If ISO Auto is set, the ISO speed setting will change to obtain the
standard exposure with the set shutter speed and aperture. Therefore,
you may not obtain the desired exposure effect. In such a case, set the
exposure compensation.
The set exposure value will not be applied to movie shooting.
Under [z2: Auto Lighting Optimizer], if the checkmark [X] for
[Disabled in M or B modes] is removed, Auto Lighting Optimizer can be
set even in the <a> mode (p.194).
With the camera set to the <a> mode + ISO Auto + <q> (Evaluative
metering) and [8C.Fn I-8: Meter. mode, AE locked after focus] set to
the default setting (p.474), holding down the shutter button halfway will
lock the ISO speed after focus is achieved with One-Shot AF.
When ISO Auto is set, you can press the <A> button to lock the ISO
speed.
If you press the <A> button and recompose the shot, you can see the
exposure level difference on the exposure level indicator compared to
when the <A> button was pressed.
If exposure compensation (p.245) was applied in <d>, <s>, or <f>
mode, the exposure compensation amount already set will still be
maintained when the shooting mode is switched to <a> with ISO Auto
set.
With ISO Auto set and [8C.Fn I-1: Exposure level increments] set to
[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.
