Why does each segment of holographic film have complete information?

Whether holographic photography or the earliest silver disk photography, their mystery lies in the recording of light. All light has three properties, namely its intensity, color and direction. Early silver photography and black-and-white photographs can only record the changes of light and shade, while color photographs can also reflect their colors by recording the wavelength changes of light. Holography is the only photography that can capture three properties of light at the same time. Through laser technology, it can record the direction of light incident on the object, and then refract it to reproduce the real scene of the object in three-dimensional space realistically.

Holography refers to a new photography technology, which records all the information of the amplitude and phase of the reflected wave of the object being photographed. Ordinary photography records the light intensity distribution on the surface of the object, but it can't record the phase information of the reflected light of the object, so it loses its three-dimensional sense. Holography uses laser as the illumination source, and divides the light emitted by the light source into two beams, one of which is directly directed at the photosensitive plate, and the other is reflected by the subject and then directed at the photosensitive plate. The superposition of two beams of light on the photosensitive plate produces interference, and the sensitivity of each point on the photosensitive plate changes not only with the intensity, but also with the phase correlation of the two beams of light. Therefore, holography not only records the reflection intensity on the object, but also records the phase information. When the human eye directly looks at this photosensitive film, it can only see interference fringes like fingerprints, but if it is irradiated by laser, the human eye can see the three-dimensional image of the original object through the film. Even if only a small part of the holographic image remains, it can still reproduce the whole scene.

Holographic principle is that "a system can be completely described by some degrees of freedom on its boundary", which is a new basic principle based on the quantum properties of black holes.