Create a Transparent Shadow
Use Gaussian Blur to create a soft-edged shadow against a graduated background.
Create the Shadow
Creating a soft-edged effect using Gaussian Blur is as easy to do in Illustrator as it is in Photoshop—well, almost. In this example we’ll add a soft-edged shadow under the taxi.
Create a rectangle to use as the shape of the shadow. Cut the shadow rectangle (Cmd [Ctrl]-X), then select the blue gradient background and press Cmd (Ctrl)-F to paste the shadow in front. Round the edges of the rectangle to make the corners softer by selecting the shadow rectangle and choosing Filter > Stylize > Round Corners. When the Round Corners dialog box appears enter 5 pt and click OK A.
Use Gaussian Blur
With the shadow still selected, choose Effect > Blur > Gaussian Blur A. In the dialog box enter 3 for the pixel radius B. You’ve just created a beautiful softedged shadow that blends perfectly into the background—but there’s one big, fat caveat! . . .
Photoshop Effects = Resolution
When you chose the Gaussian Blur effect, you might not have noticed that the effect was in the Photoshop Effects category A. Using Photoshop Effects requires that you think in pixels, not in vectors. Your first clue should have been when you entered a value in pixels, not in points or inches, in the Gaussian Blur dialog box. Since Illustrator is a vector-based application, you usually don’t have to worry about resolution, but since Gaussian Blur is a pixel-based filter, just as in Photoshop, you need to make sure that the resolution (the number of pixels in your file) is correct for the final output of your file.
Zooming in you’ll see that the beautiful soft-edged shadow is actually very pixilated B—just like the pixilation that occurs when you zoom in on a 72 pixels per inch (ppi), or computer screen resolution, file in Photoshop. Because the effect is pixel-based and the resolution is set by default to 72 ppi (see “Caution: 72 dpi by Default”), the soft edge will only look good at 100 percent on your computer screen or on the Web.
Select Effect > Document Raster Effects Settings C and in the dialog box that appears change the resolution to 300 ppi and click OK D. Since the resolution is now set higher, and there are 300 pixels per inch instead of 72, the 3-pixel blur distance we originally specified is much narrower than we would like E.
With the shadow selected, go to the Appearance palette and double-click the Gaussian Blur layer to bring up the Gaussian Blur dialog box again F.
This time enter 10 for the pixel radius. Click OK and you’ll see that the shadow looks great again and that setting the resolution when using Photoshop Effects can make a big difference G.