In my last blog post I recorded some initial impressions of my newly-CLA’d Compound shutter / Dogmar 10-3/4″ lens combination, mounted on a Chamonix 45n-1 field camera. Unfortunately, between the weather and life’s less pleasant preoccupations, I have not shot further with this kit since my last posting of images. (I really dislike standing in the rain to shoot.) In rereading that post, I realize a picture is worth at least a few dozen words—especially for those readers who are not familiar with view/field cameras. So, forthwith, a primer on field-camera anatomy, abridged version.
Above, a frontal view of the lens/shutter on the camera. Notice the large the shutter housing, the black metal donut surrounding the lens. More typically the lensboard—the flat plate that holds lens and shutter, and supports the whole in the camera’s front standard—would be quite a bit larger than the shutter/lens assembly; you’d see a lot of board behind the shutter in a front-view shot like this, rather than a lot of shutter and lens, and little board. The camera’s Linhof-compatible boards (Linhof boards are a standard, and fit many smaller view/field cameras) are around 95mm square; while the diameter of this shutter is around 105mm. Look at the shutter housing at the 3 and 9 o’clock positions, and you can see it overhangs the front standards by several mm on each side. This shutter/lens assembly was intended for use on the much larger cameras that prevailed at the time; 8×10 inch cameras were about the smallest anyone used for “serious” studio work in the early 20th century.
Incongrously, the cocking lever (about three o’clock position on the front surface of the shutter housing) and the shutter release lever (about 7 or 8 o’clock) are small and dainty. The cocking lever, especially, barely extends beyond the rim of the shutter housing, so it’s tough to get at.
Above, a side view of the shutter housing (black knurled circular band of metal with serial number). Usually, this housing would lie closely against the lensboard behind it; here, notice several millimeters of offset; otherwise, the shutter would not clear the front standard (the stuff that holds the lensboard in place), the shutter’s diameter is so large.
Above, a closeup view of the aperture scale; like LF lenses in general, it’s not particularly fast, with a maximum aperture of f/4.5; but it stops down to f/45. Such small apertures are needed to make possible sufficient depth of focus with large-format lenses, so this is typical.
It’s not well shown in this view, but just above and between the “8” and the “11” on the aperture scale there’s a brass button slider. This is the shutter’s speed-range selector; at its far-left unmarked position, the shutter is set for speeds of one second or faster, chosen on the shutter speed dial (image following next.) The shutter must be uncocked in order to select “B” or “T”, and forcing it risks damaging the shutter. Moving the selector to “B” or “T” overrides whatever speed happens to be selected on the shutter-speed dial. Set to “B”, the shutter stays open as long as the shutter release lever is pressed; on “T”, one press opens the shutter, and a second press closes it. These two settings, of course, are used for longer exposures. With the slow (relatively light-insensitive) films in use way back when, and the small apertures required for meaningful depth of focus, exposures of seconds’ to minutes’ duration were common.
Above, the shutter-speed selector dial of the Compound shutter, which is now accurate and smooth as silk since SK Grimes worked its magic. My only quibble is that the knurled ring is small and flat, and tough to rotate between speed settings. Speeds range from 1 sec to 1/75 sec, attainable when the speed-range selector pictured in the previous image is at its far-left unmarked position. The cylinder atop the shutter housing, on its side behind the speed selector dial (labeled “CP Goerz”), is a pneumatic-piston device that regulates the slower shutter speeds. It contains a plunger that, when the shutter is tripped, forces air out through a small orifice, delaying shutter closing by a measurable duration that varies depending on the chosen shutter speed. When the air has been forced out of the piston, the shutter closes, ending the exposure. This works only for the slower speeds. Clever—simple and reliable. The shutter calibrated well and its speeds checked out accurately throughout its range. Note the cable-release extension entering the shutter housing at about the 11 o’clock position.
In short, I am loving this gadget. It is a thing of functional beauty. I expect to have more images, and excruciatingly boring levels of technical babble, posted here in coming days and weeks.
Insomniacs, your cure is imminent.