Date: Thu, 5 Dec 1996 10:04:00 -0500 
Date:         Thu, 5 Dec 1996 10:04:00 -0500
Reply-To:     MARTIN TAI <martin.tai@w....>
Sender:       The Subminiature Photography Mailing List
              <SUBMINI-L@LISTSERV.AOL.COM>
From:         MARTIN TAI <martin.tai@W....>
Organization: Westonia Computer Systems of Canada
Subject:      Minox shutter and Xsync
 
             Minox Shutter and Flash Sync
 
 
      Post war Minox  submini cameras use  a two-blade
IN-FRONT-OF-LENS shutter.  It is not focal plane shutter.
    In operation the Minox shutter works resembles Kodak
baby Brownie moving  hole  shutter.
    Though it has two blades, during exposure,  one blade
is stationary, only one blade is travelling at high speed
across the lens, its square openning passing the lens
thus expose the film.
 
 
 
    Heckmann's book has several diagram illustrating
the various position of the shutter openning in relation
to the lens openning.
 
     Looking from in front of the lens, the opening and closing
of the  shutter  expose the lens  in the following sequence
 
 
         1)     BEGIN: Lens fully covered
 
                      <-------  direction of  shutter travel
 
                        |----
           lens   (  )  |   |   square hole on moving blade
                        |---|
 
 
 
         2)   Lens  begin to expose
 
 
                     |----
                   ( |)  |
                     |---|
 
                      <-------  direction of  shutter travel
 
 
 
 
          3)  Lens  fully open
 
 
                     |----
                     |( )|
                     |---|
 
                      <-------  direction of  shutter travel
 
 
          4)  Lens partially closed
 
 
 
                   |----
                   |  (| )
                   |---|
 
                      <-------  direction of  shutter travel
 
          5)  Lens fully closed
 
 
 
                 |----
                 |   |(  )
                 |---|
 
                      <-------  direction of  shutter travel
 
 
 
 
    Base on its principle of operation, I reconstruct the
following  shutter timing diagram, the numbering corresponds
to the phases 1)- 5)
 
 
 
 
                 / ---------------------------------\
              /                                        \
          /                                                \
-------/-------------------------------------------------------->
  (1)          (2)             (3)                  (4)       (5)
 
                                                         time axis
 
 
 
   A mechanical retarting device  control the timing of  phase (3)
for lens fully opening, at slow shutter speed, this interval
is longer, and for high shutter speed, this phase is short
 
    The following diagram illustrates the timing from
slow shutter speed to high shtter speed
 
 
    SLOW SHUTTER  SPEED
 
 
                 / ---------------------------------\
              /                                       \
          /                                                \
-------/--------------------------------------------------------
 
 
 
 
     SHUTTER AT MEDIUM SPEED SETTING
 
 
                 / --------\
              /                \
          /                        \
-------/--------------------------------------
 
 
 
     SHUTTER AT HIGH SPEED SETTING
 
                  __
                 /  \
              /         \
          /                \
-------/------------------------
 
 
 
     In fact the timing diagram of Minox shutter is identical to
that of to COMPUR or Pronto type leave shutter
     A shutter of this type in principle is capable to flash
 sync at maximum shutter speed.
 
     To achieve highest flash sync speed, it requires to
trigger the electronic flash exactly at  point T, which is very
short.
 
 
 
                  T
                  __
                 /  \
              /        \
          /               \
-------/------------------------
 
 
 
     This requires exact timing.
 
 
 
     Obviously, Minox designer chose to adopt a more relax timing
scheme, put the x sync trigger point some where further down
 
 
 
 
    XSYNC AT  MEDIUM SPEED SETTING
 
 
 
                        |
                 / -----|--------\
              /         |          \
          /             |            \
-------/----------------|----------------------
 
                     X SYNC trigger
 
 
   In this way,  if the X sync is slightly earlier or latter due
to  normal  production variations, the flash  will still occurs
 during  a fully opened lens.
 
   In Mike's experiment with flash sync at higher speed, the flash
sync point occurs probably at phase  (4), when the lens is partially
closed.--- this explains  the  light fall off
 
 
 
 
 
                      |
                 / - \|
              /       | \
          /           |    \
-------/---------------------\-----------------
                        (4)
                     X SYNC trigger
 
 
 
Martin Tai