Giving Flat Art Highlights and Shadows with Alpha Channels

Sometimes you need to give your art — whether it’s a photo or another type of image — a little shine and shadow to bring it to life. You can do this by creating and saving your selections as alpha channels and filling them with translucent color. The great thing about alpha channels is that because you save them with your document, you can use them time and time again. Just follow these steps:
1. Create a simple piece of artwork to use as a basis for your shadows and highlights.
I created a pool ball by creating two layers.
- On each layer, I used the Elliptical Marquee tool to create differentsized circles.
- I filled each of the circles with a separate color.
2. Choose Window➪Channels.
The Channels palette appears. Be sure to keep this palette visible because you will be creating some new channels for the highlights.
3. Choose the Pen tool from the Toolbox (also known as the Tools palette) and create a path for the highlight.
I created a path for the highlight on the top-left portion of the ball in my example, assuming that the light source is coming from the upper-left corner..
4. Choose Window➪Paths.
The Paths palette appears.
5. Click the third icon from the left at the bottom of the Paths palette.
You see your work path disappear and a selection marquee appear.
6. Choose Select➪Save Selection.
The Save Selection dialog box appears.
7. Name the channel. Make sure the channel is new and click OK.
An additional channel appears in the Channels palette. This new channel is the alpha channel —your saved selection.
8. Click the New Layer icon in the Layers palette. Double-click the layer name and rename it.
I named mine “large highlight.” It’s important to put your highlights and shadows on separate layers so that you can apply different opacity settings and also retain the ability to tweak them later if needed.
9. Choose Edit-->Fill, choose the White option for Contents, and leave all the other options at their default settings. Click OK.
The dialog box closes. Your highlight is now filled with white. Don’t worry; it won’t stay this opaque.
10. In the Layers palette, adjust the Opacity setting to 50%.
The highlight should now appear translucent.
11. Choose the Pen tool and create a path for the highlight on the bottom of the object.
Make sure the path matches up to the edge of the object. Use the Direct Selection tool if you need to adjust the anchor points or curve segments of the path.
12. In the Paths palette, click the third icon from the left at the bottom of the palette.
The work path disappears, and a selection marquee appears.
13. Choose Select-->Save Selection. In the Save Selection dialog box, name the channel. Make sure the channel is new and click OK.
Mine is called “bottom highlight.” Another alpha channel appears in the Channels palette.
14. Repeat Steps 8, 9, and 10, but only adjust the Opacity to 30%.
15. Use the Pen tool to create a path for the smaller shadow.
For example, I created a path on the bottom right of the ball.
16. Load the path as a selection in the Paths palette and choose Select-->Feather. Enter 3 pixels and click OK.
The idea is to give the shadow a softer edge.
17. Repeat Steps 6 through 10, but fill the selection with black instead of white and adjust the opacity to 20%.
18. Use a selection tool to add a cast shadow.
In my example, I used the Ellipse tool, pressed Alt (Option on the Mac), and created an ellipse at the base of the ball.
Then I feathered the selection 25 pixels before I saved the selection. The cast shadow needs to have really fuzzy edges, thus the large number of pixels for the feather.
19. Repeat Steps 8 and 9, filling the selection with black.
My highlighted and shadowed pool ball is ready to roll. If your cast shadow layer is above your object, you have to change the stacking order and move your shadow layer so that it’s below your object. Now that you’ve spent all this time on the front end creating your alpha channels, you can then save time on the back end by using those alpha channels to apply highlights and shadows to similar artwork.
20. To load alpha channels, choose Select-->Load Selection and select your alpha channels from the Channel pop-up menu. Then repeat these steps.
In my example, I took the highlights and shadows I created with lucky pool ball number 7 and loaded them as alpha channels in pool ball number 5.