After your home, your photographic equipment is your single most expensive investment. Okay, after your car, too. And your stereo. And your television set. And Well, regardless of what you have invested in your camera and accessories, the fact is that you need to keep your gear in tip-top shape if you're going to be able to rely on it when you need it. After all, what good is a camera if you find out that it malfunctioned on your recent trip to Greece-- after you filled up two 512mb memory cards or shot 12 rolls of film!

Fortunately, photographic gear is pretty durable. With just a minimum of effort, yours should last a lifetime or longer. Here are a couple tips to ensure its longevity.

Camera. Whether it's a full-featured single-lens reflex (SLR) or a compact camera, you should keep your camera in a case or camera bag until use. Be sure the bag has plenty of foam padding to reduce the chance of camera damage from bumps and to protect it from dust and dirt. Specially made foam inserts are available at many photo stores and may be custom cut to fit a wide variety of bags. And take special care when using a camera at the beach. Even a grain or two of sand can trigger a trip to the repair shop. One grain stuck between the gears in a dab of lubricant quickly breaks into several grains, which break into several more-all the while working their way through the camera's system and gradually wearing away delicate parts. So avoid shooting with sandy hands, and always keep your camera in a sealed bag when not in use.

Lenses. If your camera accepts interchangeable lenses, keep them in your camera bag, too. Place caps on both front and rear lenses to protect delicate elements from dust, dirt, and scratches (replacement caps are available for a nominal price from your local photo dealer). If a lens surface should happen to get dirty, use a specially made photo lens cloth to clean it. Just remember to be gentle, and never use eyeglass tissues or cleaners. They may contain solvents damaging to lens coatings.

Film. Everybody knows how delicate computer disks are. We keep them out of sunlight, free from dust, and clear of magnetic fields. But photographic film? We store it in a bag on the top closet shelf. We carry it in our purses and pockets, run it through airport X-ray machines, and shoot it long after its expiration date. In fact, we treat it like dirt and expect it to reward us with perfect exposures every time.

Well, the joke's on us, because photographic film is affected by heat, light, humidity, X-rays, dust, dirt, and sand-every bit as much as computer disks. So how can we protect it from the ravages of a hostile world? For starters, buy only fresh film. Out-of-date film may still "work," but its colors have likely shifted and overall results will be poor. Store all unused film in the refrigerator and warm for 15 minutes before using. For longer storage periods, keep it in the freezer and warm for 30 minutes before use.

When transporting film, keep it away from direct sunlight and high heat. And never allow it to be X-rayed, which can be cumulatively damaging, especially with today's faster film. Instead, place all unexposed film in a clear plastic bag and request a hand check. It takes a little work to keep photo gear safe and secure. But the results will be equipment you can rely on for years to come.