Blending the Layers

To blend the layers, I first created a Layer Mask for the Shadow Elephant Layer and then began to slowly mask off the shadow areas, allowing the Highlight Elephant Layer to show through where appropriate. I used a blurred brush set at different opacities to reveal the highlights in subtle, blended manner.

This is where masking is invaluable, allowing you the freedom to experiment, start over, tweak, mask and unmask to your heart's content.

The key is to study the lighting of other objects in the scene, and then match this to the elephant. When done right, it can be surprising how effective this technique is in recreating the fall of light and shadow.

Adding the Street Shadow

Next I needed to add the huge shadow cast by the elephant -- a touch which adds a good dose of realism to the scene. There are many ways to add shadows -- using the Drop Shadow feature is one, but it won't work in this case. This one I had to do freehand.

Again, I looked at the shadows cast by the other objects in the scene -- their direction, color, and blur -- and let them be my guide. The cars shadows are at least twice as long as the height of the cars, so I knew the elephant's shadow was going to extend out of the picture. That's good, as it simplified my work.

On a new layer set to Multiply Blend mode, I painted in the basic shadow of the elephant in deep blue, but the shadow of the trunk and the tusk were more difficult. By experimentation I eventually arrived at a painted outline that looked right.

I was careful not to paint the shadow over the two cars in the shadow, as it darkened them far too much. Instead I individually darkened these cars with the Burn Tool.

Lastly I tweaked the color and brightness of the shadow layer until it matched with the cars shadows. Then added a Gaussian blur to match the shadow blur of the cars.

Finishing Up

And finally I added tiny people standing around and riding their bicycles, gawking up at this humongous creature walking the wrong way down a one way street.

Mind you this is a pretty extreme example of how to match lighting between dissimilar images. But this trick can come in handy for far simpler objects when the lighting just doesn't match.