V1.02
Thom Hogan’s Complete Guide to the Nikon D300
Page 660
one aperture/shutter speed combo, but the ambient light
in the scene
will be severely underexposed
.
At a minimum, you should use the Slow Sync option or
Custom Setting #E2 to lose the slow shutter speed restriction.
But I’d recommend that you switch to Aperture-preferred
exposure mode to also remove the aperture limitation.