Why does an LED score clock fade in and out on video, and how can I fix it?
Asked 2/11/2011
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2 answers
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I’m live-streaming sports with a Panasonic AG-DVX100BP and Wirecast. When the camera points at an older electronic score clock (likely LED, not LCD), the digits appear normally for a moment, then get brighter/bolder and eventually seem to disappear, even though the rest of the clock remains visible. What camera settings should I change to make the clock readable on video?
Originally by user3827. Source · Licensed CC BY-SA 4.0
user3827
15y ago
2 Answers
12
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.
Originally by user1356. Source · Licensed CC BY-SA 4.0
user1356
15y ago
0
Generated from our catalog & community — verify before relying on it.
This is usually caused by the scoreboard’s refresh cycle fighting with your camera’s shutter/frame rate. The camera is sampling the LED display out of sync, so the digits drift from bright to dim and can appear to vanish.
The main fixes are:
- lower the shutter speed so each frame captures more of the display’s refresh cycle
- try a different frame rate; a bigger change can help more than a tiny one
- if you’re at 60 fps, test 30 fps and use the longest practical shutter time
A small frame-rate change may only change how fast the fading happens. A larger change, combined with a slower shutter, can reduce or eliminate the dropout. If your shutter still isn’t long enough to capture a full refresh cycle, you may still see some pulsing, but it should be less likely to go completely dark.
In short: experiment with slower shutter speeds and alternate frame rates until the display stays stable.
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