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WCU-4: An insight into a versatile camera control system

WCU-4: An insight into a versatile camera control system

If you come from a Photography or fix lens Camcorder background, one of the most confusing and daunting things to get your head around when making the leap into Digital Cinematography can be the world of F.I.Z.

Focus, Iris and Zoom are all controlled manually at all times. This allows the D.O.P (Director of Photography) to craft an image without a computer inside the camera, trying to calculate or manipulate an image. It’s a hard thing to transition from if you shoot still images with E-TTL (Electronic Through the Lens Metering) where a Camera sets the correct exposure for you.

These functions are controlled by a Focus Puller or more commonalty known as a 1st AC (First Assistant Camera). Over the past two decades the 1st AC position has moved away from being directly connected with the camera, known as ‘pulling off the barrel’ or ‘using a manual follow focus’. The 1st Ac would often find themselves having to fit into tight spaces such as the footwell of a car to be able to control the functions of the camera. Thankfully this can now be done wirelessly, with innovations such as the Steadicam in the late 1970s and early 80s, to the more recent innovations such as gimbals and drones.

Almost as many F.I.Z (Wireless Lens Control) systems exist as Cameras. At JJ Media, we wanted to be able to offer a system that could provide a versatile solution that would be reliable and as intuitive as possible. No other system offered what the Arri WCU-4 could.

The WCU-4 is actually the name of the hand unit Wireless Compact Unit 4. Almost all Wireless Follow Focus Systems are comprised of 3 integral components. (Apart from the Alexa Mini, which we will come back to later)

1. The Hand Controller (In this case the WCU-4)
2. A Brain (At JJ we Have the Arri AMC-1 short for Active Motor Controller 1)
3. Motors (At JJ Media we have C-Force Mini Motors)


The WCU-4  (Hand Controller) connects to the AMC-1 (Brain) wirelessly and is powered by a reachable battery.

The AMC-1 Requires external power, this is where it becomes complex. Some Cameras will be able to provide external power output and some won’t. For instance, if you are planning to use this configuration with an Arri AMIRA, you will need to take SMC/EMC/AMC to RS cable from RS port on the AMIRA to the AMC-1.  For a Sony F5 or F55, you will need a different cable. All of these cables provide Power and Run / Stop. Allowing you to start and stop the camera from recording directly from the WCU-4 Handset.

But cameras such as a Canon C300MKII or Sony FS-7 do not feature a power output, so the common solution of  V-lock power plate, that features a D-Tap (power output) can be used to power both the camera and AMC-1 at the same time. A C300 Run / Stop and D-Tap cable are available.
The AMC-1 then connects to the motors (Cforce Mini Motors). Uniquely the Cforce Mini Motors daisy chain from one Motor to the next using an LBUS Cable. Other F.I.Z  systems run three interdependent cables from the brain to each motor.


Once you have your AMC-1 powered and connected to the camera and the Cforce Mini Motors mounted on 15mm or 19mm rails, it’s as simple as plugging in the LBUS cable from the AMC-1, then daisy chaining onto the second and third motor.

The Alexa Mini is the only camera that doesn’t require an AMC-1  or “Brain”.  The camera is able to communicate with the WCU-4 directly, it also features an LBUS connection to be able to power the motors.

Frequently Asked Questions

Q: I’m using Canon EF primes from my DSLR my C300MKII, will this work?

A: Yes, you can use any lens, but since Canon stills lenses do not feature ‘teeth’ for the motor to be able to turn the lens.

Q: I’ve never used a Wireless Follow Focus is it hard?

A: Before renting, why not visit us and get a hands-on overview?

Q: Why don’t I simply use Autofocus?

A: The Camera doesn’t always know what you want to be in focus. Cinematography grade lenses are always manual focus, allowing them to be built to the highest possible standards.