The S (ISO Sensitivity) Button
Hold the S button and rotate the main command dial to adjust the camera’s sensitivity to light according to the amount of light available. The current setting is shown in the shooting display. Choose from settings of from ISO 100 to ISO 51200; settings about 1 and 2 EV above 51200 are also available for special situations. h mode and all q modes apart from 4 offer an additional ISO-A (auto) option.
S button
Main command dial
ISO Sensitivity
The higher the ISO sensitivity, the less light needed to make an exposure, allowing faster shutter speeds or smaller apertures, but the more likely the image is to be affected by noise (randomly-spaced bright pixels, fog, or lines). Noise is particularly likely at settings of Hi 1 and Hi 2.
Hi 1 and Hi 2
Hi 1 and Hi 2 correspond respectively to ISO sensitivities 1 and 2 EV over the highest numerical value. Hi 1 is equivalent to ISO 102400, Hi 2 to ISO 204800.
Auto ISO Sensitivity Control
In modes P, S, A, and M, auto ISO sensitivity control can be enabled or disabled by holding the S button and rotating the sub-command dial. When auto ISO sensitivity control is enabled, ISO sensitivity will automatically be adjusted if optimal exposure cannot be achieved at the value selected with the S button and main command dial. To prevent ISO sensitivity going too high, you can choose an upper limit of from ISO 200 to Hi 2 using the ISO sensitivity settings > Maximum sensitivity item in the photo shooting menu.
Sub-command dial
S button
When auto ISO sensitivity control is enabled, the shooting display will show ISO AUTO. When sensitivity is altered from the value selected by the user, the altered value is shown in the display.
Auto ISO Sensitivity Control
If the ISO sensitivity selected by the user is higher than that chosen for Maximum sensitivity when auto ISO sensitivity control is enabled, the value selected by the user will be used instead. When a flash is used, shutter speed will be restricted to values between the speed selected for Custom Setting e1 (Flash sync speed) and the speed selected for Custom Setting e2 (Flash shutter speed).