Moving pictures

Moving images are called a sequence of images which, by displaying them at short time intervals using suitable technology, create the illusion of movement for the viewer . Usually the term is used synonymously with " film images ". For human perception , around 16 to 18 images per second are sufficient to create the illusion of flowing movement, provided that the individual images differ only slightly from one another.

history

Octagonal mirror top for the playful representation of a moving horse with rider

The invention of moving images (motion pictures) is based on presenting series of images or snapshots in natural sequence (1, 2, 3, 4, 5). The first “moving images” were technical advancements in flip books , such as the phenakistiscope , the zoetrope or the praxinoscope . With the electrotachyscope , the possibility of enlarged wall projection , they finally led to film .

principle

The photographs themselves or an image carrier are seen standing still. One speaks of interrupted or intermittent transport in connection with a shutter during recording or a shutter during playback. There is a dark pause between the momentary or phase images . In the conventional film camera , a so-called cycle is divided into two parts, which are expressed by the complementary angles in the circular rotary shutter , for example 190 degrees transport dark phase and 170 degrees exposure or lighting phase.

Two peculiarities of the human sense of sight contribute significantly to a realistic perception: First of all, the image frequency must be above the flicker fusion frequency for flicker-free perception . The actual perception of movement arises from relatively minor differences in the content of successive images, which are interpreted in the brain as a change in position and thus as movement. This effect is called stroboscopic motion or beta motion.

Flicker-free display is possible from about 45 light-dark changes per second, at which most people only perceive the flicker unconsciously. However, very bright and high-contrast images can still lead to flickering here. After viewing moving images for a long time, this can become noticeable through eye fatigue or headaches. From around 60 light-dark changes per second, the risk of such effects is largely eliminated. A method with 60 images per second is showscan .

Basic technique

In order not to actually have to record 50 or 100 individual images per second, the trick was used early on in film to play back each of the recorded images several times. 16 ( phase ) images per second are displayed when using a three-wing screen or a three-way rotating screen with 48 light-dark changes. With the help of a two-wing screen, 48 images are projected from 24 film images recorded per second, the image frequency of the sound film, which is a compromise between jitter-free display, minimal material consumption and a presentation that is perceived as flicker-free.

In the case of video and television, the European PAL and SECAM methods show 25 frames or 50 fields per second, as this corresponds to the AC frequency of 50 Hertz that is common in European power grids .

In addition to the simplex method described so far, there is the duplex method .

There are various techniques for playing back moving images. The most important are:

Plasma, liquid crystal screens and OLEDs are not affected by flicker due to the way they work.

If sounds are also reproduced at the same time as the moving images, then this is an audiovisual sequence .

Timetable

from 1600: Flip book - flip book with individual images
from 1671: Laterna magica - magic lantern: early device for image projection
from 1825: Thaumatrop - miracle disc with two threads
from 1830: Phenakistiskop - phantascope, miracle wheel or wheel of life

from 1832: stroboscope - magic disks: flash unit

from 1834: Zoetrop - miracle drum with slots

from 1861: Mutoskop - stereo animation sheets per stroboscope

from 1877: Praxinoscope - electrical high-speed viewer using a mirror arrangement

from 1879: Zoopraxiskop - projection device for chronophotographically generated serial images

from 1880: Kaiserpanorama - popular mass medium with stereoscopic picture series

from 1886: Electrotachyscope - projection device for row images

from 1891: Kinetoskop - first film viewer

Individual evidence

^ E. Bruce Goldstein: Encyclopedia of Perception. Volume 1, Sage Publications, Thousand Oaks 2010, ISBN 1412940818 , p. 458 ( online ).
↑ Bill Nichols, Susan J. Lederman: Flicker and Motion in Film. In: Teresa DeLauretis, Stephen Heath: Cinematic Apparatus. Springer, London 1980, pp. 96-105 ( Google books ).

[Goldstein2010-1] E. Bruce Goldstein: Encyclopedia of Perception. Volume 1, Sage Publications, Thousand Oaks 2010, ISBN 1412940818 , p. 458 ( online ).

[Nichols1980-2] Bill Nichols, Susan J. Lederman: Flicker and Motion in Film. In: Teresa DeLauretis, Stephen Heath: Cinematic Apparatus. Springer, London 1980, pp. 96-105 ( Google books ).