Canon PowerShot SD400 User Guide (en)

Photo Tips and Information
Tip for Using the Self-timer (p.78)
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.
How to Adjust the Exposure (p.95)
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.
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
The whole recorded image is bright, which 
makes black elements of the image appear gray. 
Shooting dark subjects or in dark places may 
cause the image to be overexposed. Adjust the 
exposure compensation towards the - end.