open gate records the full sensor instead of a cropped aspect. on iphone 17 that's a 3840x3840 square. you perform once, then crop every platform later.
here's what that really means, and why it's the smartest source you can shoot from.
what "open gate" even means#
most camera apps hand you a pre-baked aspect ratio. you pick 9:16, the app crops the sensor to 9:16, and the cropped result is what gets written to the file. the pixels outside that crop are gone. they were captured by the sensor and then thrown away before they ever hit disk.
open gate skips the crop. it writes the sensor's full readout to the file, edge to edge. the term comes from film. an open gate exposes the entire film frame instead of masking it down to a delivery format. same idea here. capture everything the sensor sees, decide the framing later.
the iphone 17 front sensor is square#
this is the part that makes open gate special on the newest phones.
the iphone 17 family front camera has a 1:1 sensor. it's physically square. older iphones (16, 15) have a 4:3 front sensor, which is taller than it is wide. when you shoot open gate on an iphone 17, open prompter writes that whole square out at 3840 by 3840.
a square is the most useful shape you can start from. it has headroom on every side. there's room to crop a tall vertical, a wide horizontal, a classic 4:3, or leave it square. all from the one file.
why a square is the reframe-friendly source#
think about what each platform wants.
- 9:16 vertical. tiktok, reels, shorts. tall.
- 1:1 square. the feed post that doesn't care about orientation.
- 4:3 classic. the old-school upload, still around.
- 16:9 horizontal. youtube, the landscape cut.
shoot any one of those natively and you're locked into it. a 9:16 file has no extra width to make a 16:9. a 16:9 file has no extra height to make a 9:16. you cropped at capture, so you cropped your options too.
a 3840x3840 square has slack in both directions. drop it in your editor, set the crop to 9:16, export. change the crop to 1:1, export again. then 16:9. one read, every aspect ratio, no reshoot.
the numbers back this up. a 9:16 crop out of a 3840 square is 2160 wide and the full 3840 tall. a 16:9 crop is the full 3840 wide and 2160 tall. both come out of the same file at full resolution. you're not upscaling a small crop. you're framing a window inside a big square and exporting what's in it.
this is the whole pitch. reshooting the same script four times because four platforms want four shapes is a waste of your face and your afternoon. perform it once. let the editor do the reframing.
one take, every platform#
the workflow is boring in the best way.
- set open prompter's aspect ratio to open gate (Settings, Recording, Aspect ratio).
- read your script and record. the full square saves.
- open the take in your editor. crop a 9:16 for tiktok.
- duplicate, recrop to 16:9 for youtube, 1:1 for the feed.
you can even move the crop window around inside the square. if you drifted left in the take, slide the 9:16 frame left to recenter your head. that flexibility doesn't exist when the crop already happened in-camera.
how developers use it#
"open gate" isn't a setting most camera apps expose. the full-sensor readout is there in the capture APIs, but the typical app masks it to a delivery aspect before you ever see the file. you get the cropped result and the headroom is gone.
open prompter is one of the apps that hands the full readout to you instead. we built the recording pipeline on the sample-buffer path (AVAssetWriter) specifically so we control what gets written. when you pick open gate, you get the sensor's whole frame in the .mov. the reframing budget is yours, in post, where it belongs.
that's also why the file is bigger and squarer than you might expect. it's not a bug. it's every pixel the sensor saw, kept on purpose so you can crop into it later.
if you're a developer poking at iphone camera capture yourself, this is the behavior worth knowing about. the full readout is available, but you have to choose to write it instead of letting the framework hand you a cropped default. that's the choice open prompter makes for you. the headroom survives all the way to the file.
the rest of open prompter, briefly#
open gate is one of five aspect ratios. there's also 9:16, 1:1, 4:3, and 16:9 if you'd rather lock the shape at capture and skip the editing step.
all of it is front-camera recording in HEVC, with a tally-light border and a Dynamic Island timer so you know you're rolling. the camera lives inside the teleprompter as a small tile near the lens, so your eye-line stays close while you read. it never gets jammed behind your text.
and the script you're reading is just a markdown file from a folder you pick. write it on your mac, save it, the phone catches up. record the open-gate take, and if you turn on "save next to the script," the .mov lands right back in that same folder next to the .md.
try open gate on your next shoot#
if you're on an iphone 17, switch the aspect ratio to open gate before your next batch of clips. record once. then go crop a vertical, a square, and a horizontal out of the same take and see how much shooting time you got back.
open prompter is free and MIT-licensed. open gate, all five aspect ratios, the camera, the recorder, all of it.