Zagreb, Yugoslavia — When the producers of ''Sophie's Choice,'' the recently released motion picture, could not film in Poland because of martial law, where did they go to find the streets of Warsaw?
When producers of ''Mehmed My Hawk,'' a film about Turkish bandits starring Peter Ustinov, could not film in Turkey because of the film's political content, where did they go to find the Anatolian Plateaus?
At first it seems an odd choice. But increasingly, Western filmmakers are turning to Yugoslavia to find locations for their films, no matter how diverse the themes.
Yugoslavia has as its main selling point a breathtaking variety of natural scenery, from forests, snow-capped mountains, and rolling plains, to a Mediterranean-style seacoast. The various conquerors who ruled over Yugoslavia during the centuries, including Turks, Italians, and Austrians, have left behind an amazing array of architecture. Mosques, forts, castles, monasteries, and cathedrals can be found in a relatively small area.
Another advantage of Yugoslavia, the country's film executives contend, is the freer political atmosphere in their country compared to the Soviet bloc countries. It is better for the morale of cast and crew, they argue, and can make a difference if the film is about a Russian subject. Although Hungary, Romania, and Czechoslovakia also offer services for filming, Yugoslavia has captured a large part of the market.
''We have everything you need, from China to Western Europe,'' enthused Milomar Marinovic-Mikan, public relations director of Jugoslavia Film Company in Belgrade. ''The Adriatic coast is typically Mediterranean. Northern Yugoslavia is like the Russian steppes. We have big mountains like Austria or the Himalayas.''
Most of the Western filmmakers who shoot on Yugoslav soil negotiate coproduction agreements with the Yugoslav film companies. In 1980 there were 17 coproductions with Yugoslav companies, including television. In 1981 there were 20, and the number is still increasing.
Yugoslav companies have begun to market their services more aggressively to Western moviemakers. Jadran Film Company of Zagreb, which handles many of the foreign productions that come to Yugoslavia, has opened up an office in Century City, in Los Angeles.
They even offer package deals. Jadran Film will provide services including hotels, meals, transportation, and set construction, all for an affordable price.
''A small Russian village costs a fortune to reconstruct in the States,'' argued Zdravko (''Mike'') Mihalic in a recent sales-pitch-style interview in Zagreb. Yugoslavia, he said, had Russian-style villages in abundance, and a Slavic population to go with it.
Jadran Film's glossy brochures feature village scenes from ''Fiddler on the Roof'' that were filmed in Yugoslavia. Jadran Film was a production partner in the film.
''Prices are 60 percent lower'' than in the United States, continued Mr. Mihalic. ''Building sets are cheaper, extras are cheaper, horses are cheaper. We have a lot of horses.'' Stuntmen, studios, and cameramen are also available at cheaper prices.
Mr. Mihalic also gives his sales pitch for Yugoslavia's varied scenery. ''In 'High Road to China,' in 100 kilometers we shot Egypt, Afghanistan, China, and Tibet.''
An American Yugoslav coproduction called ''After the King,'' starring Candice Bergen and Malcolm McDowell and about King Arthur's court, is now being filmed in the fairy-tale walled city of Dubrovnik. The fantastic caves of Postojna in Slovenia will serve as a backdrop for Merlin the magician.
The award-winning film ''The Tin Drum,'' directed by Volker Schlondorff, was also a Yugoslav coproduction.
Still, the movie business is a two-way street. Yugoslavia imports 180-220 foreign films a year, 70 percent of them from Hollywood.