Why do holograms record both the amplitude and phase of light waves?

Holograms record both the amplitude and phase of light waves to achieve three-dimensional realism, a feat that standard photography cannot accomplish because it only captures amplitude.12

In standard photography, the intensity of light is recorded, but the phase information—which contains the precise details regarding the depths, heights, and contours of an object—is lost. By introducing a coherent reference beam that interferes with the light reflected from the object, holography creates an interference pattern on the recording medium.23

This interference pattern encodes the phase information as variations in the intensity of the recorded fringes. When the hologram is later illuminated, this stored information allows the original optical field to be reconstructed, effectively recreating the light waves as they existed when they reflected off the object. This reconstruction provides the three-dimensional characteristics and parallax that allow the viewer to perceive depth and see the object from different perspectives.32