Things to consider…
A few advanced features to look out for
1 TIFF or raw export
You can export high-quality image formats in addition to JPEG or HEIF in iOS, but your app needs to support this. The main advantage of these much larger files is they provide far more detail for editing and printing. They apply less compression and give you the raw sensor data – with the minor caveat that without the automatic sharpening added by JPEG compression, they may initially look a little less vibrant.
2 Refocusing
If your iPhone is a dual-lens model, some apps will let you manually flip between them when shooting, or change the focus between foreground and background after a picture has been taken.
3 Light metering
Your phone’s hardware can measure light automatically – that’s how it knows to adjust exposure. But some apps have a live histogram view that will show you light levels in real time during manual control.
4 Video mode
In addition to stills, some apps provide manual control over video shooting as well – exposure, white balance and the like – which can be useful if you want to create specific looks for videos as well as photos. Apple’s video capture mode provides minimal manual control during shooting.
5 Preset modes
Manual control is great, but some apps provide quick modes like low light, time lapse or motion blur that can help you achieve special effects with just a couple of taps.