Twenty iPhones and a Bluescreen: What 28 Years Later Teaches VFX Teams
The iPhone-shot zombie sequel paid for its phones in post. Which problems ProRes RAW and genlock now fix, plus a phone-as-A-cam checklist.
"28 Years Later" put iPhones in front of a studio audience and got away with it. The film reportedly cost about $60M, and most of it was shot on iPhone 15 Pro Max rigs, some carrying up to 20 phones. It worked on set. The bill arrived in post. That makes it a useful case study now that Apple's newer phones claim to fix much of what went wrong. Some of it they do fix. Some of it no phone will.
What the production actually shot
The most detailed technical account comes from befores & afters' interviews with the camera and VFX teams. Cinematographer Anthony Dod Mantle used the iPhone 15 Pro Max as the main camera, running the Blackmagic Camera app. He framed for 2.76:1 rather than the 2.39:1 originally planned. For action beats the grip department built an eight-phone handheld rig and a 20-phone array, which was flown on Technocranes for studio work. Vintage lenses were adapted to the phones, and their vignetting later had to be matched in comp. Union VFX handled the visual effects. Wikipedia's production summary gives the $60M budget. We could not open IndieWire's original reporting, so treat that figure as reported.
On Apple's own iPhone 15 Pro Max spec sheet, the phone records log video and ProRes up to 4K60, the latter only to an external drive. That is a long way from a cinema camera, and the post team found out exactly where.
Four problems, sorted by whether newer phones fix them
Here are the issues reported by the VFX and camera teams, checked against what Apple and Blackmagic now ship.
| Problem on "28 Years Later" | Fixed by iPhone 17 Pro + ProDock? |
|---|---|
| Multi-phone sync: Union VFX had to line up 20-plus angles in matchmove | Mostly. Genlock via the ProDock locks capture timing |
| 4:2:0 chroma, which made bluescreen keys painful | Yes, if you record ProRes RAW |
| Matching compression artefacts across angles in comp | Largely, with raw capture |
| Apple Log converted to ARRI LogC for editorial | Partly. Apple Log 2 changes the source, but you still need a conversion step |
| In-phone stabilisation blocking tracking; clipped highlights; focus shifts not recorded | No. These are discipline and sensor problems |
Apple says the iPhone 17 Pro and Pro Max are the first smartphones to record ProRes RAW and Apple Log 2 and to support genlock. Genlock needs Blackmagic's Camera ProDock, priced at $299.95. It adds BNC genlock and timecode, HDMI out, USB ports for external drives and a DC power input. The dock also fits 15 Pro and 16 Pro models, but Apple only advertises genlock for the 17 Pro.
Where the chroma problem came from
VFX supervisor Adam Gascoyne told befores & afters he "wouldn't put it near a bluescreen again". His team leaned on grey screens instead. The 4:2:0 subsampling they describe means colour is stored at a quarter of the luma resolution. That is the worst case for a key, because the edge you are pulling is a colour edge. One detail is worth flagging. iPhone ProRes is a 4:2:2 format, so 4:2:0 footage suggests at least some material was shot in HEVC. The articles we checked do not say which codec was used for which shots, so we could not confirm this. Either way, ProRes RAW sidesteps the issue. Debayering happens in post, where you choose the quality.
What the newer phones don't fix
- Stabilisation. The production turned off in-phone stabilisation because it stopped VFX from tracking, and relied on DJI Ronin gimbals instead. Any phone will still default to stabilisation in some apps. This is a checklist item, not a hardware fix.
- Highlight headroom. Clipped highlights were on Union's list of problems. Raw capture keeps every bit the sensor records, but it cannot add stops the small sensor never captured.
- Lens metadata. Focus shifts were not recorded, which hurts matchmove. Adapted vintage glass has no electronic contacts. Someone has to log focus by hand or with an external encoder.
- Array consistency. Twenty phones means twenty units with small variations. Genlock aligns when they capture. It does not align how each one looks.
- Data load. Apple's iPhone 17 Pro specs say ProRes at 4K120 needs external recording. Expect raw multi-phone shoots to need a drive on every phone and a wrangler who can keep up.
The "phone as A-cam" readiness checklist
Use this before you commit phones to a VFX-heavy job. If you can't tick an item, budget for the post work that replaces it.
- Codec locked: ProRes RAW on any plate that will be keyed or tracked, and never HEVC on VFX shots.
- Stabilisation off in the capture app, on every phone, checked at the start of every day.
- Genlock and timecode on multi-phone arrays, from one master clock. Without them, budget matchmove time per angle.
- One log path agreed with editorial and VFX before day one: Apple Log 2 to your working space, with one documented transform. Test it on a chart.
- Grey or neutral screens rather than blue or green when chroma is compromised. That was the production's own workaround.
- Lens and focus notes for every setup, plus a vignette and distortion grid for each adapted lens.
- Exposure for highlights. Protect the top end. Phone sensors run out of headroom long before cinema cameras do.
- Per-phone calibration: shoot a chart on every unit in an array, so comp can match them to each other.
The takeaway
"28 Years Later" proved that phones can carry a studio film. It also showed that their weaknesses become VFX hours. ProRes RAW and genlock remove the two most expensive problems, chroma and sync. Stabilisation, highlight headroom and lens metadata are still your job. Run the checklist before the shoot, or pay for it in comp.
