All true, including the comments on measurement. One other thing to
remember is that a leaf shutter is a mechanical engineering problem.
Increase the spring power and/or decrease the moving mass, and you can
decrease the opening and closing time. Then the proportion of total time
open that is partial decreases and variation in integrated exposure with
aperture decreases. All the usual variables of mechanical systems come
into play, including design quality, materials and manufacturing costs,
performance vs. reliability, etc., etc.... I'm sure it's possible to
design a true 1/2000 sec. leaf shutter for 35mm size lenses using
titanium, CF, etc., but simply not cost effective in the marketplace.
The higher the forces/speeds and lighter the components, the more often
repair/adjustment is necessary. Think about that mechanism in each lens
vs. one focal plane shutter for all lenses.
Moose
Hughes wrote:
The interesting thing with leaf shutters is that because the leaf *travel time*
effectively gives
a variable aperture during exposure you need to measure the integrated light
exposure rather than
just use a simple thresholded light level start-stop timer to test the
lens/shutter correctly. In
other words, what counts is *not* the "shutter speed" but the integrated light
exposure at the
particular aperture set (the exposure value). Where the diaphragm axis and the
shutter axis are
close together this means the shutter speed might read say 1/500 at smallest aperture but
"only"
1/300 fully open.
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