Nikon D40 - Manual (Page 49)

Reference: More on Photography (All Modes)/ISO Sensitivity 37
ISO Sensitivity
Photographs taken at slow shutter speeds are prone to blurring. If ISO sensitivity is raised
above the base setting of ISO 200 equivalent, the same exposures can be achieved at faster
shutter speeds, preventing blur. ISO sensitivity can be set to values between ISO 200 and
ISO 1600 in steps of 1EV, with a further high sensitivity setting of HI 1 available for an ISO
equivalent of roughly 3200.
(auto) and Digital Vari-Program modes also offer an Auto
setting that allows the camera to automatically raise sensitivity when lighting is poor or
lower sensitivity when lighting is bright. Rotating the mode dial from P, S, A, or M to
or a
Digital Vari-Program mode automatically restores the default ISO sensitivity of Auto.
Controls used
Sensitivity
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. Just as higher
speed films tend to be “grainy,” pictures taken at high ISO sensitivities are prone to mottling. Photos
taken at an ISO sensitivity of HI 1 are automatically processed to reduce noise, resulting in increased
recording times.
ISO Sensitivity ( 73)
ISO sensitivity can also be set using the ISO sensitivity option in the shooting menu.
10—ISO Auto ( 76)
This option can be used to enable automatic ISO sensitivity control in P , S , A , and M modes. When HI 1
is selected, automatic ISO sensitivity control is disabled .
11— /Fn Button ( 77)
ISO sensitivity can also be set using the command dial.