Canon Powershot S100 User Manual page 205

Information Displayed on the Screen
* : Standard, : Held vertically
When shooting, the camera detects if it is held vertically or horizontally, and adjusts settings
accordingly for the best shot. It also detects orientation during playback, so you can hold the
camera in either orientation and it will automatically rotate images for correct viewing.
This function may not operate correctly when the camera is pointed straight up or down.
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