Canon EOS REBEL EOS T5 1200D Instruction Manual page 204

i Continuous ShootingN
Under [53: Custom Functions (C.Fn)], if [5: High ISO speed noise
reduction] is set to [2: Strong] (p.261), the maximum burst during
continuous shooting will greatly decrease. Also, the continuous shooting
speed may be slower.
When the battery level is low, the continuous shooting speed may
become slightly slower.
In AI Servo AF operation, the continuous shooting speed may become
slightly slower depending on the subject and the lens used.
The continuous shooting speed may also decrease indoors and under
low light.
99