Quick Look: 2K/4K Recorders for the Canon C500

Quick Look: 2K/4K Recorders for the Canon C500

So you’ve gone and booked a gig with the Canon EOS C500, and you wish to partake of the camera’s detail-rich, uncompressed 2K or raw 4K goodness. You’ll need something to record that on, as the C500 doesn’t capture 2K or 4K internally. The two most common choices for Canon-compatible, uncompressed / raw recorders in the USA market are the Convergent Design Gemini 4:4:4 and the Codex Onboard S. Canon arranged for me and Art Adams to borrow one of each to support my C500 review and Art’s 4K short “A Walk in the Woods”;  here’s a quick look at these two recorders and how you use them with the C500.

Please note: this really is a quick look, not a review: I treated these two recorders as unfamiliar things I had to get working to perform a task, not as objects of deep study and veneration. In other words, I approached them like a data wrangler with a show to record, and this writeup is oriented to that approach: here’s some new gear, you’ve got a gig tomorrow, so what do you need to know?

Convergent Design Gemini 4:4:4

Convergent Design has been building solid, functional products since the days when a DV-to-SDI encoder/decoder was a Big Deal. The Gemini 4:4:4 has the spartan, non-nonsense, utilitarian aesthetics of other C-D products: it looks like a mil-spec onboard monitor. The Gemini is a flat, metal, dark-gray box with a 5”, 800×480 IPS LCD on the front, slots for dual 1.8” SSDs on the top, and dual 3G SDI inputs on the bottom, along with HDMI and SDI monitoring ports, a 3.5mm headphone jack, and a 3.5mm auxiliary audio input.

Gemini runs on 6 to 19 Volts DC and draws 8 to 16 watts. It’s supplied with a 4-pin XLR power cables, as well as an AC adapter. Our loaner production kit also included a D-Tap connector and a 14.4 volt, four-cell Li-Ion battery pack, which looked for all the world like a radio-controlled car battery, with a simple bent-metal holder mounted on the back of the recorder. Whichever powering option you choose, its cable plugs into a Hirose connector on the underside of the recorder. That plug is the power switch; there’s no separate button to turn the Gemini on or off.

The recorder is 138 x 120 x 37mm (5.4 x 4.7 x 1.5 inches) and maybe 0.9 kilogram (two pounds) fully loaded with two SSDs and the battery pack.

The casing is uncluttered with buttons and switches; instead a resistive touchscreen overlay (think Palm Pilot, right down to the supplied stylus) gives you access to the Gemini’s menus and options. Surprisingly, the Gemini lacks a slot or clip to hold the stylus. I wound up wedging it (very gently!) between the battery and its holder. Without the battery and holder, I don’t know where I would have stored the stylus; I suspect a lot of them wind up being Velcroed to the side of the recorder.

Three bright, multicolor LEDs show you drive and system status at a glance. Three colors predominate: green for ready, red for recording, and blue for playback. The two drive LEDs use other colors—orange, purple, aqua, white, and yellow—to indicate other conditions; fortunately the user manual includes a lookup table so you can easily match colors to their meanings.

Gemini recording 2K, so only SSD1 is in record mode.

The Gemini has a single 1/4” tapped mounting hole at its base and comes with a screw-in tilt-and-swivel shoe mount. I used that mount to stick the Gemini on the accessory shoe of the C500‘s top handle. I was a bit nervous about balancing $7500 worth of recorder on a small and seemingly flimsy shoe mount (OK, rather more than a bit). Nonetheless the Gemini stayed securely in place through whatever casually negligent handling Art Adams and I subjected it to, with the camera moving between tripod, slider and running-through-the-woods handheld use (Convergent Design suggests using a Noga arm or a third-party side mount adapter as alternatives to the shoe mount).

1st AC Ted Allen and DP Art Adams capture "A Walk in the Woods" with the Gemini shoe-mounted on the C500.

Out of the box, Gemini records HD and 2K DPX files; upgrades allow ARRIRAW, C500 4K raw, and 3D recording. A Canon raw 4K-capable Gemini runs about $7500 (including two free 512GB SSDs during a current promotion; these are normally about $1500 each). The recorder comes in a Pelican-style case with the XLR power cable, an SSD transfer station (eSATA, with a USB 3 adapter), SDI and HDMI cables, shoe mount, and AC supply.

At present, the Gemini doesn’t handle every possible permutation of bit depths, image sizes, and frame rates the C500 outputs, with some of the higher frame rates and more exotic modes (like 12-bit 2K and various overcrank/undercrank speeds) either not supported or requiring two Geminis. Up-to-date details are available on the Gemini product page; anything I write here will likely be outdated by the time you read it, as Convergent Design frequently updates the firmware to support new speeds ‘n’ feeds. We shot 10-bit 2K and HD, and raw 4K and QuadHD, at 24fps, as well as half-raw 4K at 60fps; the Gemini happily recorded those formats, so we were all set.

A single SDI cable connects the Gemini to the C500, and that’s it: data, metadata, and control flow across 3G SDI from camera to recorder (the C500 uses dual-link 3G-SDI for frame rates over 30 fps, but you’ll need dual Geminis to record ’em). Once the Gemini is set to Canon Raw mode and camera triggering is enabled, no additional intervention is required. Shooting with the tethered Gemini requires no extra effort aside from monitoring battery level and available recording space. When Art Adams shot “A Walk in the Woods”, my role as data wrangler consisted of making sure all three LEDs lit up red when the camera was rolling, and occasionally playing back a 4K clip on the 5” monitor to make sure that recording was proceeding properly. The single onboard battery held up fine for three powered-up hours of monitoring and occasional recording; the camera ran down its battery faster. (Convergent Design says the battery will last for 8 hours of standby monitoring, or  2.5 – 4 hours of actual recording.)

4K data are recorded across two 512 GB SSDs, with even frames on one SSD and odd frames on the other. About an hour of 24fps 4K can be recorded on the pair. When recording 10-bit DPX files (HD or 2K) at normal frame rates, only one SSD is used.

Operationally, the Gemini is a fine performer, disk formatting aside. The recorder boots up in about 12 seconds, and is then ready to roll… but formatting the drives, which is the only way to erase clips, takes 60 seconds each (with 512GB SSDs).

About 2/3 of the way through formatting SSD2

Menus are shallow, straightforward, and easy to navigate. The only critical setup issues are choosing between DPX and Canon raw modes, and deciding whether to let the camera control recording. You should also set up the file naming convention (though if the C500 is recording proxies to CF cards, the Gemini will automatically use the same clip name; full details in Convergent Design’s C500 quick start guide), and set metadata—Reel, Scene, Take, Camera, Project, and Day—to help the folks in post, but the recorder doesn’t require these.

The screen shows the entire frame by default, but it also lets you zoom in 1:1 for critical viewing. You can play back clips onscreen (even Canon raw gets deBayered and played in real time). You can connect an external display with SDI (and with HDMI in a future firmware version), but having the built-in monitor means you don’t need a separate display when you’re traveling light.

Data wrangling is done with a small transfer station, connectable to Mac or PC via Thunderbolt, FireWire800, or USB 3.0 depending on the adapter used.

Transfer Station with a Seagate GoFlex Thunderbolt adapter. Upper cable is for the power supply.

The transfer station adapts the 1.8” Convergent Design SSDs to a standard 2.5” eSATA interface. Seagate GoFlex sleds and adapters provide the conversion to Thunderbolt, FireWire800 or USB 3.0.

Convergent Design says they see 325 MB/sec transfer rates with a single Thunderbolt port to a Pegasus RAID; 375 MB/sec with a dual port hookup. I only did small transfers to my MacBook’s internal HD, so I can’t say much beyond that observation that if you want to play with 2K uncompressed or 4K raw footage, you really do want to have fast and capacious storage available.

Convergent Design’s GeminiTransfer utility moves clips from the SSDs onto backup storage. It’s a cross-platform Java program; it’s functional, if not elegant. Using GeminiTransfer instead of Finder (or Windows Explorer) copies is recommended, especially since certain Gemini DPX recording modes “pack” the data on the SSDs, and GeminiTransfer knows how to unpack the data into standard DPX files.

GeminiClipMerger is a similarly minimalist program that interleaves the data from the two SSDs into folders containing entire 4K clips.

In my C500 testing, I switched formats with wild abandon, recording HD, 2K, QuadHD, 4K, and 4K half-raw files one after the other. The Gemini handled it all with ease, though on occasion a frame-size or format change confused the recorder; it would plaintively state “Format not supported” until I power-cycled it. When it came time to transfer the mix of 2K and 4K clips, and merge the 4K clips together, it all Just Worked: Data Transfer and Clip Merger happily sorted through the mess I’d made on the SSDs and properly segregated the reassembled 4K clips in their own directory.

Convergent Design frequently tweaks the firmware of the recorder. When I started testing it, it was running build 1.4.101, and it recorded 2K and 4K with no problems aside from the occasional momentary confusion when I switched image sizes on the camera, and a visual glitch recording 4096×2160 clips (3840×2160 clips and 2K clips were fine). For Art’s shoot, we upgraded to 1.5.146, which fixed the 4096-wide issue, and changed the way files are closed and SSDs dismounted to reduce the chance of data loss if a power failure occurred or an SSD was yanked out accidentally.

This build worked perfectly well, and didn’t get confused when I switched image sizes on the camera.

On the very last day I had the Gemini, I switched it back to 2K to show it off to some folks, and the Gemini cycled itself in and out of record without waiting for the camera trigger. A quick query with the always-vigilant and unfailingly helpful Dan Keaton at Convergent Design (he’s their director of sales and marketing and the de facto front-line support guru; it is rumored that he never sleeps) revealed that 1.5.146 didn’t like having user bits set to time-of-day on the C500. No worries; we could simply have turned off user bits on the C500, or rolled back to the previous build had we needed to; as I write this there are eight different firmware versions available for download.

Overall, the Gemini is a very task-focused device. It has a compact and lightweight form factor, low power requirements, a large and useful touchscreen monitor, and a flexible transfer station. It may not win any industrial design awards, and the website and documentation aren’t always completely in sync with the current firmware’s capabilities, but the documentation is comprehensive and thorough, well formatted for field use on an e-Reader like an iPad, and the support is highly responsive and helpful.

And in our use, the Gemini just worked. Really, for a recorder, isn’t that what counts?


Next:  Codex Onboard S Plus…

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About The Author

Adam Wilt

Adam Wilt is a software developer, engineering consultant, and freelance film & video tech. He’s had small jobs on big productions (PA, “Star Trek: The Motion Picture”, Dir. Robert Wise), big jobs on small productions (DP, “Maelstrom”, Dir. Rob Nilsson), and has worked camera, sound, vfx, and editing gigs on shorts, PSAs, docs, music vids, and indie features. He started his website on the DV format, adamwilt.com/DV.html, about the same time Chris Hurd created the XL1 Watchdog, and participated in DVInfo.net‘s 2006 “Texas Shootout.” He has written for DV Magazine and ProVideoCoalition.com, taught courses at DV Expo, and given presentations at NAB, IBC, and Cine Gear Expo. When he’s not doing contract engineering or working on apps like Cine Meter II, he’s probably exploring new cameras, just because cameras are fun.

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