Nikon D2H - Manual (Page 62)

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Taking Photographs—Sensitivity (ISO Equivalency)
b2—ISO Step Value ( 183)
Depending on the option selected for Custom Setting b2, sensitivity can also be set in
increments equivalent to ½ or 1 EV.
ISO step value set to 1/2 step
ISO step value set to 1 step
If possible, the current sensitivity setting is maintained when the step value is changed.
If the current sensitivity setting is not available at the new step value, sensitivity will be
rounded up to the nearest available setting.