The method for controlling the reconstruction wavelength is presented for Lippmann holograms recorded in dichromated gelatin. Two different kinds of gelatin are mixed to prepare the dichromated gelatin. One is of high bloom strength and the other is water soluble which is washed out during processing. The reconstruction wavelength can be shifted to short wavelengths and controlled freely to a certain extent by varying the ratio of the two kinds of gelatin. Experimental results are presented and the asymmetry observed in the selectivity curves is discussed.