Nikon D300 - Manual (Page 201)

175
l
Rear-curtain sync
In shutter-priority auto or manual
exposure mode, flash fires just before
the shutter closes. Use to create effect of
a stream of light behind moving objects.
In programmed auto and aperture-priority auto, slow
rear-curtain sync is used to capture both subject and
background. Use of tripod is recommended to
prevent blurring caused by camera shake.
Flash mode Description