Photoshop has some amazing tools. But sometimes, the tools need work-arounds for their effects to be realistic in the natural world. This tutorial shows one such work-around - to create a partial shadow; that is, when only part of an object (in this case, the fingers of a hand) casts a shadow on another object (in this case, a bucket of apples). Photoshop Drop Shadow layer effect would ordinarily add a shadow to the entire hand, which is not realistic.

You can apply this technique to any Photoshop Effect that needs to be trimmed or constrained to look realistic. This tutorial offers two examples.

For this tutorial, the source images come from a 2008 contest, called Asian Girl, on photoshoptalent.com (a great place to learn more about using Photoshop!), and from stock exchange (great place to get high quality free images through Creative Commons license). The tutorial was done in Adobe CS2, but the tools are the same in all versions of the Creative Suite - only the layout may look different.

1. Make a copy. Open your Layers palette if it's not already open (Window -> Layers, or F7). Make a copy of your original image by dragging the background layer to the Create A New Layer icon, then letting go. (Most of these steps are guidelines; this one is a rule: ALWAYS work on a COPY of your original image.)

This is the base image of the bucket of apples, masked and placed on an orange background for visibility in this tutorial. Notice that the bucket already has a strong natural shadow around the rim and along the handle.

 

This is the hand that was added to the scene. The hand's natural shadows match the bucket pretty well; they share a very similar light source (light is coming from above left).

 

This image shows the "regular" Drop Shadow layer effect added:

Notice the problem areas that emerge with the "default" Drop Shadow:

So, now that we know what's wrong, we're going to fix it.

 

2. Make a copy of the hand layer.

 

"Turn off" or discard the Drop Shadow layer effect from this new, top layer. (Click on the eye icon to toggle Effects on and off.) "Turn off" the top hand (copy) layer altogether by clicking on the eye icon; this keeps the layer safe and out of your way.

 

3. Control and shape the shadow with Eraser Tool. Click on the shadowed hand layer to activate it. Using the Eraser Tool at 100% strength and opacity, begin trimming away the parts of the hand that cast unwanted shadows.

 

4. Done! Turn the top (no shadow) layer back on and check your work. This is the finished result:

 

Here is another example of this simple technique applied to a different Effect.

To make the peppermints look as if they'd been pushed into the icing "snow" of this Gingerbread House, Pillow Emboss effect was used. However, because the mints extend beyond the roofline, so did the effect.

1. Individual peppermint layers were copied; Pillow Emboss effect was "turned off" top layers of mints.
2. For this project, the shape of the snow on the roof line makes a great guide for erasing. Holding CTRL, select the roof snow layer. Now invert the selection (Select -> Inverse), meaning everything except the roof snow is now active.

 

3. Using the Erase Tool at 100%, trim the bottom mint layers - with Pillow Emboss effect applied - to the snow and roofline guide:

 

Done! Here's a look at one completely trimmed mint:

 

This is an "after" close up with all layers active, followed by a look at the completed Gingerbread House. Result: Pillow Emboss effect only appears on the white icing "snow."