A picture is supposed to be worth a 1000 words. Over the years,Amnesty International’s posters have spoken and stirred thoughts and debates across the world. This year,Amnesty,and its iconic candle in barbed wire logo,(made by British artist Diana Redhouse),turns 50. As observances ring out for its wide-reaching work for human rights,so does praise for its incredible poster art,which had featured works by such greats as Pablo Picasso,Joan Miro and Annie Leibovitz. After opening in Britain in March,an exhibition of the half-a-century worth of landmark poster collection will travel across the world. The first Asian stop will be Thailand.