I have seen several videos and I myself filmed couple near the gas station prices and wonder why this happens?
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Digital displays such as LED, VFD and LCD are scanned. The numbers and letters are not on all the time. The computer supervising the display is turning on the LEDs or whatnot at a scan rate faster than the human eye can perceive. This allows the pixels in a display to be a matrix rather than 1:1 controlled. This allows you to control more LEDs than you have control lines for. The refresh rate for this is around 20Hz.
You camera, if it is digital, is also scanning pixels in a similar manner.
Because the display you are looking at and the camera you are using are not synchronized to each other, the LEDs appear to blink from time to time. This is because the camera scans at about 3 times the scan rate of the LEDs. This means that sometimes the camera will be scanning an LED when it is off, but should be on. To your eye the LED stays on all the time. But the camera sees when it is off as well.
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