Most teeth, by design, have a slight yellow cast. Add coffee, wine, tobacco, and a host of staining foods, and the smile isn't quite as bright as it could be. In everyday life, this isn't a major issue. But for special portraits, a warm, inviting smile is important. This Photoshop hack is so easy, you'll wonder why you never figured it out before. As long as you show a little restraint with the technique, the results look quite natural.

First, open your portrait in any version of Photoshop. I'll use Photoshop Elements for this illuminating exercise. Use your favorite tool to select the teeth. I usually start with the Magic Wand. Click on a middle-toned tooth with the wand and see what it selects. By holding down the Shift key, you can make another selection to add to the first one. At this point, I switch to the Lasso tool to clean things up. You can add to the existing selection by holding down the Shift key and lassoing more areas. Or, by holding down the Option key, you can deselect areas that you don't want affected by the upcoming adjustments.

Now it's time to remove some of that natural yellow tint. In Photoshop Elements, open the Hue/Saturation dialog box (Enhance→Adjust Color→Hue/Saturation). The path is a little different in Photoshop CS (Image→Adjustments→Hue/Saturation). Choose the Yellow channel from the Edit drop-down menu and move the indicator on the Saturation slider bar to the left, as shown in . This will desaturate the Yellow channel—or, in English, get rid of the stain.

I've found that setting the Yellow channel to somewhere between -70 and -80 does the trick nicely. Once you've toned down the yellow, select Edit→Master and move the indicator on the Lightness slider bar to the right, as shown in . As you move the indicator to the right, you're brightening the teeth. Be careful with this adjustment, however, because you can overdo it and create an unnatural, super-bright smile.

Click OK to exit the Hue/Saturation dialog box and review your handiwork. You might want to hide the selection marker (known by Photoshop pros as the marching ants) to get a better look at the adjustment. Just press Ctrl-H or choose View→Selection. If you need to make further adjustments, reopen Hue/Saturation and give it another go.

Once the smile is clean and bright, deselect the teeth by choosing Select→Deselect. Then, use Save As to give the file a new name. You never know when you might want to go back to the original portrait, so keep it in a safe place.

Remember, the best corrections are the ones that look natural.