Canon EF 100-400mm f/4.5-5.6L IS USM Instruction page 9

6. Tips on Using the Image Stabilizer
The image stabilizer in this lens is effective for hand-held shots under the following conditions.
●
MODE 1
ON
●
In semi-darkened areas such as indoors or outdoors
at night.
●
In locations where flash photography is prohibited,
such as art museums and theater stages.
●
In situations where your footing is uncertain.
●
In situations where fast shutter settings cannot be
used.
OFF
●
MODE 2
ON
●
When panning subjects in motion.
OFF
ENG-8