Canon EOS 90D Instruction Manual page 428

ISO Speed Settings for Still Photos
ISO Speed Range Used With ISO Auto
The [Minimum] and [Maximum] settings will also function as the minimum
o
and maximum speeds for ISO speed safety shift ( = 558).
216
1
Select [Auto range].
2
Set the minimum limit.
Select the minimum limit box, then press

< 0 >.
Select the ISO speed, then press < 0 >.

3
Set the maximum limit.
Select the maximum limit box, then

press < 0 >.
Select the ISO speed, then press < 0 >.

4
Select [OK].