SMPTE 2015: Challenges of Adding HDR, HFR and Color to 4K

At the SMPTE 2015 annual conference, broadcast consultant Jim DeFilippis, Grass Valley camera executive Klaus Weber, and Panasonic researcher Hiroaki Iwasaki, among others, looked at the challenges involved with adding higher frame rates, higher dynamic range and wider color gamut for 4K resolution and beyond. Baylor University professors Corey Carbonara and Michael Korpi attempted to find the perfect amount of frame rates, exposure times, lighting, and refresh rates to arrive at the best image.

TV Technology reports the challenges inherent in wanting it all. “The higher one goes up in frame rate, the less the exposure time, but with a longer exposure time, it will be more blurry,” said DeFilippis. “Shorter exposure time is less motion blur and more judder and strobing.”

videostreamIn experiments developed with ESPN, DeFilippis, Carbonara and Korpi discovered that HFR introduced a sensitivity loss requiring more light, and shorter exposure times presented strobing problems.

The team also learned that outdoor light levels were not a factor in frame rate or shutter angle, but indoor light levels “were critical at higher frame rate and short shutter angles.” The conclusion is that “shooting at higher frame rates takes some planning in the way of post, lighting and shutter angle;” motion compensation can be used to convert to lower frame rates, and variable frame rates can be a new storytelling tool.

Weber, examining colorimetry, sensitivity, resolution, high frame rates and HDR, reported that, “HDR likely will provide the most bang for the buck, with peak brightness as much as 10,000 nits (versus a standard TV’s 300). He also said that CMOS imagers (used in most newer cameras) are capable of “huge dynamic range,” proven in trials across Europe during which HDR cameras produced “almost perfect” images at 800-percent overexposure.

Iwasaki, who does lighting application research, studies color reproduction under various types of lighting, especially LEDs. With the use of LEDs in TV production increasing, he found that the most commonly used LED lighting (yellow phospher-converted blue LEDs) had lower color rendering, but higher luminosity. Red and green phospher blue LEDs generated both high luminosity and color rendering. Even under LED lights, he concluded, “the color reproduction of 4K cameras is more accurate than that of HD cameras.”