We study a particular random field Ising model in dimension 2 at 0 temperature. On each site the random field is either + ∞ with probability p/2, - ∞ with probability p/2 or 0 with probability 1 — p. Using finite size scaling arguments, we show that for small p, the average correlation function between two spins at distance R decreases like R-η( p) where the exponent η(p) = 2 πp + O(p2). The assumptions made to obtain this result and the possible generalizations to other random field models are discussed