Nikon 25446B D90 User's Manual - Page 186

ISO Sensitivity Settings Adjust ISO sensitivity (pg. 74). This option is available in all modes. ❚❚ ISO Sensitivity Auto Control (P, S, and A Modes Only) If Off (the default setting) is chosen for ISO sensitivity auto control, ISO sensitivity will remain fixed at the value selected by the user (see page 74). When 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 (choose lower values to prevent noise; the minimum value for auto ISO sensitivity is automatically set to ISO 200). In exposure modes P and A, sensitivity will only be adjusted if underexposure would result at the shutter speed selected for Minimum shutter speed. Slower shutter speeds will be used only if optimum exposure can not be achieved at the ISO sensitivity value selected for Maximum sensitivity. When On is selected, the control panel and viewfinder show ISO-AUTO. These indictors blink when sensitivity is altered from the value selected by the user. i A Auto ISO Sensitivity Control Noise is more likely at higher sensitivities. Use the High ISO NR option in the shooting menu to reduce noise (see page 168). Foreground subjects may be underexposed in photos taken with the flash at slow shutter speeds, in daylight, or against a bright background. Choose a flash mode other than slow sync or select exposure mode A or M and choose a larger aperture. Note that when the flash is used, the camera uses the shutter speed selected for Custom Setting e1 (Flash shutter speed, pg. 185) in place of the value selected for Minimum shutter speed. Active D-Lighting This option can be used to prevent loss of detail in highlights and shadows (pg. 119). The default setting is Auto. This option is available in P, S, A, and M modes only. 166