YOKOHAMA, Japan >> For some Pacific Rim leaders, this will surely come as a relief: No kimonos or other special attire for the annual group photo.

Over the years, one of the most memorable moments of the annual Asia-Pacific Economic Cooperation summit has been what’s come to be called the “silly shirts” photo, often representing the host country’s culture.

The 21 APEC leaders have posed for together in Javan batik shirts (Indonesia in 1994), flowing ponchos (Chile in 2004) to Vietnamese “ao dai” — elegant silken tunics in which several of the leaders were visibly ill at ease — in 2006.

But this year in Japan, the leaders were instructed to come in “smart casual” for Saturday’s photo, said a government official, who spoke on condition of anonymity, citing department rules.

The Japanese official cited the timing for the photo session, which falls between a traditional Kabuki theater performance and an official dinner hosted by Prime Minister Naoto Kan, as one possible reason for the relatively staid choice.

The typical tight-fitting traditional kimono is not very comfortable or suitable for a photo session, said another official, though he did not say why.

In this relatively frugal post-global financial crisis era, perhaps it makes sense.

The tradition started in 1993, when then-President Bill Clinton handed out bomber jackets at the summit at Blake Island, Washington.

Over the years, the choices have become more interesting — and much more colorful.

In Japan, formal attire involves either a business suit, a morning suit or a kimono — with or without matching wide-legged hakama trousers. Taking pity on their guests, the organizers opted, as they did in Osaka in 1995, for the simplest choice — a jacket, shirt and slacks, without a necktie.

Next year’s summit will be held in Hawaii, and President Barack Obama joked last year that he looks forward to seeing all the leaders “decked out in flowered shirts and grass skirts.”