When the HDR (High Dynamic Range) is selected, then the camera takes multiple shots with different exposures for the same scene. The camera automatically combines the best and most detailed images into one. To choose this option, there is an HDR button at the top middle of the screen. If you are using iOS 5 or a higher version, you can easily spot the Option button at the top of the screen. Tap it and you will see a slider to turn on the HDR.