These
shutter are constructed with a set of metal blades or leafs
which are situated in the lens construction at the focal point,
so they restrict the light but do not vignette into the projected
image. This happens because at this point the rays of light
are crossing over. It is the position where the aperture in
most lenses is positioned.
A leaf, blade or diaphragm
shutter is situated inside the lens of the camera - most compact digital
cameras now use this form of shutter - The blades open from a central
point to the outside diameter of the lens, stay open for the set duration
and then close again.
With some digital cameras
this blade shutter also doubles as the aperture and opens to the appropriate
aperture for the exposure. So if the auto exposure in the camera selects
f2.8 the shutter opens fully, if however it selects f8 it opens to this
aperture. Often these cameras only operate with 3 aperture settings
that the blades open to, and the intermediate settings are dealt with
by the length of time the blades are open.
