Experiments on the sodium D lines and an 0.82‐Å separated doublet in the iron spectrum have shown that holographically recorded dichromated gelatin diffraction gratings have resolving powers within 90% of theory. The diffraction gratings are of excellent optical quality, have background scatter less than 10−4 of the signal, are ghost free and have greater than 90% first‐order diffraction efficiency. Blazing is accomplished by rotating the grating to the incident angle which satisfies the Bragg condition for the blaze wavelength. The 3‐μ‐thick transmission gratings can be employed from 0.25 μ to at least 15 μ, with gelatin absorption interfering only at 2.6–4.0 μ and 5.8–8.5 μ.