NAB 2015: Notes From the Floor on Three-Sensor 4K Cameras

LAS VEGAS—At the 2014 NAB, Grass Valley dropped a bombshell when it introduced a three-sensor 4K camera, left, employing 2/3-inch CMOS chips, referred to as B4 mount. Sports and other stadium events telecast production companies had been demanding such cameras, and last year’s Grass Valley product set off a race among other camera makers.

Wanderers on the 2015 NAB show floor will see B4 mount 2/3-inch 4K cameras, not only from Grass Valley, but from Hitachi, Ikegami and Sony (on the tripod below). Canon and Fujifilm both have new families of lenses for these cameras.

The reasons these mobile truck and large venue broadcast companies wanted the 2/3-inch chip cameras instead of single Super 35mm sensor cameras, known as PL mounts, actually has more to do with the lenses than the cameras themselves. There are a couple of rules of optical physics at work here.

First, the larger the sensor is, the larger the lens. PL mount, long zoom range lenses that could replicate the fields of view that today’s B4 mount HD lenses do for outdoor broadcast would have the form factor of a World War II howitzer.

This is obviously not good.

The second problem these large sensor PL mount lenses present is that their depth of field for any lens setting is much shallower than for these same lens setting for a B4 mount 2/3-inch three-sensor camera. That shallow depth of field may be all the rage in Hollywood, but it would make the sports camera operator’s job of staying in focus a much more difficult task.

Further, when fans are watching a live action sporting event on TV, they’re used to more than just the player with the ball being in focus. They are accustomed to a greater depth of field.

In talking with representative from both lens companies, they explained that their prior top-of-the-line HD lenses actually were hitting 4K specs in the center of the lenses, but needed improvement in the corners. Their new products meet those corner specs.

When most people think of 4K they relate to it in terms of resolution, twice as many lines of horizontal and vertical resolution. But there’s also a greater color space in the 4K spec, and this, too, had to be addressed in the new 4K lenses. When one of these new 4K lenses is mounted on one of today’s HD cameras, the image is noticeably better.

The race to fill the upcoming 4K needs of outside broadcasters has just gotten started.