Nikon 5700 - Manual (Page 123)

Menu Guide—Using the SHOOTING Menu
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Setting the Time Limit for Long-Time Exposures: Maximum Bulb Duration
In manual exposure mode, setting shutter speed to
BULB lets you keep the shutter open as long as the
shutter-release button is pressed (
76). The default
Maximum Bulb Duration is 1 min. There is also a 5
min option. Note that longer exposure times increase
the amount of noise visible in the final image.