Nikon D3s Body Only User Manual - Page 132

Auto ISO Sensitivity Control If [Off ] (the default setting) is chosen for the [ISO sensitivity auto control] option in the shooting menu, ISO sensitivity will remain fixed at the value selected by the user (see page 104). If [On] is chosen, ISO sensitivity will automatically be adjusted if optimal exposure can not be achieved at the value selected by the user (flash level is adjusted appropriately). The maximum value for auto ISO sensitivity can be selected using the [Maximum sensitivity] option in the [ISO sensitivity auto control] menu (the minimum value for auto ISO sensitivity is automatically set to ISO 100; note that if the value selected for [Maximum sensitivity] is lower than the value currently selected for [ISO sensitivity], the S value selected for [Maximum sensitivity] will be used). In exposure modes e and g, sensitivity will only be adjusted if underexposure would result at the shutter speed selected for [Minimum shutter speed] (1/4000-1 s). Slower shutter speeds may be used if optimum exposure can not be achieved at the ISO sensitivity value selected for [Maximum sensitivity]. When [On] is selected, the viewfinder and rear control panel show ISO-AUTO. When sensitivity is altered from the value selected by the user, these indicators blink and the altered value is shown in the viewfinder. 106