Compound Air timed Shutters

S.K. GRIMES
Compound Shutters for Large Format Photographers

A high quality older model shutter: the German made "COMPOUND"

These Compound shutters were made in great numbers and in many different sizes. The main features of their design are the air piston/cylinder at the top of the speed dial. and what turns out to be a quirk of operation by which the shutter is not cocked when operated on "B" or "T" setting, but operated by only the action of the release lever (or cable release).

On this page watch how one of these is disassembled and take a look at the mechanism. (The picture shows a typical problem of a deranged iris.)

Click on the small pictures to open a new window with a large version of the picture

Removing the speed dial, cocking lever and front cover plate reveals the very straightforward mechanism. An odd feature of these is that they operate without cocking the mechanism on "T" (Z) and "B" (B) settings selected by the three position lever at the center of the iris scale.

Removing the screws at the back of the shutter allows the mechanism to be separated from the body shell which holds the iris and iris control.

These show further disassembly: The Air retard piston/cylinder, the iris leaves (note, they're not symmetrical) and the iris control mechanism showing the axle pins dislodged from their slots.

At this stage of disassembly the parts can be inspected and cleaned using a petroleum solvent and/or detergent and water. The paper iris blades must be treated carefully. They are then dried and are ready to be lubricated sparingly (where appropriate) and reassembled.

Re-assembling the iris is a tricky business of stacking the blades around and tucking them under to their blind holes. On this one they are made of an easily damaged paper material. The travel of the air-piston is limited by the M cam under the speed dial whose position relates to the shutter speed.

The mechanism can be fully assembled and trial operated for inspection and adjustment without the iris scale cover.

Click here to hear the sound of the repaired mechanism in good order

These well made shutters suffer a poor reputation for two reasons that have nothing to do with their excellent design:

First, their odd operating ergonomics require that the cocking lever not be used when the shutter is set to the "B" or "T" functions. Forcing the cocking lever (and thereby damaging the mechanism) happens frequently when these are up for inspection at buy/sell shows or in the hands of uninstructed assistants or other users.

Secondly, they respond very poorly to the "dip in solvent and blast with compressed air" method of amateur repair. The paper product iris on this example would surely be damaged beyond repair by such treatment. They are regarded as "fussy" and, once tampered with sufficiently are, indeed, often impossible to repair.

I hope that anyone observing this page would allow for the possibility that these shutters, properly used are an excellent product.

(We also refurbish all these shutters. Contact me via phone or E-mail -- The E-Mail link at the bottom of this page will summon your own blank E-mail automatically addressed to me for your convenience.)

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