How to Focus Your iPhone Camera
If you have an iPhone 3GS or 4, you can take advantage of the Tap to Focus camera feature. By using this feature, changing the default focus area is as easy as tapping.
Normally, the camera on these models focuses on a subject in the center of the display, which you're reminded of when you momentarily see a square appear in the middle of the screen.
But if you tap elsewhere in the frame, perhaps on the face of your kid in the background, the iPhone accordingly shifts its focus there, adjusting the exposure and the phenomenon that photographers refer to as the white balance. For another moment or so, you see a new, smaller square over your child's face.
The iPhone 4 includes some other camera features that can help you get the focus just right:
Firing up the flash: The iPhone 4 is the only model with an LED (light-emitting diode) flash — or any kind of flash — so it's the only iPhone with a flash button. Tap the flash button to change the setting to On, Off, or Auto. Using the Auto setting lets the iPhone decide when it's a good idea to fire up the flash.
Using the digital zoom: Apple added a digital zoom feature to the camera as part of the iOS 4 upgrade. Tap the screen to summon the zoom slider, and then drag the slider to the right to get closer to a subject or to the left to zoom back out.
You may not always love the results you get when zooming in close. The iPhone has a digital zoom, not an optical zoom, and the quality distinction is enormous. Using the digital zoom, you can get closer to your subject by zooming in up to 5 times. A subject's imperfections — and any inadequacies on the photographer's part — may come to light.