Canon EOS 90D Advanced User's Manual page 118

Setting the Exposure Before Shooting (Manual Exposure)
Exposure Compensation with ISO Auto
If the ISO speed is set to [A] (AUTO) for manual exposure shooting, you
can set exposure compensation ( = 160) as follows:
[ z : Expo.comp./AEB]

[ : Expo comp (hold btn, turn

Controls]
Quick Control screen

If ISO Auto is set, the ISO speed setting will change to obtain the standard
o
exposure with the set shutter speed and aperture. Therefore, you may
not obtain the desired exposure eff ect. In this case, set the exposure
compensation.
With the camera set to the < a > mode + ISO Auto + < q > (Evaluative
o
metering) and [ 8 C.Fn I-8: AE lock meter. mode after focus] set to the
default setting ( = 558), holding down the shutter button halfway will lock the
ISO speed after focus is achieved with One-Shot AF.
To compare the current exposure to the exposure when you pressed the < A >
o
button initially with an automatically set ISO speed, press the < A > button,
recompose the shot, and check the exposure level indicator.
With ISO Auto set and [ 8 C.Fn I-1: Exposure level increments] set to
o
[1/2-stop], any 1/2-stop exposure compensation will be implemented with the
ISO speed (1/3 stop) and shutter speed. However, the shutter speed displayed
will not change.
118
)] in [ 8 C.Fn III-3: Custom