Before we continue, I think it's a good idea to break down what exactly 4K video is, at least in terms of resolution. With different cameras offering different resolution modes, this can get confusing. 4K actually has two different standards associated with it: a Digital Cinema standard and a Broadcast standard. The Digital Cinema standard specified by SMPTE has 4K at a resolution of 4096x2160. That's two times taller than standard 1080 HD video and a little more than twice as wide, meaning that the DCI standard has a 1.89:1 aspect ratio for cinema use. The Broadcast standard is 3840x2160, which is exactly twice as tall and twice as wide as standard 1920x1080. We often call this Quad HD instead of 4K. The broadcast resolution is lower than the DCI standard to maintain the 16x9 aspect ratio (1.79:1) we use today. This means HD can be scaled evenly on a 4K TV, which keeps the monitor-panel manufacturers happy. You can imagine that it's much easier to combine four HD panels into one TV versus making a whole new design with a wider aspect ratio.
So, those are the standard 4K resolutions; now we have to talk about how 4K gets from a source to a display. There are standards for both the professional Serial Digital Interface (SDI) and the consumer HDMI connections. In the pro world, SDI is still king, but regular HD-SDI only supports resolutions up to 1920x1080. To get to 2K, we need two times that bandwidth, even though the 2K resolution is just a bit larger at 2048x1080, so Dual Link or 3G-SDI can handle this resolution in full 4:4:4 color sampling. To get to 4K video, though, we either can combine two 3G-SDI connections for 4:2:2 color sampling or four 3G-SDI connections for 4:4:4. If you were working in Dual Link connections, this would be a whopping eight SDI connections. That's a whole lot of SDI. Look for a 10G SDI standard in the future, which should cover all of our 4K and high-resolution needs. HDMI, on the other hand, has been upping their standards to support 4K. The HDMI 1.4 specifications support 4K video on one cable, either in 3840x2160 or 4096x2160 formats. This is definitely good news for the consumer.
The [Canon EOS] C500 can output, via 3G-SDIs, either 4096x2160 (4K) video or Quad HD raw data.
Going back to the original problem, our customer wanted to be able to shoot 4K and then play back his content immediately. For all the reasons explained above, this is still a difficult process. As of early this year, there really was only one solution for this, which was to use a RED camera (ONE, EPIC or SCARLET), download the footage into your computer and then use the RED Rocket computer card to play back the footage. Our client was looking for something a little simpler, so I suggested the new Canon EOS C500 and its companion recorder from AJA, the Ki Pro Quad. The C500 can output, via 3G-SDIs, either 4096x2160 (4K) video or Quad HD RAW data. The client would be able to take a 4K feed from the camera through the Ki Pro Quad into his projector and thus get 4K live. This does require an additional converter, though. His projector takes the HDMI 1.4 connection, and Blackmagic Design has just released a new SDI-to-HDMI 4K converter.
The C500 doesn't record 4K inter-nally, however, just a reference HD recording. So for 4K recording, we need an external recorder like the Ki Pro Quad. The new Ki Pro can take the RAW output from the C500, convert it to video internally and record it in ProRes 10-bit at 4K resolution. The Ki Pro Quad has SDI outputs for 4K monitoring or monitoring in HD. Also, the original RAW data can be sent to a computer via the built-in Thunderbolt connector. Other great recorders like the Codex S and Gemini 444 will be able to record the RAW signal from the camera directly. I believe a considerable segment of the market will just want the 4K video that the Ki Pro Quad records. The C500 and Ki Pro Quad combo also will record 2K in 12-bit 4:4:4, which no doubt will be a popular option, too. And, of course, the C500 has Canon Log mode, providing a wide dynamic range.
This was the ticket for our 4K projecting client. He wanted to be able to record and play back 4K, and that's just what the C500 offers. He went ahead and put in an order for the Canon C500 and the AJA Ki Pro Quad. The wave of 4K video cameras will no doubt con-tinue, and, to me, this really signifies the arrival of 4K acquisition.
Andy Shipsides is a N.Y.-based Camera Technology Specialist and Manager of AbelCine's Training Department. To learn more about AbelCine's Understanding HD Series, visit training.abelcine.com.
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