Lock focus and exposure
Usually the iPhone will focus and expose a shot fresh each time, since that is indeed what you usually want, but there are times, usually for creative reasons, that you want to lock the focus and exposure.
To do this, tap and hold on the screen; you’ll see a series of contracting rectangles around your finger which is your cue that the exposure and focus are now locked even if you move the camera a little or to a completely different part of the scene. Tap anywhere on the image to unlock them again.
Use a hardware shutter
You can use the physical volume buttons on the side of your iPhone to take the shot rather than the big onscreen button—handy if you’re holding the phone at an awkward angle—but this also extends to headphones (including the bundled ones) that have inline volume controls on the cable.
Pro photographers would use something like this with big fancy SLRs especially as a way of reducing camera shake; the act of pressing a real or on-screen button can shake the camera at the very instant you want it to be still, so by triggering a shot using a button which is on a cable, usually with the camera held in a tripod, you’re removing that shake completely.
You can go one better: there are remote controls that connect over Bluetooth (whisper it: selfie sticks), but if you have Bluetooth headphones with volume controls already, they should work too as a completely wireless shutter trigger.
Using your Watch as a viewfinder and trigger
If you have an Apple Watch, remember that you can use it to see what your iPhone’s camera is seeing—useful in surprising situations, such as when checking the tops of cupboards for lost items or contorting yourself down the back of the TV trying to take a shot of its serial number—and for triggering a shot.
As a remote shutter, you can either have it take a shot immediately or after a short delay—you can imagine setting up for a group shot, sauntering into the scene yourself, checking the composition on your Watch, hitting the three-second delay timer then putting your hands in your pockets and a grin on your face.
There’s a self-timer on the iPhone as well, either a two-second one—more on this below—and a 10-second one which is great for those press-the-shutter-run-back-into-shot-then-hold-a-grimace-way-past-the-point-you-think-it-should-have-triggered shots. You might be able to prop your iPhone up against something for these, but consider a tripod for more control and better results if the shot is important. (See the last section for more on tripods.)
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