Stroboscopic Effect

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Stroboscopic Effect


an illusion of apparent motion or absence of motion that arises when an object or picture is viewed not continuously but during separate time intervals that succeed one another in a periodic manner. An example is the projection of a picture on a screen through a shutter consisting of a rotating disk with slits that alternately passes and shuts off the projecting light. Another example is the illumination of a dark room by periodic flashes of light.

Stroboscopic effects are a result of persistence of vision—that is, the retention in the viewer’s consciousness of a perceived visual image for a short time after the picture or object producing the image disappears. If the time between successive intervals when the picture or object is viewed is shorter than the visual-persistence time, then the images resulting from the discrete acts of viewing are fused into a single image, and the viewer thinks he continuously sees the picture or object.

Two types of stroboscopic effects may be distinguished. In one type, an illusion of apparent motion results when separate pictures are viewed intermittently and the positions of the objects in each picture are slightly shifted relative to the positions in the preceding picture. This type of stroboscopic effect is responsible for the perception of motion in motion pictures and television.

In the second type of stroboscopic effect, an illusion of apparent lack of motion or of slowed motion occurs when a moving object periodically, with the frequency f1, takes up a previous position. For the object to appear to be totally still, the frequency f of the moments when it is viewed must be equal to f1 If f and f1 are not equal but differ by a small amount, then the frequency of the apparent motion of the object is fft. In this case, the apparent motion may be much slower than the actual motion and may differ from it in direction. The instruments used to achieve this type of stroboscopic effect are known as stroboscopes.


References in periodicals archive ?
To quantify the stroboscopic effect first of all it is necessary to define photometric flicker quantities.
The detection of stroboscopic effect (percent likelihood of detection d, in percent) for rectangular waveforms operated so that the maximum light output is produced 50% of the time and the minimum light output is produced 50% of the time (50% duty cycle), has been described in [7] by the equation
Different kind of amplitude mode light regulation techniques have been considered previously in [13]--[15], however the stroboscopic effect usually is insignificant for these regulation approaches.
Pulse mode light regulation technique is the most interesting from the point of view of stroboscopic effect.
This method allows to increase efficacy of dimming process as well as to reduce stroboscopic effect.
The stroboscopic effect also can be reduced by using of several LED matrices with interleaved control signals [18] as shown in Fig.
The relationship between the percent flicker (flicker index), flicker frequency and the acceptability of stroboscopic effect is given in [7].
The similar relationship for percent likelihood of detection of stroboscopic effect is also given in [7].
7 it was found conditions to accomplish acceptable level of stroboscopic effect in whole regulation range: operation frequency above 1.
The luminous flux of LED follows the forward current (voltage) at very high speed [6] making possible undesired stroboscopic effects under certain conditions (considered in the following sections).
Most of McLaren's animated work, like the jazzy Begone Dull Care, was drawn directly on to the film, but he also used "cut-outs" of shapes, traditional cartoon elements, and in the lyrical Pas de Deux, stroboscopic effects.