The great thing about Photoshop is that there is a hundred different ways to accomplish the same task. Here is another way of adding shadows, but a bit more advanced:
Step 1: create a New Effect Layer (step 6 above) and make a layer mask of the area you want to work on by using the selection tools.
Step 2: copy the entire background layer, move the new layer (background copy) above the Effects layer. Desaturate the layer, and change the Blend Mode
to “Overlay”. (these methods were all covered in the post above)
Step 3: Create a “Clipping Mask”. What this does is makes the current layer visible ONLY in the same places that the layer below it is visible. In our case, the layer mask on the New Effect Layer is what controls the transparency of both these layers.
I’ve condensed these three steps into one image:
Here is the result of the clipping mask. Note that the thumbnail now has a little arrow pointing down at the layer below it (the layer that it is clipped to).
Step 4: Adjust the Levels. This time though, I used an Adjustment Layer.
A box will pop up where you can change the name of the Adjustment Layer, and where you can choose to use the layer below it as a Clipping Mask.
Using the Levels box is the same as before. The difference, however, is that it will affect all the layers that it is clipped to (in this case, both the Background Copy and the New Effect Layer).
The advantage of using a layer for your adjustments is that any changes you make can be undone at any time. You can also go back into the Levels dialog box and make more adjustments at any time (just double click on the layer thumbnail). You can mask parts of the adjustment layer by clicking on the Mask thumbnail (then painting or erasing).