Canon POWERSHOT S500 User Manual page 155

Normally the camera shakes a little when you press the shutter button.
Setting the self-timer to [] delays the shutter release for 2 seconds and
allows the camera to stop shaking, thus preventing a blurred image.
Even better results can be obtained by placing the camera on a stable
surface or by using a tripod to shoot.
This camera automatically adjusts the exposure to shoot images with the
optimal brightness. However, recorded images may sometimes be brighter
or darker than the actual image depending on the shooting conditions. If
this happens, adjust the exposure compensation manually.
Underexposure
The whole recorded image is dark, which
makes white elements of the image appear
gray. Shooting bright subjects or in backlit
conditions may cause the image to be
underexposed. Adjust the exposure
compensation towards the + end.
Optimal Exposure
Overexposure
The whole recorded image is bright, which
makes blackelements of the image appear gray.
Shooting dark subjects or in dark places may
causethe image to be overexposed. Adjust the
exposure compensation towards the - end.