We describe the novel application of light coupling masks (LCM) in the lithographic patterning of fine structures in diamond films. A PDMS mask was used in the exposure of complex patterns of gratings in AZP 1205 resist on a substrate of Al/ diamond. The profiles of these grating patterns were then modified on a localized scale by a process of reflow of the resist. We report on the transfer of the patterns formed in resist by the LCMs into the diamond film using a sputtered Al layer as a mask. The two-stage process comprised etching of the pattern into the Al followed by transfer into the diamond film using CF4/ O2 and CHF3/ O2 gases. The presence of O2 in the CF4/ O2 and CHF3/ O2 gas mixtures produced Al oxides on the surface of the mask. The etch selectivity of the mask was greater in CF4/ O2 than in CHF3/ O2 gases and was only weakly dependent on the concentration of O2 (0-12 sccm).