BOLEX H16 SBM Instruction Manual page 27

In special cases, where picture sharpness is more
important than steadiness (such as frame-by-frame
analysis of scientific phenomena, sports contests and
motion studies), it is an advantage to be able to
reduce exposure time, without changing filming speed,
as this diminishes the blur caused by a moving subject.
Increased picture sharpness is especially useful for
projection on wide screens. To safeguard against the
risk of jerkiness, due to the shutter being partially
closed, the filming speed should be increased-for
instance: to 24 f.p.s. or over when filming with
the
shutter half closed.