Make a video. Choose Video, then tap the Record button, or press either volume button, to start and stop recording. Video records at 30 fps (frames per second). On iPhone SE, iPhone 6, iPhone 6 Plus, and later, you can switch it to 60 fps in Settings > Photos & Camera > Record video. On iPhone 6s, iPhone 6s Plus, and iPhone SE, you can also switch to 4K video at 30 fps in Settings > Photos & Camera > Record video.
Snap a still while recording: (iPhone 5 and later) Tap the white Shutter button.
Take it slow: (iPhone 5s and later) Choose Slo-Mo to shoot slow motion video. You can set which section to play back in slow motion when you edit the video. On iPhone SE, iPhone 6, iPhone 6 Plus, and later, you can choose between 120 fps and 240 fps. Go to Settings > Photos & Camera > Record Slo-mo.
Set the slow-motion section of a video. Tap the thumbnail, then tap Edit. Use the vertical bars beneath the frame viewer to set the section you want to play back in slow motion.
Zoom in or out for video. (iSight camera) Pinch the image on the screen. For iPhone 5 and later, zoom works in video mode as well as photo mode.