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iPhone 18 Pro can record 4K video at 120 fps in Dolby Vision, and it can record 4K120 ProRes only when connected to compatible external storage. For ProRes, Apple requires an exFAT-formatted drive, a USB 3 cable rated for at least 10 Gbit/s, and a drive write speed of at least 440 MB/s. That 440 MB/s figure is a drive requirement—not the video’s bitrate—so Apple’s published guidance does not support a reliable GB-per-minute estimate.
What 4K120 modes does iPhone 18 Pro support?
Apple lists 4K Dolby Vision recording at up to 120 fps on the iPhone 18 Pro Fusion Main camera. It also lists ProRes recording up to 4K at 120 fps, with external recording. Apple’s camera guide confirms that iPhone 18 Pro models can record 4K120 ProRes when connected to compatible external storage. Apple’s iPhone 18 Pro tech specs and camera user guide distinguish the two workflows.
These labels describe different things: Dolby Vision is an HDR video format, while ProRes is a video codec often chosen for editing workflows. They are not two interchangeable quality settings. The practical difference for storage planning is that Apple expressly requires external recording for 4K120 ProRes; its specs list 4K120 Dolby Vision separately.
How much storage does 4K120 ProRes use?
Apple says ProRes files can be “up to 30 times larger than HEVC files.” That is an upper-bound comparison, not a guaranteed multiplier for every clip, scene, or setting. It signals that ProRes can consume substantially more storage, but it does not tell you how many gigabytes a particular 4K120 recording will use.
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Apple’s published material does not give an exact iPhone 18 Pro 4K120 ProRes bitrate or a dependable GB-per-minute figure. Capacity alone therefore cannot be converted into a trustworthy recording-time estimate using these specifications. Avoid treating a drive’s 440 MB/s requirement as a file-size rate: it describes how quickly the drive must accept data, not how much video the phone creates per second.
External storage requirements for 4K120 ProRes
Apple’s requirements for external 4K120 ProRes recording are specific:
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- Drive format: exFAT.
- Cable: USB 3, rated for at least 10 Gbit/s.
- Drive write speed: at least 440 MB/s.
- Before each session: reformat the external storage device, as Apple directs.
Apple gives the write-speed threshold in its About Apple ProRes on iPhone support article. It is a minimum for the external drive used with 4K120 ProRes, not a claim about the clip’s bitrate. When choosing storage, verify sustained write performance rather than relying only on an advertised peak speed; leave some performance headroom instead of selecting a device that merely appears to meet the threshold on paper.
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- Choose the intended mode. Use 4K120 Dolby Vision if that is the desired capture workflow. For ProRes, plan on external recording; Apple’s 4K120 ProRes specification expressly requires it.
- Check the drive. Confirm that it supports exFAT and write speeds of at least 440 MB/s for this workflow.
- Check the cable. Use a USB 3 cable rated for at least 10 Gbit/s.
- Reformat for the session. Apple instructs users to reformat the external device before each 4K120 ProRes recording session. Ensure any files you need from the drive are backed up before reformatting.
- Plan recording time conservatively. Do not promise a fixed duration based only on the drive’s capacity; the cited Apple specifications do not publish a mode-specific per-minute file size.
Why Apple support pages can appear to disagree
Apple’s current iPhone 18 Pro specifications and camera guide explicitly document 4K120 ProRes with external recording. Apple’s general ProRes support article also contains an older resolution-and-frame-rate table whose model list omits iPhone 18 Pro and stops at earlier models. For this specific model, the model-specific current tech specs and camera guide are the direct references; the older general table should not be read as proof that iPhone 18 Pro lacks the feature.
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What the storage figures do—and do not—tell you
- Up to 30 times larger: Apple’s relative ProRes-versus-HEVC comparison; not an exact prediction for an individual clip.
- 440 MB/s minimum: Apple’s external-drive write-speed threshold for 4K120 ProRes; not the video bitrate.
- No reliable GB-per-minute estimate: Apple’s cited guidance does not publish a precise iPhone 18 Pro 4K120 ProRes recording rate.
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