Adobe ILLUSTRATOR CS2 User Manual page 252

ADOBE ILLUSTRATOR CS2 245
User Guide
Selecting the Knockout Group option cycles it through three states: on (check mark), off (no mark), and neutral
(square). Use the neutral option when you want to group artwork without interfering with the knockout behavior
determined by the enclosing layer or group. Use the off option when you want to ensure that a layer or a group of
transparent objects will never knock each other out.
See also
"About the Transparency palette" on page 243
"About targeting" on page 420
"Printing and exporting transparent artwork" on page 484
About opacity masks
An opacity mask uses a masking object to alter the transparency of the underlying artwork. Where the mask is white,
the artwork is fully visible. Where the mask is black, the artwork is hidden. Shades of gray in the mask result in
varying degrees of transparency in the artwork.
A B C D
Creating an opacity mask
A. Underlying objects B. Object with blending mode and transparency C. Object filled with black-to-white gradient D. C moved over the
area of B and masking B
Once the opacity mask is created, a thumbnail of the masking object appears in the Transparency palette to the right
of the thumbnail of the masked artwork. (If these thumbnails aren't visible, choose Show Thumbnails from the
palette menu.) By default, masked artwork and masking object are linked (as shown by a link between the thumb­
nails in the palette). When you move masked artwork, the masking object moves along with it. However, when you
move a masking object, the masked artwork doesn't move. You can unlink the mask in the Transparency palette to
lock the mask in place and move the masked artwork independent of it.
Transparency palette displays opacity mask thumbnails: left thumbnail represents masked objects, right thumbnail represents masking objects
You can move masks between Photoshop and Illustrator. Opacity masks in Illustrator convert to layer masks in
Photoshop, and vice versa.
See also
"Printing and exporting transparent artwork" on page 484