How ClearVid Sensors Get Max Sensitivity in a Min Space

Yes, the new HVR-V1U camcorder is Sony’s first 24p Handycam-style HDV offering, and it only costs $4800. Whether you’re a DIY filmmaker or you’re just in need of a high-quality but relatively disposable camera to grab risky footage, that’s good news. But at a press event last week launching the V1U, Sony shared some more technical news that revealed a little bit more about its small-format acquisition strategy. Here’s a look at Sony’s new CMOS technology and an explanation of why you won’t see Sony pro cameras using AVC compression any time soon.
The HVR-V1U is slated to ship in December, with a $4800 MSRP described as “tentative” (it’s not likely the price will go up, given that Sony wants badly to describe this as a “sub-$5000 24p HDV camcorder”). Among the planned accessories are the VCL-HG0862K wide-angle adapter, the SH-L35WBP LCD Hood, the HVL-LBP light (due in February), the RM-BP1 tripod remote control and, best of all, the HVR-DR60 hard-disk recorder, which integrates closely with the V1U, allowing disk status to be checked on the camera’s LCD screen.
First, the three ¼-inch (that’s not a typo) CMOS sensors built into this camera are a new kind of animal. The technology, dubbed ClearVid, is designed to improve the resolution vs. sensitivity equation that can dog small, high-resolution sensors – as you cram more, smaller pixels into a tinier sensor chip, the light-sensitivity of each of those pixels suffers, and so does your available dynamic range. The ClearVid sensor addresses this by rotating the photosensitive pixels by 45 degrees, creating a diamond-shaped layout of pixels that can each be somewhat larger than their conventional counterparts. By increasing the area of each pixel, sensitivity is maximized in the space available to the chip.

Confused? Check out the promotional video Sony made to tout the new sensors.

The pixel resolution of each ClearVid sensor is 960×1080, and the horizontal resolution of the acquired image is doubled by using the corners of the diamond pixel pattern – where the photodiodes come closest to touching at their points – to interpolate the picture to a full 1920x1080p 4:2:2 image. (Image processing takes place at this resolution.) Because of the limitations of the HDV format, that image is then subsampled to 1440x1080i, and finally converted to 4:2:0 color space for HDV compression. The 24-frame image is recorded to the 60-frame HDV stream using a 3:2 cadence. (Unfortunately, there was no mention of ways to get at the image in either full resolution or in its native color space, but that seems like a possibility in future implementations of the ClearVid technology.) Sony says "leading NLE manufacturers" are "scheduled" to update their systems to handle Sony's 24p scan mode.

And the other tech news from Sony’s briefing was a definitive statement about its stance on AVC encoding. AVCHD emerged earlier this year as a consumer HD-recording format being championed by Sony together with Panasonic, and Panasonic has been making some noise since NAB 2006 about a pro variant of AVC encoding that would enable a higher recording capacity for HD on P2 cards. The obvious question was whether Sony also intended to introduce AVC recording for its pro and prosumer cameras, including HDV models as well as, perhaps, the MPEG-2-based XDCAM HD.

Hugo Gaggioni, chief technology officer for Sony Broadcast and Production Systems, was complimentary of AVC technology in general, but told attendees Sony would stick with existing MPEG-2 solutions while waiting for interframe AVC to mature – specifically as far as single-chip implementation. He did say that he expects AVC to reach that maturity faster than MPEG-2.

“Today we feel MPEG-2 long-GOP [encoding] is at its highest profile in size, power-performance, and picture quality,” Gaggioni said. “We are completely behind AVC. It is a superior algorithm, but very complex. It is just beginning to be implemented in a single IC. AVC is making inroads in boards and big boxes, not single-chip solutions. We will reach the same level of maturity [with AVC codecs], but we don’t see it right now.”

NAB 2008, maybe?

Discuss this story at the StudioDaily forums.