Canon EOS40D instruction manual About Auto ISO Speed, Shooting ISO Speed Setting Mode

i: Setting the ISO SpeedN

About “Auto” ISO Speed

If the ISO speed is set to “Auto”, the actual ISO speed to be set will be displayed when you press the shutter button halfway. As indicated below, the ISO speed will be set automatically to suit the shooting mode.

Shooting	ISO Speed Setting
Mode
	The ISO speed is set automatically within ISO 100 - 800.
1, 3, 4,	The ISO speed set automatically will vary depending on the
6, 7	shooting mode. The picture will be taken at the standard
	exposure.
5	The ISO speed is set automatically within ISO 400 - 800.
2	Fixed at ISO 100.
d	The ISO speed will be set automatically within ISO 400 - 800 so
	that a shutter speed preventing camera shake will be set.
f
	If overexposure would result at ISO 400, a lower ISO speed, as
8
	low as ISO 100, will be set.
	Normally, ISO 400 is set. Even for very bright or dark subjects,
s	the ISO speed will be set automatically within ISO 100 - 800 to
	obtain a standard exposure.
a	Fixed at ISO 400.
	Set to ISO 400 in all shooting modes including <2>.
With flash	If overexposure would result in bright light outdoors, a lower ISO
	speed, as low as ISO 100, will be set.

60