Model Index

                                                                                                     Shutter open, mirror raised and diaphragm closed. ▲

Mechanisms featured in model:

• Cloth curtain focal plane shutter.  Speeds approx. 1/8th - 60th second and "B", adjusted by knob on top plate.

• Instant-return mirror.  The "mirror" lifts and swings from a 45 degree angle in the focal plane, behind the lens, to a horizontal position against the underside of the "focusing screen".

• Automatic diaphragm.  During firing sequence, the blades (curved strips) closed to form an aperture, the size of which was set by a ring at the rear of the lens barrel.  A "depth of field preview" button (bottom left of lens mount) closed the diaphragm manually.

• Helical focussing.  A ring on the front of the lens barrel moved the diaphragm assembly fore and aft.

• Film transport.  The top plate lever turned the film takeup and winding spools, geared proportionately, re-cocked the shutter and re-tensioned the springs powering the mirror-lift and diaphragm.  An interlock locked the shutter release until the film transport sequence was completed, and another locked the wind-on lever until the shutter (once cocked) was released.

1. Ready (shutter cocked, mirror down, diaphragm open)

2. Release actuated (mirror rises, diaphragm stops down)

3. Shutter opened (first curtain released)

4. Shutter closed (second curtain released)

5. Mirror drops, diaphragm reopens, wind-on lever unlocked

6. Film advance

Builder's comment:  All the mechanisms worked in isolation, but together (complex interactions dependent on fine adjustment) in practice they would never have done.  But conceptually, all was present and correct.