Maximizing and minimizing bright areas in an image
You can increase or decrease light areas in an image with the Maxi-
mum and Minimum filters. The Maximum filter adds light to shad-
ows. The Minimum filter shrinks light areas.
When you apply these filters, Canvas compares each pixel to its
neighbors within the radius you specify, then replaces it with the
lightest or darkest pixel in the group.
Isolating images with the
High Pass filter
1 With an image in edit mode,
choose Image > Select > All.
Then choose Edit > Copy.
2 Choose Image > Show
Channels.
3 Create a new alpha channel
by clicking the button in the
lower-left corner of the
Channels palette.
4 Select the new alpha chan-
nel and choose Edit > Paste.
5 Choose Image > Filter >
Other > High Pass and enter
a radius value. Click OK.
6 Choose Image > Adjust >
Threshold. Adjust the thresh-
old until you outline the ar-
eas you want. Click OK.
7 Paint areas white to include
them in the selection. Fill the
rest of the image with black.
8 Click the composite channel.
Choose Image > Select >
Load to load the alpha chan-
nel and select an area.
9 In the example, the final im-
age was finished by choos-
ing Image > Select > Load
with Inverse selected.
10 Then, choose Image >
Filter > Blur > Gaussian Blur
to apply a Gaussian blur of
3.0 pixels.
Original Image
High Pass filter
Threshold filter
Editing with Paint
tools
Finished alpha
channel
Isolated subject
Tip
To apply a choke or spread to
an image manually, use the
Maximum or Minimum filters in
a color channel.
Original
Maximum 6 pixels
Minimum 6 pixels