Dual recording iPhone basics
When you start a dual recording, the iPhone runs two camera sensors and two video pipelines at the same time. Both streams share one clock, so the front and back views stay in sync without any editing. Apple's framework for this needs an A12 chip or newer, so dual recording works from the iPhone XS onwards.
What a dual camera recorder adds
A dual camera recorder is an app that manages both cameras for you: the previews, the layout, the recording and the saving. The good ones also deal with what makes dual recording hard in practice, which is usually that you are standing in front of the phone rather than behind it.
Lookout is a dual camera recorder for iPhone, Mac and Apple Watch. On iPhone it records the front and back cameras together; on Mac it records the built-in webcam alongside an iPhone used as a Continuity Camera; on Apple Watch it acts as a remote with a live preview of both views.
Getting stable footage
Two cameras make shake twice as noticeable. Always put the phone on something: a tripod, a clamp, a shelf. If you have to hold it, hold it with both hands close to your chest and walk slowly.
Getting even light
Dual recording's biggest giveaway is one well-lit view and one dark one. Because the cameras point in opposite directions, the light that makes the scene look good is often shining straight into the other lens. Stand side-on to a window rather than facing it or turning your back to it.
Getting clean sound
Both views share the phone's microphones. Place the phone closest to whoever is speaking most. For interviews or anything where sound matters, record audio separately and clap at the start so you can line it up in editing.
How long can you record?
There is no fixed limit in Lookout, but the phone is. Dual recording writes about twice the data of a normal video and makes the phone work harder, so long takes fill storage faster and warm the phone up. For events longer than half an hour, record in segments and give the phone a break between them.