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 Measurement stew: Why is a square-format 120 rollfilm single- or twin-lens reflex called a 2 1/4 x 2 1/4 (inch) camera, while a rectangular-format 120 rollfilm SLR becomes a 6 x 4.5, 6 x 7, or 6 x 8 (centimeter) camera? Why are lens focal lengths measured in millimeters? And what about the nice bastardization that produces a combination I call “metricated inches,” such as a Nikon F100 SLR measuring 6.1 x 4.4 x 2.6 inches, as listed in Nikon’s latest full-line product catalog? I challenge you to find a common measuring ruler of any sort with decimal divisions of an inch. What in the world happened to fractions of an inch?
Herewith are some of the logical (or illogical) answers:
The first square-format rollfilm reflex, the Rolleiflex, arrived in the land of U.S. Customary (official name of our system of measurements in inches, feet, ounces, and pounds) in 1929. As you may know, the foot as a unit of measurement dates back to ancient English times, as does the division of the foot into 12 inches. Information on just whose English foot was initially measured and why this particular foot was chosen has been lost, but you’ll grant this is a very unscientific method of measurement. It sufficed in 1929 for the Rolleiflex to be labeled a 2 1/4 x 2 1/4reflex based on its picture size. Subsequent twin- or single-lens 2 1/4 x 2 1/4 cameras, both American-made and imported, were measured this way—and still are to this day.
In recent years, we have had a flood of imported, 120 rollfilm SLRs with smaller- or larger-than-square formats, namely 1 5/8 x 2 1/4, 2 1/4 x 2 3/4, and 2 1/4 x 3 1/8. Calling any by their fractional names, I’m sure you’ll agree, would be distinctly unhandy. Listing them by their metric sizes is, by comparison, a real pleasure: 645, 67, and 680. By the way, 2 1/4 x 2 1/4 cameras overseas are called 6x6 (or, phonetically, 6 by 6).
Liberia and the United States, at last count, are the only countries still stuck with U.S. Customary measurements. The world has passed us by in near total acceptance of the metric system—all based on a meter, measured as the distance that light travels in a fraction of a second (although I really liked the pre-1960 definition of a meter better: “The length of an international prototype platinum-iridium bar kept at the International Bureau of Weights and Standards at a temperature of melting ice and at standard atmospheric pressure of 760 millimeters of mercury”). Either definition seems more precise and stable than an ancient, unknown Englishman’s foot.
Divisions of an inch can get worse. An inch, of course, is 1/12 of a foot. Since there is no name for a smaller length than an inch, we are reduced to using fractions of an inch. Listing a measurement as “1/128 of an inch” seems more of an embarrassment than a measurement. Metric gives us measurements decimally. A millimeter is 0.001 meters; should you wish to go shorter than a millimeter, you have micrometers (0.001 millimeter), angstroms (0.0000001 millimeter), and even smaller units.
Dropping the foot
Don’t think that we in the U.S. haven’t seriously considered dropping the foot altogether and going metric. As early as 1866, an act of Congress made the use of the metric system legal but not mandatory. In 1971, the U.S. Department of Commerce recommended to Congress that “the U.S. should change to the metric system through a coordinated national program.”
And so it goes, with various U.S. agencies suggesting and urging that metric be adopted, but never ordering it done. And so it wasn’t.
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