Learn to Light Paint on your iPhone with NightCap Camera
Artist Darren Pearson (whose work has been featured by Apple) has produced some amazing light paintings using his iPhone and Apple Watch with NightCap Camera. He’s also very kindly produced a tutorial video showing how it’s done, so you can try it yourself!
He’s also done a written tutorial, so if you’d prefer that you can find it here. Please note that focusing has changed in NightCap, and you will usually want to set it to 100 unless your subject is pretty close to the camera.