----- Original Message -----
From: "William Robb" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
(snip)
> One thing that I hadn't thought of when I bought the lens is
> it's usefulness for action stopping. With the 1/30th second
> shutter duration on the camera, it is possible to get quite a
> lot of subject movement during exposure. The lens shutter
> eliminates this problem.
(snip)
William,
Do you refer to subject movement when using flash + ambient light at the
highest X-synch of the P67, or to the 1/30 sec difference in the moment
of exposure from one frame edge to the opposite edge as the shutter
makes its traverse, regardless of how short a speed has been set?
If the first then it is time for Pentax to introduce a quicker shutter.
The current shutter is a horizontal cloth type is it not? If so then it
is probably at its design limit. Pentax needs to develop a vertical
travel metal shutter (probably titanium blinds, at this size blades
would be a major technological hurdle). When Hasselblad re-introduced
focal plane shutters to its cameras this is the route they took to get
1/125 sec X-synch from an FP shutter in a medium format camera which was
a major accomplishment at the time.
If the future of filmic photography is with medium format cameras as
another thread suggests then competition will be hot in the sector, and
my love of SMC Pentax lenses notwithstanding it would take more than
that to lure me away from the 6x7 Bronica with its interchangeable backs
and leaf shutters in ~every~ lens. In fact my 645 system is Bronica ETR
which I've had since c.1979 and was chosen because it was Bronica or
Mamiya, no Pentax on the market at that time, and the Mamiya then had FP
shutter and fixed backs and was pig-ugly as well. IMO leaf shutters are
a must in medium format SLRs because of the work that these cameras are
so often put to, portraits and industrials on location under any and all
types of lighting. It would need enormous lighting power to overcome
unbalanced ambient lighting at 1/30 sec, just one reason that high
x-synch is such a selling point in 35mm (sports or wildlife + flash
being another).
But back to subject movement, there is a reason that FP shutters are
preferable, at least for oblique aerial photography (hand held out the
window, that is). As these photos are often shot while the aircraft is
in a banking turn, there is some degree of radial subject movement
happening. With a leaf shutter lens the ~whole~ frame is being exposed
for the ~whole~ exposure which seems to exascerbate the movement. For
some reason that I cannot exactly explain (but which I've seen published
so I know its not my imagination) the travelling slit of the FP shutter
isolates each piece of film from movement that is occuring in other
parts of the frame. Don't ask me how but its true and I've seen it in
practise. During my days doing aerial photography in the early '80s I
used a Hasselblad ELM and it was always the case that 35mm shot on the
same day would be sharper edge-to-edge (but less suitable for the big
enlargements we made, unfortunately). Further, my first studio boss
photographed his aerials with a P67 and these were always spectacular,
even at 40in x 60in and bigger.
Excuse my rambling.
Regards,
Anthony Farr
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