We investigate a f ( R ) modification of gravity that is exponential in the Ricci scalar R to explain cosmic acceleration . The steepness of this dependence provides extra freedom to satisfy solar system and other curvature regime constraints . With a parameter to alleviate the usual fine tuning of having the modification strengthen near the present , the total number of parameters is only one more than \Lambda CDM . The resulting class of solutions asymptotes to w = -1 but has no cosmological constant . We calculate the dynamics in detail , examine the effect on the matter power spectrum , and provide a simple fitting form relating the two .