Vray rendering lost skin detail


I put a detailed skin texture in subsurface slot and set overall color to white,I think it’s the right way,but the rendered image lost most detail such as pore and flaws in the texture(the first image),if I put the skin texture also in overall texture,the rendered image bacame much clear and preserved all the detail(the second image),so is it necessary to put texture in overall slot,if not,how to preserve details?