Canon EOS Rebel T3 18-55mm IS II Kit Instruction Manual page 150

About the Red <E> Internal Temperature Warning Icon
If the camera's internal temperature is high, a blinking red icon <E> may
appear. This blinking icon is a warning that the movie shooting will soon
be terminated automatically. If this happens, you will not be able to shoot
again until the camera's internal temperature decreases. Turn off the
power and let the camera rest for a while.
Movie shooting at a high temperature for a prolonged period will cause
the <E> icon to appear sooner. When not shooting, turn off the camera.
Movie Shooting Cautions
Recording and Image Quality
If the attached lens has an Image Stabilizer, the Image Stabilizer will
operate at all times even if you do not press the shutter button halfway.
The Image Stabilizer will thereby consume battery power and may
shorten the total movie shooting time or decrease the number of possible
shots. If you use a tripod or if the Image Stabilizer is not necessary, you
should set the IS switch to <2>.
The camera's built-in microphone will also record camera operation
noise.
If movie shooting is not possible due to insufficient remaining capacity of
the card, the movie recording size and movie shooting remaining time
(p.142) will be displayed in red.
If you use a card having a slow writing speed, a five-level
indicator might appear on the right of the screen during
movie shooting. It indicates how much data has not yet been
written to the card (remaining capacity of the internal buffer
memory). The slower the card, the faster the indicator will
climb upward. If the indicator becomes full, movie shooting
will stop automatically.
If the card has a fast writing speed, the indicator will either
not appear or the level (if displayed) will hardly go upward.
First, shoot a few test movies to see if the card can write fast enough.
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