Canon PowerShot SX400 IS Black Manual (en)

On-Screen Frames
 Still Images 
A variety of frames are displayed once the camera detects 
subjects you are aiming the camera at.
A white frame is displayed around the subject (or person’s 
face) determined by the camera to be the main subject, and 
gray frames are displayed around other detected faces. 
Frames follow moving subjects within a certain range to 
keep them in focus. However, if the camera detects subject 
movement, only the white frame will remain on the screen.
When you are pressing the shutter button halfway and the 
camera detects subject movement, a blue frame is displayed, 
and the focus and image brightness are constantly adjusted 
(Servo AF).
Try shooting in [
frames are not displayed around desired subjects, or if frames are 
displayed on the background or similar areas.