Recognizing video’s uncanny power to hold people’s attention and keep them engaged for long stretches of time, many live events show “IMAG” video on LED screens on stage or around the venue.
Besides creating a more dynamic experience, LED IMAG video displays make it easier to see the stage, such as close-ups of facial expressions or individual musical performances. And, very often, large LED screens present background graphics or videos that further entertain and inform spectators.
As the use of LED video rises, so too do the problems that can result when these video displays are captured by certain types of cameras shooting the event. If the cameras are among the many popular models designed with CMOS “rolling shutter sensors”, the LED displays they capture on video could be marred by visual artifacts such as:
This extraneous visual noise can wreak havoc on downstream compression engines that are working hard to encode the signal efficiently. Whether the live show is broadcast or streamed, these visual artifacts can detract from the viewers’ enjoyment of the video presentation.
The most common cause of this phenomenon is the mismatch between:
This mismatch occurs because CMOS rolling shutter imagers scan video sequentially line by line from top to bottom. Over the frame time, this acquisition method results in temporal artifacts due to the faster LED refresh rate. In the time it takes a rolling shutter sensor to capture and output one video frame, the LED display has refreshed multiple times. This causes problems like light and dark bands, or banding, across the LED video. People in the venue don’t see this banding or flickering on the IMAG screens. It’s only evident to those watching the video show on their monitors, TVs, or mobile devices. The type and severity of these visual artifacts are determined by the LED screen refresh rate in relation to the simultaneous rolling shutter capture rate.
If you’re thinking about producing video that features or captures LED video screens as part of the show, it’s advisable to conduct tests, or shoot-outs, to determine how your equipment will perform together. So, when evaluating new LED displays and/or cameras, thoroughly test the equipment exactly as you plan to use them before purchasing anything. This is the only way to be sure whether your cameras and LED displays will work together without introducing visual artifacts into your finished product.
In our next blog, we’ll delve into a revolutionary solution—CMOS Global Shutter imaging sensors—that virtually eliminate these visual artifacts that occur when LED video displays are captured by live video cameras.
Advanced global shutter technology is built into two top-of-the-line camera systems by Hitachi Kokusai—the Z-HD5500 and SK-HD1800—both of which provide exceptional imaging quality enabled by full progressive scanned 1080p60 HD, selectable HDR profiles and—with the SK-HD1800, a remote motorized filter wheel—among other high-end capabilities.
To learn more about the challenges of LED video artifacts, such as banding, and how to effectively eliminate this problem, check out our website and Video Gallery where you’ll find many helpful tech tips for producing impressive, pristine imagery for your next video production.