Commercial Projectors

The persistence of vision should be compared with the related phenomenon of Beta Movement and the Phi Phenomenon. A critical part of the understanding of the aspect of visual perception is that the eye is not a camera; that is, there are no "images per second" in the eye. Instead, the eye/brain system has a combination of motion detectors, detail detectors, and pattern detectors, the results of which combine to create the visual experience.

The frequency at which the change of images becomes invisible depends on the level of illumination. Generally, 16 images per second (or, of English, frames per second: fps) is considered the lowest frequency at which humans perceive continuous movement. (It is interesting to note that this threshold varies between different species, a higher proportion of rods in the retina result in a higher threshold frequency).

It is possible to appreciate the space between images by closing and opening the eyes quickly. If it's done fast enough, at some point the transition will be caught. This will not work with television due to the persistence of phosphorus or with LCD or DLP projectors due to the continuity of the image, although some digital projection technologies can show artifacts.

Since the birth of sound cinema, almost all commercial cinema projectors project at a frequency of 24 images per second. This speed was chosen for financial and technical reasons: it was the lowest frequency (so it required less film) to which satisfactory reproduction and amplification of sound could be made. There are, however, some special formats such as Showscan or Maxivision that project at higher frequencies, often 48 images per second.

Silent films were not usually projected at constant speeds, but varied during projection at the discretion of the projectionist, often by notes provided by the distributor. In Spain, one of the leading manufacturers of film projectors was the company Ossa de Barcelona, ​​also known as a motorcycle brand.

Film Projector

A cinematographic projector is an opto-mechanical device used to show films by projecting them on a screen. Most optical and mechanical components, except those concerning lighting and sound, are also present in cinematographic cameras.

The machine projects, at regular intervals of a few hundredths of a second, a beam of light on the frames of a film; that beam of light is increased and inverted by a lens that focuses the resulting image on a screen.

The cinematography was patented in February 1894 by the Lumière brothers, and the first public exhibitions were held in 1895. There are currently "digital cinematographic projectors" that project an image generated by digital media, without making use of a film, but of the beam of light and the lenses.

The first film projector was the zoopraxiscope, invented by the British photographer Eadweard Muybridge in 1879. The zoopraxiscope projects images from glass discs that rotate in rapid succession to give the impression of movement. The detained images were painted on the glass initially, like silhouettes. The second series of discs, made in 1892-1895, used a set of drawings printed on photographic discs, then colored by hand.

A more sophisticated film projector was invented by Frenchman Louis Le Prince while working in Leeds. In 1888 Le Prince released a patent for a 16-lens device that combines a moving image camera with a projector. In 1888, he used an updated version of his camera to shoot the first film in history, the Roundhay Garden Scene ([garden scene of Roundhay]). The images were exhibited privately in Hunslet.

The Lumière brothers invented the first successful film projector. They made their first film, La Sortie de l'usine Lumiere à Lyon, in 1894, which was screened publicly at L'Eden, La Ciotat, a year later. The first public commercial screening of motion pictures took place in Paris on December 28, 1895. The cinematography was also exhibited at the Paris Exposition of 1900. In the exhibition, the films made by the Lumière brothers were projected on a large screen that measured 16 by 21 meters.

According to the theory of retinal persistence, the perceptual process of the brain and the retina of the human eye retains an image for a short period. This theory is the explanation of the illusion of movement that occurs when a series of images are displayed in rapid succession, instead of perceiving each copy of the series.