The Bolex 18-5 projected 8mm film at fixed running speeds of 18 and 5 frames per second in forward motion, and 18 fps in reverse; 18 fps forward and reverse with the lamp switched off was also possible.
Slow motion projection at 5 fps was an exclusive feature to the 18-5, made possible by a variable shutter blade. At this speed, a typical three-bladed shutter would produce a noticeable flicker and increase the risk of film burn.
However, Bolex solved this problem by designing a three-bladed shutter that expanded to nine blades when the speed was set to 5 fps; flicker and risk of film burn were eliminated, although picture brightness was slightly reduced.
A removeable lid, built-in carrying handle, folding reel arms and small size made this projector easy to transport. A plastic cover and an aluminum 400ft reel were included with this model (both with Bolex logo); larger carrying cases with room for accessories could be purchased separately.
Unfortunately, the Bolex logo plate, located on the side of the projector and detachable lid, were simply glued on. As such, it's common to find 18-5 and 18-5 Auto projectors with logo plates missing or loose.
Data sheet