How to slow mo iPhone video without making it look choppy

You’ve seen those cinematic shots on Instagram where a skateboarder hangs in mid-air for what feels like an eternity, or a glass of water shatters in glorious, crystal-clear detail. Then you try it. You go into your camera roll, hit edit, drag those little sliders, and—bam. Your footage looks like a laggy Zoom call from 2020. It’s jittery. It’s dark. It’s just... bad.

Understanding how to slow mo iPhone video isn't actually about the "Slow-mo" button in the camera app. Well, it is, but mostly it isn't. It’s about frame rates. If you don't have enough frames, your phone has to "fake" the movement, and that’s where the stuttering comes from. It’s physics, basically.

The big mistake everyone makes with frame rates

Frames per second (fps) is the holy grail here. Think of a flipbook. If you have five drawings to show a person jumping, it’s going to look like a stop-motion nightmare. If you have fifty, it’s smooth as butter. Most standard iPhone video is shot at 30 fps or 60 fps. If you take a 30 fps video and try to slow it down by half, you’re suddenly at 15 fps. The human eye starts noticing individual frames at anything below 24 fps. That’s why your video looks like a slideshow.

If you want to do this right, you need to plan ahead. You can't just take a regular video and expect it to look like The Matrix later. You have to toggle the settings before you even hit record. Go to Settings > Camera > Record Slo-mo. You’ll usually see two options: 120 fps and 240 fps.

Choose 240 fps if you want that super-dramatic, ultra-slow look. But there is a catch. A big one.

Lighting is your best friend (and your worst enemy)

Here is the thing nobody tells you: high frame rates eat light. When you shoot at 240 fps, your shutter is opening and closing 240 times every single second. That means it’s only open for a tiny fraction of time. If you aren't standing in direct sunlight or under massive studio lights, your slow-mo video is going to look grainy, noisy, and dark.

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Honestly, trying to shoot 240 fps indoors under standard LED bulbs is a recipe for disaster. You’ll get this weird flickering effect. That’s because your lights are actually pulsing at a frequency (usually 50Hz or 60Hz) that the camera is fast enough to catch. It’s annoying. If you see flickering, switch back to 120 fps or move closer to a window. Natural light is king for this.

How to slow mo iPhone video after you’ve already shot it

So, you’ve got the footage. Now what? When you record in the dedicated Slo-mo mode, the iPhone automatically chooses a section to slow down. It’s usually the middle bit. But maybe you wanted the beginning to be slow, or the very end.

Open the video in the Photos app and tap Edit. Look at the bottom. You’ll see a row of vertical white bars. The ones that are spaced far apart represent the slow-motion section. The ones bunched together are normal speed. You can slide the taller bars at the beginning and end of that section to change exactly when the "time warp" happens. It’s surprisingly intuitive once you stop overthinking it.

What if it wasn't shot in Slo-mo mode?

This is where things get tricky. If you recorded a standard 60 fps video and now you want it slowed down, the Photos app won't give you those magic sliders. You’ll need an app like iMovie or LumaFusion.

In iMovie:

1. Start a new project and drop your clip in.
2. Tap the clip on the timeline.
3. Hit the "speedometer" icon at the bottom.
4. Drag the slider toward the turtle.

If you shot at 60 fps, you can safely go to 50% speed (which results in 30 fps). It’ll look great. If you try to go to 25% speed, it’s going to get choppy. You’ve been warned.

The professional secret: Variable speed ramping

If you want your videos to look like they were edited by a pro, you need to learn speed ramping. This is when the video starts at normal speed, quickly zips into slow motion for the "impact" moment, and then speeds back up. Apple’s native editor does a "soft" version of this, but for real control, you might want to look at the CapCut app or VN Video Editor.

These apps allow you to set "keyframes." You can literally draw a curve. High points on the curve are fast; low points are slow. This creates a much more organic feeling than the sudden thud of the iPhone’s default slow-mo transition.

When to actually use 120 vs 240 fps

It’s tempting to just leave it on 240 fps all the time. Don't.

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240 fps records at a lower resolution (usually 1080p) compared to some of the 4K options available at lower frame rates. If you’re filming something like a person walking or a dress twirling, 120 fps is plenty. It keeps the detail sharp. Save 240 fps for high-speed action:

• Water splashing.
• Popping balloons.
• Dogs shaking off water.
• Sports highlights (like a golf swing).

A note on "Cinematic Mode"

Since the iPhone 13, we’ve had Cinematic Mode. It’s cool for blur, but it’s notoriously bad for slow motion. As of current iOS versions, you can't natively shoot "Slo-mo" within "Cinematic Mode." You have to pick your poison: do you want the blurry background, or do you want the slow motion? If you really need both, shoot in Slo-mo and use a third-party app like Focus Live to try and add depth of field in post-production, though it’s never quite as clean as the hardware doing it.

Stability matters more than you think

When you slow things down, every tiny camera shake is magnified. A one-second jitter becomes a four-second earthquake in slow motion. If you don't have a gimbal (like a DJI Osmo), try the "T-Rex" method. Hold the phone with both hands, keep your elbows tucked tight against your ribs, and move your entire upper body instead of just your arms. It sounds silly, but it works.

Also, avoid digital zoom. Just don't do it. Digital zoom ruins the resolution, and when combined with the lower light intake of high frame rates, your video will look like it was filmed on a potato. Walk closer to the subject.

Actionable steps for your next shoot

To get the best results immediately, follow this specific workflow:

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1. Check your storage. Slow-mo files are massive because they contain hundreds of images per second. Make sure you have at least a few gigabytes free.
2. Clean your lens. It sounds basic, but at high frame rates, a fingerprint smudge creates a "haze" that looks significantly worse than in standard video.
3. Lock your focus. Long-press on the screen where your subject will be until you see "AE/AF Lock." This prevents the camera from hunting for focus while the action is happening.
4. Move the sliders manually. Don't trust the iPhone's auto-placement. Go into the edit mode and fine-tune the start and end points of the slow-mo effect to catch just the peak of the action.
5. Export at the right settings. If you're moving the clip to a computer or another app, make sure you aren't downsampling it to 720p by accident. Keep that 1080p or 4K integrity.

If you’ve followed these steps and the video still looks "off," check your environment. Most "failed" slow-mo shots aren't a software issue; they’re a lighting issue. Move outside or turn on every light in the room.