Sunday, 30 January 2011
Why does the series of images appear to be moving?
Spin the zoetrope and look in through the small slits. You can also design and draw your own animation and see if it works.
The pictures begin to come to life; they appear like a short film. You will also note that the zoetrope’s story is looped; it always ends in the same image from which it began.
You see a series of consecutive images divided by black framing. When the consecutive images follow each other closely, your brain perceives the images as a continuous motion, even though each image presents one individual still picture. The black surface between the slits corresponds to a film projector’s shutter; while the machinery shifts the image from one frame to the next, the shutter obscures this event. Therefore, the images flow in front of your eyes as a seemingly continuous stream.
The zoetrope was developed in 1834 by Englishman William Horner, who originally called it a Daedalum. In 1867, Frenchman Pierre Desvignes introduced it to the market with its new name, zoetrope, a wheel of life.
Film projectors present images at a speed of 24 frames per second. A long film is, in reality, truly long, approximately 2.5 kilometres of film. Within the European PAL system, a digital television image can be changed 25 times per second. The jerky effect of these changes can be reduced by changing the image in an interlocking fashion, in other words, by moving a half frame at a time. This can be accomplished at a doubled rate of 50 times per second.