Canon POWERSHOT S100 User Manual page 71

You can make a short movie of a day just by taking still images.
Each time you take a picture, the scene just before taking your shot will be
recorded as a movie. All the movies recorded that day will be saved as a
single file.
Choose &_.
Follow Steps 1 - 2 on p. 60 to choose 09 .
shoot.
Press the shutter button fully to shoot a still
image.
A movie of approx. 2 - 4 sec. will be
recorded just before the image is taken.
If you take a picture just after turning on the camera, selecting o 4 mode or
otherwise operating the camera, a movie may not be recorded.
You can select movies made in _ mode by date for viewing (p. 139).
71