Descriptions of Calculate blending options
You can select various blending
methods in the Calculate Image
dialog box.
Normal. Places Source 1 over
Source 2 at the specified opaci-
ty. 100 percent opacity replaces
Source 2 with Source 1.
Multiply. Creates a darker
channel than the source chan-
nels. Black areas in either source
create black areas in the result-
ing channel. White areas do not
affect the result.
Screen. Creates a lighter chan-
nel than the source channels.
White areas in either source cre-
ate white areas in the resulting
channel. Black areas do not
affect the result.
Overlay. Places Source 1 over
Source 2 without destroying the
shadows or highlights of Source
2.
Soft Light. Lightens or darkens
pixels in Source 2 depending on
the brightness value of the cor-
responding pixels in Source 1.
Pixels in Source 1 that are light-
er than 50% black lighten
Source 2. Pixels in Source 1 that
are darker than 50% black dark-
en Source 2.
Hard Light. Lightens or darkens
pixels in Source 2 depending on
the brightness value of the cor-
responding pixels in Source 1.
Hard Light works similarly to
Soft Light. However, black in
Source 1 produces black in the
resulting channel and white pro-
duces white.
Darken. Replaces pixels in
Source 2 with the correspond-
ing pixels in Source 1, if the pix-
els in Source 1 are darker.
Lighten. Replaces pixels in
Source 2 with the correspond-
ing pixels in Source 1, if the pix-
els in Source 1 are lighter.
Add. Creates a lighter channel
than the source channels. Add
is similar to Screen but usually
produces a higher-contrast
image.
If you select the Add option,
you can enter a Scale value
from 1 to 2 with a precision of
three decimal places. To calcu-
late the average brightness val-
ue of two channels, choose Add
and enter a Scale of 2.
You can brighten or darken the
resulting channel by specifying
an Offset value. To lighten the
overall image, enter an offset
from 1 to 255. To darken the
image, enter an offset from -1
to -255.
Subtract. Creates a darker
channel than the source chan-
nels. Subtract is similar to Multi-
ply. However, corresponding
pixels of the same color pro-
duce black in the resulting chan-
nel.
If you select the Subtract
option, you can enter a Scale
value from 1 to 2 with a preci-
sion of three decimal places.
You can brighten or darken the
resulting channel by specifying
an Offset value. To lighten the
overall image, enter an offset
from 1 to 255. To darken the
image, enter an offset from -1
to -255.
Difference. Compares the color
value of each pixel in Source 1
with the corresponding pixel in
Source 2, subtracts the darker
value from the lighter, and then
uses this difference in the result-
ing channel.