From Smartphone to Focus Station
iPhone focus control apps are specialized tools that repurpose standard iOS features such as LiDAR sensors, Bluetooth connectivity, and lens data management to integrate with professional wireless focus systems for cinema cameras, giving filmmakers a low‑cost way to monitor, label, and influence focus, iris, and zoom settings without buying extra proprietary hardware. RingThing is an iPhone app that lets you create custom focus, iris, or zoom scale labels for ARRI Hi-5, WCU-4, and Tilta Nucleus-M II hand units, while LidarAC is a third-party iOS app that integrates with Tilta’s Nucleus Nano II, Nucleus-M, and Nucleus-M II systems, allowing you to turn your iPhone into a LiDAR rangefinder to assist with focus pulling. Together, they signal a shift: the phone in your pocket is starting to look like the missing piece of a professional focus motor control stack.
RingThing: Cleaning Up the Messy Art of Focus Rings
Anyone who has spent a prep day scribbling on plastic focus disks knows how much time and accuracy gets lost in the process. For focus pullers and camera assistants, manually marking focus rings can be one of the most time-consuming parts of camera prep, especially when working with large sets of prime lenses, and the RingThing app aims at streamlining this process. Instead of manually marking focus disks, the app generates precise, printable labels that can be applied directly to ARRI and Tilta focus rings, delivering a visually superior and more consistent result in a fraction of the time. Default ARRI Hi-5 LDA ring files are already built into the app, and it acts as an on-device library for Lens Data Archive files, letting users sort by manufacturer, lens type, and serial, add notes, and share via QR codes.
The real value here is not cosmetic; it is about turning a manual, error-prone task into a repeatable workflow. RingThing uses lens calibration data in each LDA file to automatically generate focus, iris, or zoom labels tailored to ARRI Hi-5, WCU-4, or Tilta Nucleus-M II hand units. Focus pullers can customize colors, accents, and patterns for legibility or camera IDs, then output to a cutting machine, with the creators recommending glossy white vinyl followed by matte lamination for better readability. Basic functionality is free, but a Pro version is needed to import .rng files from the ARRI ECS Sync App or convert ARRI LDA files for Tilta Nucleus-M II compatibility, and the Pro version costs €22,99. Support for cmotion, Preston, and Teradek systems is in the works, and even an Android version is explicitly tied to the app’s success so far.
LidarAC: Pocket LiDAR as a Cinema Rangefinder
Focus aids have been moving toward LiDAR for a reason: pulling purely from a monitor and marks is hard, especially when you cannot justify high-end systems. If you’ve ever tried pulling focus using only a monitor and focus marks on your hand unit, you know how challenging the task can be, which is why LiDAR-based solutions such as the DJI Focus Pro have gained popularity, particularly among users who cannot justify the cost of higher-end systems like the Focusbug or ARRI UDM-1. LidarAC’s bet is simple: most people on set already carry a LiDAR sensor in their pocket – the one built into their iPhone – so why not use that to build a focus assist tool compatible with Tilta hand units.
The system requires two iPhones: one mounted on the camera and acting as a LiDAR sensor, while the second serves as a monitoring interface at the focus station. A LiDAR-equipped iPhone 12 Pro or newer on the camera sends real-time distance data to the second phone, which is paired via Bluetooth to a Tilta Nucleus Nano II, Nucleus-M, or Nucleus-M II hand unit. This effectively turns the setup into a low-budget rangefinder, with the primary limitation being the operating range of the iPhone’s built-in LiDAR sensor. On the receiving device, focus pullers see Nucleus distance readings alongside live LiDAR measurements, an interactive focus scale, a point-cloud display, and can map motors to focus, iris, or zoom, set marks, enable haptics, monitor the TX camera feed, and manage custom lens and camera profiles with Circle of Confusion, Depth of Field, and sensor offset calculations. LidarAC is now available as a free download from Apple’s App Store.
Why These Apps Matter for Wireless Focus Workflows
The most important thing about RingThing and LidarAC is not any single feature; it is the way they erode the idea that wireless focus system cinema tools must live in expensive, single-purpose hardware. RingThing is an iPhone app that lets you create custom focus, iris, or zoom scale labels for ARRI Hi-5, WCU-4, and Tilta Nucleus-M II hand units, while LidarAC integrates with Tilta’s Nucleus Nano II, Nucleus-M, and Nucleus-M II systems, allowing you to turn your iPhone into a LiDAR rangefinder to assist with focus pulling. Both apps reduce dependency on dedicated hardware controllers by repurposing existing smartphone technology. In practical terms, that means fewer bespoke gadgets, more software-defined tools, and more creative control handed back to crews who already own the phones that power these systems.
There are caveats. Printing and cutting labels still needs a Cricut-style device, and the LiDAR rangefinder filmmaking approach is limited by the iPhone sensor’s distance range and the need for two phones. Yet the direction of travel is clear: professional focus motor control is starting to look less like a box you buy and more like an ecosystem you configure. As RingThing expands to cmotion, Preston, and Teradek and potentially Android, and as LidarAC matures its modes like Subject, Spot, Nearest, Track 3D, and Track 2D, the line between dedicated focus hardware and “phone app” will keep blurring. Crews who adapt early stand to gain faster prep, smarter assistance, and more flexible rigs without waiting on the next expensive controller to ship.
