Compositing Quick Tips - The Photoshop: Professional Retouching and Compositing Tips, Tricks, and Techniques - page 310

Tip
This technique can also be used on a scene or view. It's a good thing to do if
you're going to add additional color effects, because the colors will be much
more balanced and even.
Matching Color #2
I learned this incredibly simple but effective technique from my friend Pete Collins of
KelbyOne. It's another technique for subtly matching color in composites, but it's also
great for adding a slight haze to distant objects, which is something we see in the real
world.
Figure 5.35 is a composite picture of a rhino that I created; we'll also be working on it in
the projects section of this topic.
Figure 5.35
In Figure 5.36 you can see the layer stack, including the cutout of the rhino. All you need to
do for this technique is lower the opacity of the layer to no less than 90%. This introduces
a little color from the background and adds a slightly hazy effect. You're done! Techniques
don't get much simpler or quicker than this.