also apply a filter or adjustment (Image➪Adjustment) to the Quick Mask. Even though the Quick Mask displays a red overlay, you are still working with a grayscale image. If you don’t believe me, pull up the Channels palette and look at the Quick Mask channel.
4. After you finish editing your mask click the Standard mode button (a white circle on a white square icon) in the Toolbox to exit the Quick Mask.
The Standard mode button is just to the left of the Quick Mask mode button. The overlay disappears and a selection outline appears. The selection outline correlates with the unmasked or selected areas of the Quick Mask. Your selection is ready and waiting for your next command.

Changing Quick Mask options

You can change Quick Mask options by doubleclicking the Quick Mask mode button in the Toolbox. When you add a Quick Mask to a selection, by default a red overlay covers the selected area. The overlay has an opacity setting of 50%. In addition to changing the color and opacity of the overlay, you can also choose whether you want the overlay to represent the masked (unselected, protected) areas or the selected (unprotected) areas.