Nikon SB-28 - Manual (Page 90)

90
The flash ready-light in the camera's viewfinder will blink:
F90X/N90s viewfinder display is shown.
Cameras in Groups I (except F70-Series/N70), II, III, V and VI.
—in the
t mode, when you press the shutter release button halfway, to warn that
the SB-28 has not been securely mounted on the camera or that the flash output
may have been insufficient for correct exposure.
Cameras in Groups V and VI
—in the
t mode, to indicate that the ISO rating of the film in use is higher than the
ISO set on the SB-28's LCD panel, (or lower in the case of the FA camera).
Cameras in Group VI
—in the
t mode, when the shutter speed is set to M90, M250, or B.
Cameras in Group VII
—to warn that
t flash shooting is not possible.
FM3
A
, New FM2
—when the shutter speed set is faster than the flash sync speed.
Troubleshooting
S
0
Warning indications