NEW YORK - When you put your carry-on luggage containing undeveloped film through the airline security inspection X-ray machine, are you playing Russian roulette with your once-in-a-lifetime vacation picutres?

Everyone knows that strong X-rays can damage unprocessed film, but are the airport screeners strong enough? And how many times must the film be put through before damage is noticeable?

A lawsuit against the Federal Aviation Administration (FAA) tentatively set to go to trial in the fall may finally settle that question. Until then, the peripatetic photo buff still hasn't gotten a clear picture of just how much damage - if any - the airline X-ray machines are doing.

The 4,000-member Chicago-area Camera Clubs Association and Sima Products Corp. filed the suit against the FAA in Chicago Federal District Court in January 1977. They want the FAA to change signs at all U.S. airports so travelers are warned that the X-ray machines used to screen carry-on luggage are "not film-safe." The signs currently on display say inspection will not effect ordinary undeveloped film.

The camera clubs and Sima - which makes "Filmshield," a lead-laminate reusable pouch that protects film from X-rays - claim they have conclusive proof, after extensive testing in several U.S. airports, that the X-ray machines are capable of damaging unprocessed film.

However, the National Association of Photographic Manufacturers (NAPM) and the world's largest maker of film say the equipment used to screed hand luggage by all scheduled domestic carriers in the United States is safe for normal film.

NAPM, the trade association of the domestic photographic equipment and film manufacturing industry, said it reached its conclusion after extensive laboratory and field testing.

"Domestic air travelers need not be concerned about the welfare of their film, even if they go coast to coast several times," said Joseph T. Morris, executive vice president of NAPM. "The odds of anything going wrong to damage the film are infinitesimal." A spokesman for Eastman Kodah reiterated the NAPM conclusion.

But both men agreed that "all bets are off" when it comes to flying a foreign airline - especially overseas.

Morris said there have been several instances in which X-ray exposures at foreign airports have "really zapped" the unprocessed films.

Said the Kodak man: "Of the millions upon millions of rolls of film sold, last year he received only 78 complaints of film fogged by airline X-ray exposure. And those he could identify he traced to overseas airports." He said the main trouble spots are in the Middle East and in Southeast Asia.

Irwin Diamond, president of Sima, said: "Thorough scientific field testing leaves absolutely no doubt that airport X-rays can damage undeveloped film of all types." He cites a comprehensive field test commissioned by Technical Photograph magazine and conducted over a year's time by technical consultant John Rupkalvis.

Rupkalvis ran tests at airports in Minneapolis-St. Paul, Chicago and New York. The vast majority of the film was protected by "Filmshield," while others were run through the X-ray screener unprotected. The protected film showed no fogging, he said. About half the unprotected film showed a trace of fog, but probably not enough to "concern any but the most discriminating user." Seventeen percent of the unprotected film showed fog that was "definitely noticeable, but not necessarily objectionable." And there were "a few examples" in which the fog was so severe as "to render the film completely unusable."

His conclusion: "If anything stood out from my testing, it was just how unpredictable the possibility of fog is."

Diamond notes another field study conducted by high school senior David Joseph at Chicago's O'Hare International Airport. The teen-ager said in his report: "The fluoroscopic inspection devices definitely harm photographic film by increasing the grain size and the exposure index and by lowering the sharpness as well as worsening the contrast." His study won first prize at the Illinois Science Fair.

So what is a sky-bound vacationing shutterbug to do? Well, everyone agrees that if you have the slightest trepidation about sending your film through the X-ray machine, ask for a hand inspection of your carry-on luggage. Then, after the security guards have inspected your carry-ons, make sure that are not automatically put on the X-ray conveyor anyway. It's been known to happen.

By the way, if you're really uptight about the X-rays and fear of fogging, packing your film in luggage destined for the airline's baggage compartment isn't the answer. The airlines are very secretive about their screening of stored luggage, but they've been known to scrutinize it by X-ray.

NAPM's Morris has other tips on X-ray dangers for vacationing camera buffs. Be very careful at industrial and medical complexes where radiation may be around. The same is true when visting such public places as the Senate Office Buildings in Washington, where heavy-dose X-ray machines are used to screen personal effects. Again, ask for a hand inspection. And if you're mailing your film back to the United States from a foreign country, use a commercial mailer or mark the package "Undeveloped film: Don't X-ray."

Morris said that if you put the film in a larger package or don't mark it, there's a good chance it will be X-rayed by U.S. postal inspectors, and they also use a heavy-dose machine.