Canon EOS M Basic Instruction Manual page 417

High-speed sync cannot be set in the <f> mode.
Under [A1: External Speedlite control], set [Flash sync. speed in
Av mode] to [Auto] (p.221).
During shooting, the white <s> icon or red <E> icon is displayed.
This icon indicates that the camera's internal temperature is too high.
The white <s> icon indicates degraded still photo quality. The red
<E> icon indicates that the power will soon turn off automatically
(p.128, 201).
Movie shooting stops by itself.
If the card's writing speed is slow, movie shooting may stop
automatically. Use an SD Speed Class 6 "
find out the card's read/write speed, see the card manufacturer's Web
site, etc.
If the movie shooting time reaches 29 min. 59 sec., the movie shooting
will stop automatically.
The ISO speed cannot be set for movie shooting.
If movie autoexposure is set, the ISO speed is set automatically. You
can set the ISO speed only if movie manual exposure is set (p.181).
The exposure changes during movie shooting.
If you change the shutter speed or aperture during movie shooting, the
changes in the exposure may be recorded.
Zooming the lens during movie shooting can cause changes in the
exposure regardless of whether the lens' maximum aperture changes
or not. Changes in the exposure may be recorded as a result (except
with the EF-S18-135mm f/3.5-5.6 IS STM or EF-M18-55mm f/3.5-5.6
IS STM).
Troubleshooting Guide
" or faster card. To
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