I am currently trying to broadcast live sporting events, and am having trouble with the settings on my camera. Whenever we point the camera towards the score clock (it's an old score clock, definitely not LCD but we believe it is LED), the numbers stay for a second, get brighter and bolder, and then fade out. The rest of the clock is there, but to viewers it seems as if the clock was turned off.

We have a Panasonic AG-DVX100BP. Using wirecast to broadcast video.

Any ideas of settings we can change to get our video working? All help would be appreciated.

  • don't suppose you can post a short clip on the web somewhere so we can see what it's doing? – cabbey Feb 11 '11 at 21:33

This is the stroboscopic effect. The change from light to dark indicates the shutter speed is not slow enough to capture one refresh cycle in the scoreboard; the relatively slow rate of change indicates some integral multiple of the camera's frame rate is close to the scoreboard's refresh rate. A slight change in your frame rate will only change the speed with which the image seems to fade in and out, but a substantial reduction in your frame rate, such as from 60 to 30 fps, might work fairly well, especially if you can keep the shutter open much longer for each frame. If your slowest shutter speed cannot accommodate at least one entire refresh cycle you might still see a gradual lightening and darkening of the scoreboard but it won't go dark entirely.

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    Frame rate is the likely culprit, but it's more likely the difference between 59.94Hz and 60Hz or between 29.97Hz and 30Hz. It depends whether the clock display refresh is being timed by the mains frequency or an older "TV friendly" crystal oscillator. Either way, the very close frequencies (camera and clock) are going to cause a long strobe cycle, so either turning the SMPTE compatibility ought to do the trick if halving the frame rate doesn't. – user2719 Feb 12 '11 at 4:47
  • That's "either turning the SMPTE timebase compatibility on or off" -- I have no idea what happened to the thought/language interface there... – user2719 Feb 12 '11 at 9:34
  • @Stan Good point. I understand that the AC frequency itself can vary a little, so trying to match it could be a frustrating exercise. Perhaps I'm wrong, though, because I don't know how much or how quickly the frequency varies. – whuber Feb 12 '11 at 15:08
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    Mains frequency is constantly changing, and is a product of supply and demand on the electricity grid. – Rowland Shaw Feb 12 '11 at 16:25

Shutter speed or frame rate come to mind.

Possibly the board is refreshing it's elements at a different speed than the camera is capturing them. The two are out of sync so that you're catching the top of the cycle, then drifting slowly down the curve and eventually you'll make it back up on the next cycle.

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