I am pretty sure I read this short story in an American magazine in the late 1960s or early 1970s. The time is the future, when an extremely realistic 3-D movie system has come into use. It has revolutionized entertainment, but there is a catch: the 3-D cameras project a form of radiation that is cumulative and eventually fatal - to be a 3-D star is a death sentence.
The story is told from the POV of a member of the 3-D industry, who describes how two young people (a man and a woman) are so desperate for fame they voluntarily become 3-D stars and eventually pay the price. The story ends with their last film being previewed in front of a live audience. One of the stars has died and the other has terminal radiation burns (can't remember which one). The dying star crawls out onto the 3-D stage, confusing the audience; they weren't expecting a horror story. When they finally realize what is happening there is pandemonium.