The original audio-only portable MP3 players have evolved into multimedia devices with a color display for navigating onscreen menus, viewing album art, looking at slide shows of digital photos, and most recently, watching movies and TV shows. They're also adept with text and graphics and can put up PowerPoint presentations. Most of them will even have TV-out capability to transfer images to the big screen. The category itself has grown to include larger and more sophisticated offerings such as personal video players (PVPs) and mobile digital video recorders, (MDVRs).

But how good are these tiny screens? Are they toys, pretentious devices, or high-quality displays with excellent image and picture quality? To answer this question, I employed the same high-powered methods we use for testing and evaluating high-end HDTVs at DisplayMate Technologies.

While the screens seem small, ranging from 1.8 to 4 inches diagonally, angular size is what matters to the eye. To the retina, they appear much closer in size to a living room TV because they are viewed up close. In fact, a 36-inch TV at a typical viewing distance of 9 feet has a visual angle that is only double that of a 2.5-inch iPod at its typical viewing distance of 16 inches. Since an iPod also has roughly half the pixel resolution of a standard-definition TV, the images appear to have comparable sharpness to the eye. More impressive is the 4-inch Creative Zen Vision, which has three-quarters of the visual angle of a 36-inch TV but roughly the same resolution; to the eye, it appears to be 25 percent smaller but 33 percent sharper than the TV.

While we will check on all aspects of the players' display performance, it is their color and grayscale accuracy that determines how suitable they are for digital photos, movies, and TV shows. The differences between the players are striking. We'll see performance that is sometimes impressive and other times disappointing.

Outline and sidebars
This article is accompanied by several sidebars with additional information on player picture quality. This main section will concentrate on providing the results and explaining what they mean and why they are important. It will also clear up some common misconceptions. We will examine contrast under both bright and subdued ambient lighting, as well as how it varies with the viewing angle. We will also examine their brightness, their color and grayscale accuracy, and their TV-out picture quality.

The first sidebar will let you check the picture quality of your player (and your computer monitor and HDTV) with a test photo, then compare it to a specially optimized photo for each of the tested players. There is a sidebar on improving player picture quality that explains what steps you can take to improve the picture for both the internal screen and the TV-out. The sidebar on technical information provides technical details and results of the lab tests.

Acknowledgements
Special thanks to the Konica Minolta Instrument Systems Division for providing a longterm loan of the CS-200 Spectroradiometer. Special thanks to Lauren Soneira for getting me interested in her Apple iPod, which was the seed that produced this article.

Dr. Raymond Soneira is president of DisplayMate Technologies, which produces video calibration, evaluation, and diagnostic products for consumers, technicians, and manufacturers. He is a research scientist with a career that spans physics, computer science, and television system design. Dr. Soneira has authored more than 35 research articles in scientific journals in physics and computer science, including Scientific American.