Nikon D3s Body Only D3S User's Manual - Page 126

The Electronic Rangefinder If the lens has a maximum aperture of f/5.6 or faster, the viewfinder focus indicator can be used to confirm whether the subject in the selected focus point is in focus (the focus point can be selected from any of the 51 focus points). After positioning the subject in the selected focus point, press the shutter-release button halfway and rotate the lens focus ring until the in-focus indicator (I) is displayed. Note that with the subjects listed on page 98, the in-focus indicator may sometimes be displayed when the subject is not in focus; confirm N focus in the viewfinder before shooting. A Focal Plane Position To determine the distance between your subject and the camera, measure from the focal plane mark (E) on the camera body. The distance between the lens mounting flange and the focal plane is 46.5 mm (1.83 in.). 100 Focal plane mark