GW690II 35mm Viewfinder Mask — Sliding Crop Lines

A snap-fit viewfinder mask for the Fuji GW690II that adds 35mm framing
lines inside the bright frame, with two sliding shutters letting you
switch between standard 35mm exposure (sprockets hidden) and Texpan-style
panoramic exposure (sprockets visible) without removing the mask.

Designed for shooting 35mm film loaded in the GW690II's 6×9 chamber —
a popular mod for ultra-wide panoramic photography on 35mm film. The
mask press-fits into the eyepiece opening (no glue, no screws) and the
two shutters slide vertically by 1.18mm each to reveal or hide the
sprocket-hole area.
 

== What's in the box ==
- Frame body (press-fits into eyepiece, 27.75 × 20.21 mm opening)
- Top shutter (sliding)
- Bottom shutter (sliding)
 

== Frame line dimensions ==
The mask projects two crop guides inside the GW690II's bright frame:
- Shutters OUT (panoramic): 18 × 7.5 mm window — full 35mm exposure
 with sprocket holes visible (Texpan-style)
- Shutters IN (standard):    18 × 5.14 mm window — 24mm exposed area,
 no sprockets visible
Math: pas exposed × (18/84) = window height in viewfinder.
 

== Assembly ==
1. Push the frame body into the eyepiece opening on the back of the
  camera. It press-fits — apply firm thumb pressure until the lip
  bottoms against the eyepiece bezel.
2. Insert the shutters from the eye side, tabs first, into the four
  slots in the frame's lip face.
3. Slide each shutter down (top) or up (bottom) to switch between
  panoramic and standard 35mm framing.

No glue, no screws, no tools needed.
 

== Shooting workflow ==
This mask is for 35mm film loaded in a GW690II. You'll need a separate
35mm film adapter for the camera body (3D-printable adapters and DIY
mods are widely documented elsewhere). The mask only handles framing.

Use the panoramic position when you want the sprocket-hole "Texpan" look,
or the standard position when you want clean 35mm exposure with no
visible sprockets.
 

== Notes ==
- The mask sits roughly 1–2 cm from your eye, so the printed frame lines
 will appear slightly out of focus through the viewfinder. This is
 unavoidable — only the bright frame itself (rangefinder-projected) sits
 on the optical infinity plane. The mask still gives you a clear
 peripheral indication of where the 35mm crop ends.
- If the press-fit is too loose for your specific GW690II copy, scale
 the model up by 1% in your slicer and reprint the frame.
- Bright-frame brightness varies by camera condition. On a well-cared-for
 GW690II, the frame lines will read clearly even with the mask installed.
 

== Compatibility ==
- Fuji GW690II (tested)
- Likely compatible with GW690III (same eyepiece geometry — please
 confirm and report back if you have one)
- NOT compatible with GW670 / GW690 / GSW690 (different eyepiece sizes)
- NOT compatible with GSW690II / GSW690III (different eyepiece bezel)
 

Designed and tested by an analog photographer. If you find an issue or
want a different crop ratio, let me know in the
comments.