If you have ever tried to shoot ProRes on an iPhone, you already know the problem. You hit record, the file size climbs, and a minute later your phone is begging you to delete photos. ProRes is a beautiful codec to grade, but it eats storage at a rate that makes the internal drive feel like a joke.
The fix is simpler than most people think. You can record ProRes straight to an external SSD over the USB-C port, which means your phone storage stops being the bottleneck. In the video above I unbox the Lexar SL400 GO hub and walk through why I keep one in my bag, but the technique works with most fast SSDs. Here is how it all fits together.
Why ProRes fills your phone so fast
ProRes is a high bitrate, lightly compressed codec. That is the whole point. It keeps more image data so the footage holds up when you push color and exposure in the edit. The trade is file size. Where a normal phone video might use a few hundred megabytes a minute, ProRes can chew through several gigabytes in the same span, especially at 4K and higher frame rates.
On a phone with limited internal storage, that math runs out fast. You get a couple of minutes, maybe less, before the camera app stops you. Recording to an external drive sidesteps the problem entirely. The data writes to the SSD instead of the phone, so your capacity is whatever the drive holds.
What you need to record ProRes externally
You do not need much, but each piece matters. If any link in the chain is too slow, the recording can drop frames or refuse to start.
- An iPhone that supports ProRes recording to external storage over USB-C.
- A fast external SSD, ideally one rated comfortably above the bitrate you plan to shoot.
- A proper USB-C cable rated for data, not a cheap charge-only cable.
- Enough free space on the drive for your shoot, since ProRes adds up quickly.
The Lexar SL400 GO I cover in the video is a hub-style drive, which is handy because it stays compact and connects cleanly to the phone. Plenty of standard SSDs work too. The thing to watch is sustained write speed, not just the headline number on the box.
How to set it up step by step
Once you have the gear, the actual setup takes about a minute. The order matters a little, so here is the flow I use.
- Format the SSD so the phone can write to it. A drive formatted for a Mac or PC usually works, but confirm the phone recognizes it before you rely on it.
- Plug the SSD into the iPhone with your data cable.
- Open the Camera app and switch the video format to ProRes.
- Look for the indicator showing the external drive is connected and selected as the destination.
- Hit record and watch that it is writing to the SSD, not the phone.
I always run a short test clip before the real shoot. Record ten seconds, stop, and confirm the file landed on the drive and plays back. It takes seconds and it has saved me from discovering a bad cable at the worst possible moment.
Drive speed is the thing that bites people
This is where most failed setups go wrong. A slow drive cannot keep up with the data ProRes throws at it, and the phone will either stop recording or warn you. The number to care about is sustained write speed under load, because some drives post a fast peak and then slow down once they heat up or fill past a certain point.
So give yourself headroom. Pick a drive comfortably faster than your worst case bitrate, and do not run it completely full. A drive that is nearly packed can slow down, and that is exactly when you want it solid. Heat matters too. On a long take, a tiny passive drive can warm up and throttle, so a unit built to handle steady writes is worth the small extra cost.
The takeaway
Running out of storage mid shoot is one of those problems that feels unsolvable until you realize you were aiming at the wrong target. The fix is not deleting more files or buying a phone with a bigger drive. It is moving the recording off the phone entirely and onto an SSD that is fast enough to keep up.
Get the three pieces right – a supported phone, a fast drive with headroom, and a real data cable – and ProRes on an iPhone goes from a frustrating gimmick to something you can actually shoot with all day. Test before you trust it, leave space on the drive, and you are set.
If you want to see the exact drive I use and the rest of what is in my bag, check out my gear page, or head over to the blog for more practical workflow tips like this one.
