Aperture (f-stop) is the size of the lens opening. The smallest f-stop lets in the most light; the light gets cut in half with each click to a larger f-stop. Aperture controls depth of field.
Depth of field determines the portion of the photo that is in focus. Higher f-stop numbers allow larger depth of field, so most of the photo is in focus. Smaller f-stops create a shallow depth of field, in which the main subject is in focus but the background is blurred.
Fill flash forces a camera to add light to a shot. It’s useful in backlit or high-noon situations, or when the camera is “fooled” by surrounding light and isn’t picking up details. It’s commonly a “one-touch” camera feature.
ISO is the film speed. In a digital world it’s a measurement of the shot’s sensitivity to light. Use lower numbers for bright light and outdoor conditions; higher numbers are for conditions with low light.
Shutter speed is how fast the lens shutter opens and closes. It dictates exposure. Use faster speeds for capturing action shots.
Bracketing — Cameras with automatic bracketing features take three photos on the same shot — one with a darker exposure, one with a middle exposure and one brighter. This feature is good insurance to make sure the shot you want is not too bright or too dark.
3 Killer Apps
Camera Plus (free, iTunes)
Anti-shake feature prevents blur. Also has cropping, filters and big-button shooting features.
Fast Camera ($1.99, iTunes)
Rapid-fire shooting as soon as you open the app, and it keeps shooting until you press the stop button.
Big Lens ($0.99, iTunes)
Changes an existing photo’s depth of field. Creates images comparable to a DSLR (digital single-lens reflex) camera.