No need for antialiasing when the edges of your selection are perfectly vertical and perfectly horizontal. Any deviation from 0°, 90°, 180° or 270°even if only a small amount should have antialiasing applied.
Unless you specifically WANT the jaggedy stairstepped look, you should use antialiasing for any selection that has rounded or diagonal edges.
Antialiasing is a method to recreate a shape at a higher resolution as a bitmap, then downsample it, say 4 times, so each screen pixel corresponds to 16 enlarged pixels (4 times 4). 16 black pixels become one black pixel. 16 white pixels become one white pixel. 16 pixels that are a mix of black and white become a corresponding shade of gray.
Antialiasing works on text — so long as yuou are using an outline font, paths, oval marquees, and the lasoo tool. A magic wand selection of an antialiased area with antialiasing on will simulate antialiasing by partially selecting the shaded pixels at the edge of the selection.
Don’t get this confused with feathering which allows width variance of anti-aliasing either starting from the middle of an edge and expanding outward equally on either side or from one side inward.
Feathering actully has nothing to do with antialiasing, and does not care if your selection was antialiased.
Think of a selection as a grayscale image (that’s what it is). Feathering is identical to blurring that image.
Where is feathering terminology used in the tools of PS? Is it used in the Marque and Magic Wand tools? Where did I see where you could actually set the amount of pixels to feather from the edge of the selection? I’m probably getting confused in the terminology.
You can have a selection make with the lasoo or marquee feathered by changing the tool options. You can also feather any selection with Select->Feather.
I like to work in the mask, by pressing Q to swith to quickmask. There, I can blur my selection selectively, feathering just the parts I want. Press Q to return to select mode and I’m in business.
Great tip, Scott, thanks.
Yeah, Quickmask is Photoshop’s best kept secret.
