Nikon SB 20 - Manual (Page 44)

To determine light output before selecting aperture
Use the following procedure instead of steps 4 and 5 to determine light output before selecting aperture:
_ Set the light output
' selector so the yellow
light output index indicates
the desired light output.
In the example photo, full light out­
put is selected.
2, Determine and set proper iens aperture.
' To determine correct aperture, follow both the vertical line from the
distance scale window and the dotted line from the light output window to
the point of intersection. If the lines do not intersect, move closer to sub­
ject or reset light output selector for more light output.
For example, with the film speed index at ISO 100 and zoom set ring at N,
to shoot a subject 10m away at full light output, follow both the vertical line
from figure 10 in the distance scale window and the dotted line from the
light output window to FULL. The two lines intersect at distance range indi­
cators for f/2.8—you must set your lens to f/2.8.
To take intentionally over- or underexposed pictures, open or stop-down
the lens aperture.
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