Leaf Shutter
A shutter built into the lens from overlapping blades that open from the centre outward and close the same way.
Measured in
seconds
In depth
Because the whole frame is uncovered simultaneously, a leaf shutter synchronises with flash at every speed it offers, right up to 1/1000 s or beyond. That makes it invaluable for overpowering sunlight with flash. The trade-off is a slower top speed than a focal-plane shutter and a separate shutter mechanism inside every lens.
Examples in practice
A leaf-shutter medium-format lens lets a photographer shoot f/5.6 at 1/800 s with flash, killing bright ambient light entirely.