42" Artar in Compound 5 ShutterA great option for mounting large barrel lenses for ULF photography
The Compound 5 shutter is a great alternative for shutter mounting large barrel lenses for ULF photography. It has an appreciably larger aperture and cell mount than the Copal 3 or Ilex 5 alternatives - so it can avoid vignetting. The Compound shutter was developed in Germany in 1905 and stayed in production until the 1970s. It was prized for its reliability and unlike modern shutters uses a pneumatic cylinder to regular the exposure time. Care must be taken when undertaking a CLA of a Compound shutter since it has delicate workings which do not take to the typical cleaning approaches used with clockwork designs. SK Grimes has a list of lenses and suggested shutters for mounting them on which is a good place to start when considering barrel mounting. Strangely this list doesn't mention the Compound 5 which is certainly a better option for a 42" Artar for example.
|Shutter||Aperture||Lens Cell Mount||Shutter to Board Mount||Max Speed|
|Copal 3||45mm||58mm||M 60mm x .75||1/125 second|
|Alphax 5||58mm||73.8mm||3.117 inches - 30 t.p.i.||1/50 second|
|Ilex 5||63mm||75mm||3.225 inches - 30 t.p.i.||1/50 second|
|Compound 5||64.5mm||82.8mm||M 90mm x1||1/50 second|
|Sinar Copal||76.2 mm (3 inches)||Mount rear of barrel to Sinar Board||Part of system||1/60 second|
|Packard||88.9mm (3.5 inches) up to 203.2mm (8 inches) custom||Custom front or rear of lens||Custom||1/25 second|
How to use the Compound Shutter
The Compound 5 shutter is similar but different to the modern Copal shutter. There is a Wheel (1) for setting the exposure time which goes from 1 second to 1/50 second. There is a Mode Setting (2) to switch between "T", "B" and "M" or manual (using the exposure time wheel). The is a Shutter Cock (3) for cocking the shutter - but this is only to be used in the "M" setting. Using the shutter cock when in "T" or "B" modes may damage the shutter. There is an Aperture Setting (4) ring for setting the f-stop. There is a manual Shutter Trigger (5) and a Cable Release opening (6) for taking the exposure. Apparently pneumatic shutters are more accurate if you pause briefly between cocking the shutter and taking the exposure to allow the cylinder pressure to equalize with the outside pressure. Note: The image below is of the Compound 4 shutter which is identical in all respects besides its size and fastest exposure time.
Compound Shutter Layout(1) Time, (2) Mode Setting, (3) Shutter Cock, (4) Aperture Setting, (5) Manual Trigger, and (6) Cable Release