Timecode vs. Genlock: Why timecode may not be enough to keep your set in sync

By Henri Rapp

The common assumption is that by feeding timecode to camera you will keep camera and sound in sync. Unfortunately this is not so, Timecode and Sync are not the same thing. Timecode is in fact only metadata to identify how the first frame is labeled for time when the camera begins rolling. Once a camera starts recording, it ignores external timecode and uses its own internal clock to record. The problem you get here is the camera clock is not calibrated to the external sound recorder’s clock, and slowly they will drift apart as you continue to record. This is especially problematic for productions that require a long roll time (30 minutes plus), such as Reality TV or Event Coverage. This can cause endless headaches in post when you match the audio and video with timecode, and by the end of the clip the video is noticeably out of sync with the audio. The solution here is Genlock.

What is Genlock?

Genlock originated in the early days of broadcast and video switching systems. Genlock was used to keep cameras, and other video sources’ frames in sync to avoid nasty artifacts introduced when switching from one source to another. These days most switchers can compensate for this rather than feeding black burst to every source from a central clock. In the HD world Genlock is still hanging around, but these days it uses a protocol called Tri-Level Sync to clock both the frame rate and line rate. This is especially important for 3D two camera rigs. Because Genlock clocks the capturing of frames on a camera, it can be used to keep the picture from drifting from the audio over time.

Keeping Set in Sync with Timecode, Genlock, & Word Clock

In order to keep every device in sync, you need to have everything clocked by one central master clock. The cameras need to be fed timecode and genlock, and the audio recorder needs timecode and word clock. I decided for my rig to use Timecode Systems :Wave Master Clock. This acts as a generator for Word Clock & Genlock and is slaved to my Sound Devices 664 for Timecode. With an additional 9 pin Lemo to USB data cable, I am able to control metadata, arm and disarm tracks, start and stop recording, and more on my Sound Devices recorder. The Timecode Systems UltraSync Ones get rejammed twice per second via 865 MHz to 923 MHz Worldwide ISM bands. Each camera gets an UltraSync One that outputs timecode and genlock keeping the camera perfectly in sync with everything else on set.

Common Cameras That Can Be Genlocked

Here is a few examples of commonly used cameras that can be Genlocked (Some, like the FS7 for example, require additional accessories to take Genlock and Timecode):

Arri: Arri Amira, Arri Alexa, Arri Alexa Mini

RED Digital Cinema: Red Weapon, Red Epic, Red Scarlet, & Red Raven

Sony: Sony FS7, Sony F5, Sony F55, & Sony F65

Canon: Canon C700, Canon C500, Canon C300 Mark II, & Canon C300 Mark I

Panasonic: Panasonic HPX-2000, Panasonic HPX-250, Panasonic P2HD, Panasonic Varicam 35

About The Author:

Henri Rapp is a Location Sound Recordist & Recording Studio Engineer in Cleveland, Ohio. When not out in the field I also do audio post-production for video and produce music out of Bad Racket Recording Studio in Cleveland.

Canon C300 users looking to enter the new 4K world while still retaining the look and feel of their original C300 will appreciate the advances that the EOS C300 Mark II brings to the table. And users who may have struggled to cobble together a rig for their C300’s will particularly appreciate the Canon C300 Mark II ENG Package, which combines the camera with a Zacuto ENG rig, Zacuto Gratical viewfinder and Canon Cine-Servo 17-120 T2.95-3.9 EF lens.

FEATURES

Since its inception, the C300has been a favorite of run and gun documentary, reality, event and sports videographers looking for Super35 sensor versatility in an easy to operate package. Its MPEG-2 8 bit 4:2:2 MXF-wrapped files were perfectly suited to broadcast workflows and formats. Yet most traditional shooters had to acclimate themselves to different control positions and an entirely different ergonomic construction.

C300 Mark II

The C300 Mark II retains the same form factor and basic operational controls as the C300, but brings the camera into the new world of 4K/UHD acquisition with internal bit depths up to 12K and color sampling up to RGB 4:4:4 while also adding RAW output to external recorders.

The same rigging issues, though, remain. In order to create a versatile, sturdy package, Canon partnered with Zacuto to bundle its ENG rig and Gratical viewfinder, topped off with the 17-120 Cine Zoom lens to create a total ENG/EFP package.

Zacuto has long been known for its sturdy construction, adaptability with every from of z-connector you could imagine, and in more recent years its electronics.

We’ll start with the rig itself and then move to the camera.

The ENG rig is based around Zacuto’s Pro Baseplate, a universal plate with VCT wedge and tailhook, a very comfortable shoulder pad, holes for front and rear 15mm LWS rods, and horizontal vertical adjustment. It then adds a lens support (essential for a heavy Cine lens and honestly, I even believe in lens support for heavier still lenses), quick release mount for the C300 AV unit, a helmet kit including handle, cheeseplate helmet and rail. Add the Zacuto Axis Mini mounting arm for the Gratical and you’ve got the front and top of the rig. On the rear it mounts a cheesebox, plates for wireless mics, and a V-mount battery plate with both d-tap and Lemo connectors. It adds all necessary power connectors for camera, Gratical, and Cine-Servo lens. My test unit arrived with the C300 AV unit mounted on the rear of the camera, as Zacuto shows it on their website and introductory video.

Zacuto knows how to engineer and build. Zacuto knows all about camera balance. The completed unit balanced perfectly on my shoulder hands-free. We camera folks know that’s the goal. Zacuto’s promo video holds up an old Betacam unit to show this contraption is about the same size.

But on the down side, all of this engineering comes at the price of weight. By my scale, the camera plus rig plus a 150w battery came in at 19.5 pounds. That’s without lens and without counterbalance. The Canon Cine-Zoom with the servo unit weighs around 6 pounds. A deal-breaker for some while for others a reminder of days gone by.

The Zacuto Gratical viewfinder is in my assessment the best third party electronic viewfinder on the market. With a 5.4 million pixel OLED display resolving 1280x1024 its image is unsurpassed. It is weather resistant, multi I/O (HDMI and SDI) and infinitely mountable. With peaking, false color, zebras, scopes and even cross convert on output, it has every imaginable viewfinder option. Most significant for this camera though is its ability to import viewing LUTs. Many shooters in the LOG realm prefer to expose viewing through a LUT rather than attempting exposure of the LOG material. While this is often a matter of personal skills and preferences, at least the ability to apply a LUT in viewfinder is attractive. It can be particularly attractive if for whatever reason the operator chooses not to output a display LUT from the camera.

The 17-20 Canon Cine Zoom lens joins Canon’s other offerings in the Cine arena. While some might complain about a $31,000 lens ramping from T2.9-T3.9, those familiar with Cine lenses will be well aware of the added weight and even cost that a constant aperture lens would add. Everything is a series of compromises, I suppose; everything except lens quality. The lens exhibits sharpness and contrast and I find it somewhat neutral in its rendition. While cinematographers might choose lenses on the basis of warmth or creaminess or sharpness or a host of other criteria, this lens I feel exhibits no particular bias and thus is well suited for creating whatever look is desired in post. Canon, after all, knows how to make lenses and certainly ENG lenses. So the servo mechanism is everything shooters loved about Canon’s ENG zoom. Of course, fully manual zoom, focus and iris are also available. Cine lens users will be thrilled with the lens’ 300-degree focus rotation. Shooters moving from even the HD to 4K world will quickly learn how critical focus can be with a Cine lens and larger sensor camera.

Now, for the camera itself.

The original C300 was in strong need of 4K capabilities. The C300 Mark II adds full DCI 4K and UHD resolutions recording to Canon’s XF-AVC codes. 4K recording is I-frame 10 bit 4:2:2. A significant limitation in 4K/UHD resolutions is the 30p limit. Other cameras in this category are able to record 4K/UHD 60p internally. It also does not output 4K/UHD 60p to an external recorder.

In 2K and HD resolution, the camera can record RGB 4:4:4 at 10 or 12 bits. 12 bit recording tops out at 30p. It records HD 10 bit 4:2:2 up to 59.94 fps. In HD modes, the camera records up to 120fps. In all modes, interval recording is supported. That is somewhat of a disappointment since competing cameras in this range have been able to achieve higher frame rates in HD. I would hope that Canon could address this in subsequent firmware updates.

Recording is to dual CFast 2.0 cards. An SD slot records LongGOP 2K and 4K in PhotoJPEG codec.

CFast 2.0 cards are among the priciest of all contemporary media but have proven themselves across a number of camera platforms. I tested the camera with the Lexar Professional 3400x cards and did not drop a frame even with 2K 4:4:4 12 bit footage. Note that Lexar also produces a 3500x card which it recommends for the C300 Mark II but which has limited compatibility with other CFast camera systems. For optimal reliability I would recommend using the 3500x cards. And as a final note, Lexar will be introducing a 3600x card that is incompatible with the C300 Mark II. As always the case these days, confirm card compatibility both on Canon’s site as well as with the card manufacturer.

Shooters coming from traditional cameras, as mentioned, need to relearn control positions for EOS Cinema cameras. Despite the change in traditional placement, EOS Cinema Cameras in general have well-labeled controls which activate effortlessly. Among the strongest suit of Canon is the camera menu structure. If you’ve ever had to deal with the menus of another competing manufacturer—which will remain nameless—and then move to Canon, you will really appreciate the logical arrangement of options. And it is possible to change settings without digging deeply into multi menus under multiple categories. Canon truly gets the award for menu design.

C300 users have always remarked that even in the 8-bit MPEG-2 days, there was always a certain pleasing look to the images, particularly skin tones. One user even fantasized a certain Canon secret-sauce that made 8-bit images appear much stronger than one would expect. That is certainly the case here as well. Cinema EOS cameras don’t require a lot of fiddling to look good.

The C300 could shoot in Canon Log, a rather “mild” logarithmic format which is not as flat as other log curves. It graded easily and still produces eminently usable images.

The C300 Mark II expands the dynamic range of the camera to an advertised 15 stops with the application of Canon’s C Log 2 gamma curve and additional color space options. While various independent reviewers have questioned whether it actually does shoot a genuine 15 stops of DR, pixel peeping for our purposes here is of no consequence. The facts are in the images and the images exhibit dynamic range commensurate with the needs of C300 Mark II production.

C Log 2 is a flatter curve and gives more emphasis to the highlights. Thus ungraded images may seem noisy. One recommendation here is to shoot the camera at ISO 400 rather than the native 800 ISO of the sensor. Combining that 1 stop exposure change with the appropriate LUT controls noise. In addition, the built-in noise reduction option can greatly improve footage even when shot at higher ISO’s. Noise is always a concern with LOG footage because it is dependent upon where the curve decides to place middle gray and how many stops above and below middle gray the camera can then acquire. This makes the use of LUTs significant both in the shooting as well as grading process. Canon’s web site includes LUTs for both C Log and C Log 2, with the C Log 2 LUTs applicable to all of the color gamuts offered by the camera.

Gamut is another consideration in shooting and grading, something perhaps less familiar to those moving from that traditional ENG world. The C300 Mark II has a Cine gamut, DCI-P3, ITU Rec2020, of course Rec 709 as well as ACES support. ACES will become more significant over the years as camera manufacturer’s and the Academy collaborate on profiles. The C300 Mark II is ready for the move to ACES. In addition, there is a Wide Dynamic range profile, which is not exactly LOG but which is an excellent compromise between pure Rec 709 shooting and the additional grading required if shooting in LOG.

All of these options can be output via SDI or HDMI to external monitors and recorders. RAW recording to Canon’s RAW format is available via SDI. I recorded RAW to Convergent Design’s Odyssey 7Q+ recorder with the RAW option enabled. Other than saying that my 7Q+ is one of my prized go-to devices, RAW output transforms the C300 Mark II to a cinema level production camera adding to its versatility. It is a welcome addition to the camera.

SUMMARY

The C300 Mark II remains a prime candidate for run and gun, reality and high production value sports and interview applications. Available in EF or PL mounts, the EF version supports auto functions with Canon EF and EF-S glass, something that reality shooters just often need to use. It dual processor function autofocus quickly without hunting.

In its ENG configuration as tested, it is a very heavy rig topping out at more than 25 pounds with the Cine lens and battery plus a couple more pounds for counterweight.

The lack of 4K above 30p and limited HFR abilities put it at a competitive disadvantage to other cameras of its class and its $16,000 price tag might give second thought to buyers who can find similar and sometimes greater features in less costly cameras. Price and performance ratios are very personal decisions.

The C300 Mark II at $16,000 represents a significant advance in Canon Cinema EOS technology and the ENG package at $48,000 represents a great value in a pre-configured matched system that is capable of all levels of production from reality to scripted cinema.

Ned Soltz is an independent video shooter, editor and producer, as well as consultant and general technology guru.