n = 0.01;
t = Table[Sin[i^2 - j^2], {i, -4, 4, n}, {j, -4, 4, n}];
r1 = ReliefPlot[t,
   ColorFunction -> ({Specularity[White, 1], Hue[0.5, 1, 1]} &),
   BoxRatios -> {1, 1, 0.7}, LightingAngle -> {Pi/6, Pi/3}];
r2 = ReliefPlot[t,
   ColorFunction -> ({Specularity[White, 100], Hue[0.5, 1, 1]} &),
   BoxRatios -> {1, 1, 0.7}, LightingAngle -> {Pi/6, Pi/3}];
r3 = ImageData@r1 - ImageData@r2;
{r1, r2, Image[r3]}