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Old April 2nd 04, 08:38 AM
Lassi Hippeläinen
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Default Focal plane vs. leaf shutters in MF SLRs

KM wrote:

I was cleaning my RZ and began wondering why each lens must incorporate its
own leaf shutter, then began wondering why we find leaf shutters only in
lenses. I understand why the shutter has to be in the lens for rangefinder
systems (proxmity of wide-angle rear elements to focal plane = insufficient
space), but why couldn't they be incorporated into SLR bodies?

That isn't the reason. The shutter leafs move at finite speed. While the
shutter is only partially open, it will shadow the corners of the image
gate, unles it is at the optical center of the lens. The diaphraghm is
about exactly there, and the shutter is as close as mechanically

In current leaf-shutter systems like the Bronica ETR and Mamiya RB/RZ, doing
so would make the lenses smaller and lighter. In focal-plane systems like
the Pentax 645N, you'd get flash synch at any speed.

I'm sure there's a perfectly good explanation I'm overlooking.What is it?

All focal plane shutters are curtains, because they can expose all parts
of the image gate the same amount of time.

-- Lassi