The Advantage Of Photo Filter Adjustment Layers
One of the most brilliant things Adobe did when they added Photo Filters to Photoshop (these filters replicate the old traditional screw-on lens filters) was to make them adjustment layers. You can create one by clicking on the Create New Adjustment Layer pop-up menu in the Layers palette and choosing Photo Filter. After you apply a Photo Filter from the resulting dialog (let’s say, for example, you used Warming Filter 81 to warm a cool photo), you can get the Brush tool (B), set your Foreground color to black, and paint over any areas of the photo you don’t want to be warmed. This gives you a level of flexibility you wouldn’t get any other way.