Nikon D3400 Reference Manual page 106

❚❚ The Electronic Rangefinder (Viewfinder Photography)
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 11 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 72, the in-
focus indicator may sometimes be displayed when the subject is
not in focus; confirm focus in the viewfinder before shooting.
A
Selecting Manual Focus with the Camera
If the lens supports M/A (autofocus with
manual override) or A/M (autofocus with
manual override/AF priority), manual focus
can also be selected by setting the camera
focus mode to MF (manual focus; 0 69).
Focus can then be adjusted manually,
regardless of the mode selected with the
lens.
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.).
82 More on Photography
46.5 mm
Focal plane mark