Layer Masks

Using Layer Masks

Photoshop CS2 allows you to mask selected areas of a layer. Masking gives you the ability to hide, edit, and protect, selected areas of an image. Further, masking allows you to blend, merge, and add fade attributes to multiple images within the same document. This document will define the two types of layer masks available in Photoshop CS2, it will detail the necessary steps to add a mask to a selected area of a layer, and it will explain how to hide and reveal portions of a layer within another layer.

Masks

In Photoshop CS2 there are two types of mask available, the layer mask and the vector mask. Both of these masks are grayscale images; meaning, you should cover a selected area in black that you would wish to hide and anything you would want to be partially visible you would paint using various shades of gray. The lighter the gray the more transparent the selected area is, white is fully visible. Once you hide part of an image using a mask, you can modify or fully restore it at any time since the mask is just covering up, and has not deleted, that part of the image. This is one of the distinct advantages of masking.

Layer Masks

Layer masks are the most common type of mask used. Layer masks are created by using the Painting Tools, primarily the Brush Tool. The layer masking method will cover a large area of an image quickly. While this method may save time, your masked area is more likely to be imprecise and have uneven edges that are not present with the vector masking method.

Vector Masks

Vector masks will give you a much cleaner and defined looking image than a layer mask will. Vector masks are created by using the Pen, Shape, or Path Selection Tool. While the edges of the mask are more precise, it takes a little more time and precision to create this mask than is necessary with a layer mask.

Creating a Mask

These steps will explain how to add a mask to your image in your Photoshop CS2 document. 
NOTE: Layer masks and vector masks can be applied to the same layer.

Instructions:

Open or create your image(s) in Photoshop CS2

Place the image(s) you wish to add masking properties to in their respective layers 
NOTE: Name each individual layer with a meaningful name. This will allow you to identify the contents of the layer quicker. For more information on naming layers see Renaming Layers.

Select the layer which you wish to apply a mask to

From the bottom of the Layers Palette, click ADD LAYER MASK
A white thumbnail will appear in the Layers palette on your selected layer. This thumbnail will display the masking properties you add to this layer.

From the Toolbox, click the PAINT BRUSH TOOL, if you would like a layer mask 
OR 
Click the PEN, PATH SELECTION, or SHAPE TOOL, if you would like a vector mask.
NOTE: Layers masks consist of only white and black. Therefore, you can only apply the colors white and black to a layer mask with the tools referred to here. To hide areas of a layer you will want to apply black. If later you wish to reveal an area that you have masked, apply white.

Use your desired tool to designate the areas on the image you would like to hide or mask.


When you are finished, the areas that you have masked will be hidden from view. 


Hiding and Revealing Selections

You can use a layer mask to hide or reveal a selected area.

Hiding a Selection

Hiding a selection applies a mask over the selected area; the selection is not visible. The portion of the layer directly beneath the masked layer which corresponds to the selection is now visible. In the Layers palette, the layer which has a hidden selection will display a white thumbnail with the selected area in black. The example below shows a hidden selection along with the Layers palette.

Revealing a Selection

Revealing a selection applies a mask to the area surrounding the selected area; only the selection is visible. The portion of the layer directly beneath the masked layer which corresponds to the area outside of the selection is now visible. In the Layers palette, the layer which has a revealed selection will display a black thumbnail with the selected area in white. The example below shows a selection revealed along with the Layers palette.

To hide or reveal a selection:

Select the layer which you wish to apply a mask to 
NOTE: Any layers above the layer you have selected in the Layers palette will not be effected by the mask.

Using a selection tool, select the portion of the image you wish to hide or reveal


From the Layer menu select » Layer Mask » Hide Selection or Reveal Selection

http://www.uwec.edu/help/PhotoshopCS2/masking.htm

how to make masks in photoshop elements

http://graphicssoft.about.com/od/pselements/qt/layermasks.htm