Restorations

Here are a couple more shots from my Friday morning session in Old Town with the Kodak No.1A Folding Special.  The images were cropped to compensate for poor framing, but I like them because they show the nice qualities which the Bausch and Lomb Rapid Rectilinear lens can deliver.  I was also happy with the tonal range produced by the combination of the expired Tri-X and processing in HC110e.

The Rapid Rectiliner lens, also known as the Aplanat, dates back to 1866.  As can be seen in this illustration from Wikipedia the design features four elements in two groups arranged symmetrically on either side of the aperture.

Here are comments on the design by Rudolf Kingslake, a Director of Optical Design at Eastman Kodak Company from his book, Lenses in Photography, 1951 (p.122-123):

The Rapid Rectilinear Lens -- By 1866 lens theory had developed sufficiently to indicate how the two components of a duplet could be corrected for spherical aberration even though they were bent into the meniscus shape necessary for a flat field, the symmetry being relied upon to eliminate coma, distortion, and lateral color.  The result was the f/8 Rapid Rectilinear...

The aperture scale on my 1A Special shows a value of "4" as the widest aperture setting, however that is because the scale is using the Universal System values in use by Kodak at the time.  In that system the mid-scale value of 16 is the same as the f/16 value in the system now in use.  The next lowest value in the Universal System is expressed as 8 to indicate twice the exposure value of the previous setting.  And, the last Universal System value on my camera is 4, but that actually corresponds to f/8 in the current system of aperture values which are expressed as a ratio of focal length to aperture diameter.