Lippmann's process foreshadowed laser holography, which is also based on recording standing waves in a photographic medium. Denisyuk reflection holograms, often referred to as Lippmann-Bragg holograms, have similar laminar structures that preferentially reflect certain wavelengths. In the case of actual multiple-wavelength colour holograms of this type, the colour information is recorded and reproduced just as in the Lippmann process, except that the highly coherent laser light passing through the recording medium and reflected back from the subject generates the required distinct standing waves throughout a relatively large volume of space, eliminating the need for reflection to occur immediately adjacent to the recording medium. Unlike Lippmann colour photography, however, the lasers, the subject and the recording medium must all be kept stable to within one quarter of a wavelength during the exposure in order for the standing waves to be recorded adequately or at all.