Mamiya 645 PRO TL - Manual (Page 7)

10
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Other Features
<Mirror Lock-up>
After focusing, the mirror can be locked up before
making an exposure. This is convenient when the
camera is used at slow shutter speeds and is mounted
on a tripod for telephotography, copywork, etc.,
since even a very small amount of vibration should
be eliminated.
<Self-timer>
Shutter will be released 10 seconds after shutter
button is pressed.
<Time Exposure>
When making time exposures, the battery circuit is
automatically disconnected, to save battery power.
This is especially useful for astrophotography.