From Phone to Focus Station: The New Role of the iPhone
Using third-party iOS apps like LidarAC and RingThing, cinematographers can now repurpose the iPhone as a professional focus control interface that talks directly to industry-standard wireless lens control systems, turning a common mobile device into a practical cinema focus puller tool that combines LiDAR ranging, custom scale labeling, and live feedback for modern productions.
The key takeaway is blunt: the iPhone is no longer just a behind‑the‑scenes messaging device or emergency camera, it is becoming part of the lens control chain. A LiDAR rangefinder app such as LidarAC integrates with Tilta’s Nucleus Nano II, Nucleus‑M, and Nucleus‑M II systems, allowing an iPhone to serve as a distance‑reading brain for pulling focus. Meanwhile, RingThing turns the same phone into a design and data hub for focus, iris, and zoom scale labels on ARRI Hi‑5, WCU‑4, and Tilta Nucleus‑M II hand units. Together, they chip away at the old assumption that you need dedicated, expensive hardware for every step of focus control.
RingThing: Killing the Sharpie Tradition for Cinema Focus Pullers
For focus pullers and camera assistants, marking focus rings by hand has long been a necessary nuisance: slow, error‑prone, and ugly on a complex show. RingThing attacks that pain point with an unapologetically digital workflow. It stores LDA (Lens Data Archive) files on your iPhone, including default ARRI Hi‑5 ring data, and lets you import custom calibration files from ARRI and Tilta hand units. From there, it auto‑generates precise, printable focus, iris, or zoom labels that fit ARRI Hi‑5, WCU‑4, and Tilta Nucleus‑M II rings.
Instead of squinting at hand‑drawn lines, you get clean, highly readable scales in designs you control—colors, accents, background patterns, even camera IDs or branding. The labels are printed on glossy white vinyl, matte‑laminated to cut glare, then applied with 3D‑printable jigs for accurate alignment. Basic app functionality is free, but the Pro tier, which unlocks importing .rng files from the ARRI ECS Sync App and converting ARRI LDA files for Tilta Nucleus‑M II, costs €22,99. That price is minor compared with the labor it saves on large sets of primes, and it signals a clear shift: focus prep is becoming a software task, not a craft project.
LidarAC: A LiDAR Rangefinder App That Talks to Tilta Nucleus
If RingThing fixes the way we see focus scales, LidarAC targets how we hit those marks under pressure. Pulling focus with only monitor images and ring marks is demanding, which is why LiDAR‑based tools like DJI Focus Pro have taken off among crews who cannot justify high‑end systems such as Focusbug or ARRI UDM‑1. LidarAC’s blunt observation is that most people on set already carry a LiDAR sensor—the one built into iPhone 12 Pro or newer—and that this should be doing distance work instead of sitting idle.
The app uses one iPhone on the camera in TX mode to send real‑time distance data, and a second iPhone in RX mode at the focus station, connected via Bluetooth to a Tilta Nucleus Nano II, Nucleus‑M, or Nucleus‑M II hand unit. This turns the combination into a low‑budget LiDAR rangefinder, limited mainly by the iPhone’s LiDAR operating range. On the RX screen, you see Nucleus distance readings in red and live LiDAR measurements in green, overlaid on a large interactive focus scale with a point‑cloud visualisation. You can map motors to focus, iris, or zoom, set marks, enable haptic feedback, view the TX camera feed, and even build lens and camera profiles for Circle of Confusion, Depth of Field, and sensor offset calculations, across modes like Subject, Spot, Nearest, Track 3D, and Track 2D.
Why These Mobile Production Tools Matter Now
What makes RingThing and LidarAC important is not that they are clever; it is that they plug straight into real‑world cinema ecosystems. RingThing already supports ARRI Hi‑5, WCU‑4, and Tilta Nucleus‑M II, with plans for cmotion, Preston, and Teradek support in the works. LidarAC connects directly with Tilta’s Nucleus Nano II, Nucleus‑M, and Nucleus‑M II systems, turning iPhones into live focus assist devices instead of isolated gadgets. This integration is the line between a novelty app and a production‑ready iPhone focus control workflow.
The timing is logical. Sets are full of iPhones, and crews are under pressure to cut costs and prep time. Using the iPhone’s LiDAR sensor and on‑device storage to replace separate rangefinders and labeling hardware is more than a convenience; it is a reallocation of budget toward what appears on screen rather than what sits on the focus cart. Both apps are available as iOS downloads now—LidarAC as a free LiDAR rangefinder app and RingThing with an optional Pro tier—so the barrier to experimenting is low. The takeaway: ignoring these tools is starting to look like leaving money and speed on the table.
The Future of iPhone Focus Control in Professional Workflows
When you see an iPhone taped to a camera today, it may be recording BTS. Soon, it will more often be a core part of the focus system. Mobile production tools like RingThing and LidarAC show how readily available sensors and screens can stand in for bespoke hardware, especially for cinema focus pullers working on limited budgets or fast‑moving shows. In practical terms, that means fewer compromises between accuracy, cost, and setup complexity.
RingThing’s planned expansion to cmotion, Preston, and Teradek systems hints at a growing, cross‑vendor ecosystem where lens data lives in apps rather than on paper rings. LidarAC proves that a phone‑based LiDAR rangefinder can integrate cleanly with Tilta Nucleus hardware today. The direction of travel is clear: as more mobile apps extend the iPhone’s utility beyond photography into full professional video production workflows, assistants and focus pullers who treat their phones as serious tools—not toys—will gain a practical edge in both speed and precision.
