LEGISLATORS approved a fivefold increase in the maximum fine for cinema operators who allow people under 18 to see Category III films. The current penalty is $10,000. The Secretary for Recreation and Culture, James So Yiu-cho, said prosecution would only be considered after two warning letters had been issued. Cinema operators have, however, complained that it is difficult to prevent youngsters from seeing such films. Instead, the Hongkong Theatres Association wanted fines imposed on youngsters caught at Category III films. Independent legislator Timothy Ha Wing-ho, who chaired the bills committee studying the Film Censorship Ordinance, said the increased fine sent the right message to the public and the film industry. ''The number of Category III films being shown in Hongkong is increasing,'' he said. Most legislators agreed that under-aged viewers should not bear the criminal responsibilities of breaking the law. ''Members shared the views of the administration that the taking of any deterrent measures on the under-aged should be handled with extreme care,'' he said. Liberal Party legislator Selina Chow Liang Shuk-yee said, however, that it was unfair to lay responsibility only on cinema operators. She said it was difficult to detect under-aged viewers and the recreation and culture panel should review the issue further. Liberal legislator Emily Lau Wai-hing called for the deletion of clauses relating to political censorship in the ordinance. She said the clauses violated the Bill of Rights and the International Covenant on Civil and Political Rights.