Secret car testing has a long and storied history. This Alfa Romeo was snapped during testing in Italy in 1952. The car wouldn't make its debut until the Le Mans Grand Prix in France a few days later.

STF/AP

Auto Spies on the Prowl

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In Hollywood, celebrities find themselves perpetually hounded by paparazzi, those intrusive photographers and videographers who jostle one another and their subjects for the perfect shot. These images sell for hundreds or even thousands of dollars to magazines and tabloids, and Web sites worldwide.

The situation is similar in the world of automotive photography, except that these spy photographers are hunting for new and previously unseen cars instead of overexposed starlets. With so many car magazine titles out there, editors place great value on presenting information to their readers before competitors have a chance to do so.

Spy photographers are usually independent contractors. They stalk their prey by driving to locations where they expect engineers to be testing prototype vehicles. Then, they set up their equipment -- expensive cameras with massive telephoto lenses.

Car magazines pay decent rewards to photographers that bring back compelling photos of new and secret automobiles. Compensation can range from $500 to $900 for a good spy shot [source: Woodyard].

While photographers often obtain their pictures covertly, they can get up close and personal with the vehicles to try to capture more detail. Sometimes, the situation can turn tense, as the engineers who do the testing are tasked with keeping the cars as secret as possible. Sometimes they will crowd around a test car to shield it with their bodies. Sometimes they will cover the cars with a shroud.

Frequently, manufacturers will attempt to camouflage the design of their test vehicles by applying black vinyl to their surfaces. To further confound photographers and competitors, carmakers might add foam body inserts to conceal the car's true shape. Another trick is to cover the car in complex patterns that confuse the eye (and the camera). Manufacturers will even go so far as to cover up any markers, medallions or other logos, both inside and outside the car, that might indicate who made it.

Go to the next page to find out exactly how the test procedures themselves work, who carries them out, what they measure and what they accomplish.