Find a picture in need of retouching, or download one from this book's page on the Sams Web site. Clean it up as much as you think necessary and save a copy. Convert the copy to a duotone. Hand-tint the original using transparent tints. Notice how the duotone looks like rotogravure pages from the 1930s, whereas the hand-colored version looks like photos from the '40s or '50s. Think about how you might use these techniques with your own work.