Eloquent photos capture Nicaraguan upheaval; Nicaragua: June 1978-July 1979, by Susan Meiselas. New York: Pantheon Books. $ 22.95 in hardcover. $11.95 in paperback.

If, as his peers have suggested, World War II was Robert Capa's photographic coming of age, then Nicaragua served the same function for Susan Meiselas. She easily won her photographic spurs in the horrendous combat in Nicaragua in the late 1970s, which grew out of the successful Sandinista guerrilla effort to topple the Somoza family dictatorship.

That conflict mushroomed into a veritable civil war. Thousands, perhaps as many as 50,000, were killed, as the fighting flowed over the whole Central American country. Miss Meiselas was there throughout, spectacularly recording the violent struggle. Her photographs are graphic and poignant. They evince a sympathy with humanity and a sense of the ugliness of war. Inevitably, she favors the Sandinistas; they become her heroes, while dictator Anastasio Somoza Debayle and his legions are clearly the villains. Yet there is an objectivity in her message, an objectivity born of the brutality of war in which suffering has no favorites.

Through it all, however, war's ugliness is mixed with Nicaragua's haunting beauty. This dichotomy is ever so evident in her countryside photographs; it comes up in the faces of her Nicaraguans, the majority of whom are young, for, after all, one-half of all Nicaraguans are under the age 20. Yet that same image is also there in the elderly captured by Miss Meiselas's camera.

One should not look at Miss Meiselas' photographs for an explanation of the Nicaraguan conflict. It is enough that they tell the story of the conflict. It is good also that they are so handsomely put together in this book. The absence of captions accompanying the pictures leaves the viewer asking questions that the pictures do not readily answer. Pantheon chooses instead to group the captions together at the end of the book. This reviewer suspects that the publisher reasoned the captions might take away from the message in the photographs. Perhaps. But without captions, that message seems less clear, and the system of going to the end of the book seems to clumsy.

Carping, asice, it is good to have Susan Meiselas's able work so readily available. Let's hope her equally meaningful photographs of today's ongoing struggle in neighboring El Salvador will eventually be collected in an equally handsome companion volume.