rapid rectilinear lens design

Rapid Rectilinear lens design

Toronto.After the announcement of photography early in 1839, there was a flurry of competing lens designs across Europe, each design trying to better the resolution and error correction qualities of the other.

In 1866, two Germans, one an immigrant to England (Dallmeyer) and the other in Germany (Steinheil) independently came up with the idea of using two couplets centred about a diaphragm. Dallmeyer called his idea a Rapid Rectilinear lens while Steinheil called his slightly earlier design (literally days earlier) an Aplanat. Dallmeyer patented in Britain an earlier lens as a Wide-Angle Rectilinear design. It was patented a few years later in America (USPO).  It quickly became apparent to Dallmeyer that a slight change would improve his lens and so the Rapid Rectilinear design was born.

It was so popular that others used it for the rest of the century in everything from extreme wide angle  lenses like the Globe by Harrison and Harrison or the Pantoskop by Emil Busch, to portrait and telephoto lenses. Makers used a bewildering variety of trade names to try to differentiate their version as the “best” (the Globe and Pantoskop lenses went to market a few years before the 1866 date mentioned above).

In 1989, Rudolph Kingslake, in his book, A History of the Photographic Lens, nicely summarizes the Rapid Rectilinear design. The design was relegated to history in the early 1900s when Paul Rudolph of Zeiss created the Tessar which offered even better resolution and error correction.

When I was a youth, the design often showed up in projector lenses of the time where high resolution and error correction was less critical. In the late 1950s/early 1960s, Bell added a third floor extension to its Barrie central office for the Toll board and other long distance telephony and specialized equipment. We had a projector meter that was activated when plugged into a long distance circuit. The meter was used with a sound generator to measure the volume setting in the circuit. I decided one lunch hour to disassemble the projector lens. I discovered it to be a simple rapid-rectilinear design. When I reassembled it, I reversed one couplet by accident. The projected image was now fuzzy at either edge when sharp in the centre. Restoring the couplet to its original direction solved the problem.

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