Nikon D5000 User Manual page 92

"ISO sensitivity" is the digital equivalent of film speed. The higher the ISO sensitivity,
the less light needed to make an exposure, allowing higher shutter speeds or smaller
apertures.
Place the cursor in the information display.
if shooting information is not displayed in the monitor, press the [] button.
Press the ,1t, button to place the cursor in the information display.
[] button
Information display ,I], button
2
3
Display ISO sensitivity options.
Highlight the current ISO sensitivity in the
information display and press _).
Choose an ISO sensitivity.
Highlight an option and press _). ISO sensitivity
can be set between values roughly equivalent to
ISO 200 and ISO 3200 in steps equivalent to
1/3 EV. For special situations, ISO sensitivity can
be lowered below ISO 200 by about 0.3 EV
(Lo 0.3, equivalent to ISO 160), 0.7 EV (Lo 0.7, equivalent to ISO 125), or 1.0 EV
(Lo 1, equivalent to ISO 100), or raised above ISO 3200 by about 0.3 EV (Hi 0.3,
equivalent to ISO 4000), 0.7 EV (Hi 0.7, equivalent to ISO 5000), or 1.0 EV (Hi 1,
equivalent to ISO 6400). Auto and scene modes also offer an AUTO option, which
allows the camera to set ISO sensitivity automatically in response to lighting
conditions.
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