Software Secrets: Preserving Shadows in Photoshop

Whether you are teaching yourself or currently learning in a classroom, chances are, one of the first things you’ll learn how to do in Photoshop is a simple composite. Carefully cutting an item out of one photo and placing it into another. If you’re anything like me, this alone is enough to keep you preoccupied for months.

After the initial rush of discovery wears off, also like me, you may find yourself thinking, “actually… this looks pretty bad.” There are a number of reasons this might be the case… but the main culprits are typically a mismatch of lighting or perspective between the final image and the donor. Today we’ll look at how to preserve shadows while creating a composite.

Due to its simplicity and the polished look of the final result, this technique is commonly used in advertising. If you’ve seen any ads recently that depicted a person or product against a colorful background, chances are it was creating using this technique. With just a simple white backdrop, we’re granted the full spectrum of the rainbow.

We’ll begin with this image here. It’s got a white background and some interesting movement we can play with.

The first thing we’ll do is duplicate our image. We’ll rename the top layer coffee and the bottom layer shadow. Next, we’ll add a layer mask to the coffee layer, where we’ll carefully mask out our shape. By using a mask, we’re working non-destructively, so don’t worry about getting it right on the first try, we can always come back and make adjustments. To check our mask, let’s add a layer at the very bottom of our stack and give it a solid pink fill. We’ll rename this layer background. If we turn off the shadow layer, we can see that our masked out coffee now looks like this.

We’ve got a few artifacts around the edge of the mug, but this will work fine. Now we want to reclaim those shadows from the original image. We’ll accomplish this by first clicking the layer mask of the coffee layer, and then holding alt-shift or apple-shift while we drag and drop it onto the shadow layer below. This creates an inverted copy of our mask. If we turn off the coffee layer, our image now looks like this.

Not very useful, but if we change the shadow layer’s blend mode from normal to multiply…

Much better. Next, we’ll add a levels adjustment layer right above the shadow layer. Right-click it and create a clipping mask. This way when we adjust the values it will only affect the shadow layer. Using our new levels adjustment, we’ll bring down the highlights until the muddiness of the background starts to disappear.

Now we’ve got a pretty great-looking composite, but there’s one last step we can take to make it even better. Let’s add a solid fill layer and make it a clipping mask to our shadow layer. We’ll set its blending mode to color and choose a darker version of our pink background for its fill. The effect is pretty subtle so let’s take a closer look to see what we’ve done.

In the image on the right, we can see that by shifting the hue of the shadow to match the pink background, we were able to better mimic how the lighting in this sort of environment would function. So there you have it, a perfectly masked cup of coffee ready compositing.