I recently appeared on my local TV station. When I arrived at the studio I was asked to change my shirt because its pattern would look distorted on screen. What causes this effect and why, in this day and age, is it impossible for television to record what is in front of the camera? (Continued)
An earlier answer to this question (19 May) suggested that wagon wheels appear to go backwards in movies and on TV due to the finite horizontal resolution of the camera/TV system. In fact, this illusion is caused by the strobing effect of the frame rate. Essentially, each frame (25 or 30 per second depending on the country) takes a snapshot of the position of the spokes and if the rate of movement of the wheel is such that the next spoke in turn hasn鈥檛 reached the position of the previous spoke by the time the next frame is taken the brain will perceive a reverse rotation.
Max Dirnberger, Senior Electronics Engineer, Mount Waverley, Victoria, Australia
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