Compositing Quick Tips - The Photoshop: Professional Retouching and Compositing Tips, Tricks, and Techniques - page 301

Figure 5.26
Note
You don't have to be completely accurate with the shape you paint, as long as it
resembles a shadow.
Matching Color #1
Another make-or-break situation for composite images is when the color of the background
scene and the color of the assets being added don't match.
For example, Figure 5.27 shows the original studio shot of the model and Figure 5.28 is
where a new background has been added, using the Blend Mode compositing technique we
covered in Chapter 2 . The warm color of the model doesn't match the cool and desaturated
color of the background, which means the composite doesn't work.