Adobe PHOTOSHOP 5.0, User Manual, Page: 283 / 400

275 ADOBE PHOTOSHOP 5.0
User Guide
8
Select Mask if you want to apply the blending
through a mask. Then choose the image and layer
containing the mask. For Channel, you can choose
any color or alpha channel to use as the mask. You
can also use a mask based on the active selection or
the boundaries of the chosen layer (Transparency).
Select Invert to reverse the masked and unmasked
areas of the channel. (See “About masks” on
page 249.)
9
For Result, specify whether to place the
blending results in a new image, or in a new
channel or selection in the active image.
10
Click OK to perform the calculation.
Calculations blending options
The Add and Subtract blending modes are
available only with the Apply Image and Calcula-
tions commands. For a description of the
remaining blending options, see “Selecting a
blending mode” on page 205.
Add
Adds the pixel values in two channels. This is
a good way to combine nonoverlapping images in
two channels.
Because higher pixel values represent lighter
colors, adding channels with overlapping pixels
lightens the image. Black areas in both channels
remain black (0 + 0 = 0). White in either channel
results in white (255 + any value = 255 or greater).
The Add option divides the sum of the pixel values
by the Scale amount and then adds the Offset value
to the sum. For example, if you wanted to find the
average of the pixels in two channels, you would
add them, divide by 2, and enter no Offset value.
The Scale factor may be any number between
1.000 and 2.000. Entering a higher Scale value
darkens the image.
The Offset value lets you lighten or darken the
pixels in the destination channel by any brightness
value b255 and –255. Negative values
darken the image; positive values lighten the
image.
Subtract Subtracts the pixel values in the source
channel from the corresponding pixels in the
target channel. As with the Add option, the result
is then divided by the Scale factor and added to the
Offset value.
The Scale factor may be any number between
1.000 and 2.000. The Offset value lets you lighten
or darken the pixels in the destination channel by
any brightness value b255 and –255.
Creating clipping groups
In a clipping group, the bottommost layer, or base
layer, acts as a mask for the entire group. For
example, you might have a shape on one layer, a
texture on the overlying layer, and some text on the
topmost layer. If you define all three layers as a
clipping group, the texture and the text appear
only through the shape on the base layer and take
on the opacity of the base layer.