Digital imaging has spawned more how-to books than film photography ever did, making it harder than ever to separate the instructional wheat from the chaff. We've found that the best of these books are often a joint effort, with two photographers filling in the gaps in each other's experience and knowledge. Perfect Digital Photography: Expert Advice for Capturing, Correcting, and Printing Exceptional Images (McGraw-Hill, $40) is just such a book. Co-authored by Pulitzer Prize-winning National Geographic photographer Jay Dickman, a member of both the Olympus Visionary and Lexar Elite groups and director of the popular First Light Workshops program (www.firstlightworkshops.com), and photographer Jay Kinghorn, an Adobe Photoshop Certified Expert and noted fine-art printmaker, it is a full-service tutorial that never puts technical over aesthetic considerations. The following excerpt is one of the book's 17 self-contained "How To" lessons, which alone are worth the price of admission.