Canon EOS Rebel T4i 18-135mm IS STM Lens Kit Instruction Manual page 321

The battery becomes exhausted quickly.
Use a fully-charged battery pack (p.28)
The rechargeable battery pack performance will degrade over
repeated use. Purchase a new one.
The number of possible shots will decrease with any of the following
operations:
• Pressing the shutter button halfway for a prolonged period.
• Often activating only the AF without taking a picture.
• Using the lens' Image Stabilizer.
• Using the LCD monitor often.
• Continuing Live View shooting or movie shooting for a prolonged
period.
The camera turns off by itself.
Auto power off is in effect. If you do not want auto power off to take
effect, set [52: Auto power off] to [Disable] (p.201).
Even if [52: Auto power off] is set to [Disable], the LCD monitor will
still turn off after the camera is left idle for 30 min. (The camera's
power does not turn off.) Press the <B> button to turn on the LCD
monitor.
Shooting-Related Problems
No images can be shot or recorded.
Make sure the card is properly inserted (p.31).
Slide the card's write-protect switch to the Write/Erase position (p.31).
If the card is full, replace the card or delete unnecessary images
to make room (p.31, 264).
If you try to focus in the One-Shot AF operation while the focus
confirmation light <o> in the viewfinder blinks, a picture cannot be
taken. Press the shutter button halfway again to refocus automatically,
or focus manually (p.43, 100).
Troubleshooting Guide
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