Photoshop Mask

PhotoShop has a masking feature called Quick Mask that is different
from layer masks. See the next page for more information on Quick Mask.

Create a layer mask
You cannot add a mask to the background layer. I will usually duplicate
the background layer and then fill my background layer with a background
color, often white. The illustration at the left shows a simple setup
for preparing to add a layer.






There are two methods to add a layer mask. You can choose Layer >
Add Layer Mask > Hide All or Reveal All. Hide all fills the layer
mask with Black, masking the entire layer. Reveal All fills the layer
mask with white, or applying no mask to the layer.

You
can also choose the Add Layer Mask Icon from the bottom of the Layers
window (highlighted with yellow). If you have no active selection, this
choice will produce a mask with white fill, or the same as the Reveal
All menu selection. If you have an active selection, the selection will
be set as white, with the rest of the layer mask filled with black,
or masked.

The sample at the left shows both the original photo, and then a Reveal
All mask added to the layer. Note there is no change to the photo. In
this sample, the mask edit mode is on, as shown by the closest icon
to the layer thumbnails. With this icon showing, any edits we do will
be applied to the mask, not the photo. If the edit mask icon is not
showing, click on the mask thumbnail in the layer row to activate it.



Edit the Mask
When the mask edit mode is activated, the foreground and background
colors automatically change to black and white. If you choose another
color as the background or foreground color, your choice is automatically
converted to the grayscale equivalent. Again, keep in mind that this
does nothing to your original photo – the grayscale restriction
is only for the mask.


As a simple exercise, let's add a mask to make the border pixels mask
the photo with 50% transparency. Select All. Choose Select> Transform
Selection and holding your ALT (Option) key to resize your selection
from the center, set the size of your borders. Unless your image is
square, you may want to move the sides independently from the top and
bottom for an even border. Double click to set transformation. Choose
Select>Inverse to select the border pixels.

Choose Edit>Fill from the main menu and specify Black and 50% for
Blending Opacity. In the sample at the left, note how the selection
borders are reflecting the change to the mask, and therefore the photo,
but the photo remains untouched (see the thumbnail). The mask now has
a 50% gray border. This is masking the photo by 50% and allowing 50%
of the background, or white, to show through. If
we change the background to brown and make no changes to the photo layer,
the results will be as shown here. Since the mask is working on the
photo layer, the 50% border will allow whatever is on the lower layer
to show through.

This is quite powerful, but you really could do this with the selection
tools. Squares and straight lines are great for learning about masks,
but let's evoke a little more mask power. We are going to use painting
tools to make the border more interesting.



Adding paint effects to a layer mask
I changed the background back to white for easy visibility. Activate
the mask edit icon by clicking on the mask in the layer window if necessary.


This effect started with a wide border selection. Create a layer mask
as above. Activate mask edit mode and fill selected area with a pattern
fill. This creates a rectangular
frame with the pattern texture allowing some of the background to show
through.


To
create the irregular edges, select the Pattern Stamp Tool from the Rubber
Stamp tool fly-out. With mask edit activated, click along the edges
of the frame to create an irregular edge. The Pattern Stamp Tool paints
with the current pattern fill. You can see the effect of the new edges
in the layer window sample shown above the photo.


You can also apply filters or any other paint tool to
a mask. The effects are limited only by your imagination. The best way
to actually become comfortable with masks is to play. If you can find
an hour or two to experiment without production pressure, you will have
your time back many times over in the future. Masks are great tools
for automation and consistency in addition to the wealth of artistic
opportunities they present.