Solution
Set the ISO speed (image sensor's sensitivity to light) to suit the ambient light level.
In the Basic Zone modes, the ISO speed is set automatically.
ISO Speed Guide
| ISO Speed | Shooting Situation (No flash) | Flash Range |
| 100-200 | Sunny outdoors | The higher the ISO speed, the farther the flash range will be. |
| 400-800 | Overcast skies, evening |
| 1600-6400, H | Dark indoors or night |
CAUTION
- If [C.Fn II -6: Highlight tone priority] is set to [1: Enable], the settable ISO speed range will be ISO 200 - 3200.
- Using a high ISO speed or shooting in high-temperature conditions may result in more grainy images. Long exposures can also cause irregular colors in the image.
- When you shoot at high ISO speeds, noise (horizontal banding, light dots, etc.) may appear.
REFERENCE
If [C.Fn I -2: ISO expansion] is set to [1: On], ISO 6400 and "H" (ISO 12800) can also be set.
1. Set the power switch to <ON>.
2. Press the <ISO> button.
3. Turn the <Main Dial> dial or press the <Cross keys> to select the ISO speed.
NOTE
- You can also set the ISO speed in the viewfinder while turning the <Main Dial>.
- With "AUTO" selected, the ISO speed will be set automatically.
About "AUTO" for Automatic 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 Mode | ISO Speed Setting |
 | Automatically set within ISO 100 - 1600 |
 | Fixed at ISO 100 |
 | Fixed at ISO 400 |
| With flash | Fixed at ISO 400* |
* If fill flash results in overexposure, ISO 100 or a higher ISO will be set.
* If an external Speedlite is used for bounce flash, ISO 400 - 1600 will be set automatically.
NOTE
When "AUTO" is set, the ISO speed will be displayed in whole-stop increments of 100, 200, 400, 800, or 1600. However, the actual ISO speed may be set more precisely. Therefore, in the image's shooting information, you may find an ISO speed like 125 or 640 displayed as the ISO speed.
