RADIAL DRIVE DAGUERREIAN LENS
C.C. Harrison, New York 1854-1855
Radial drive half-plate daguerreian lens by Charles C. Harrison, Serial No. 2943 circa 1854-1855.
This particular version with the large focusing knob mount, is referred to by collectors as the "Fat Focus". The inner barrel is stamped "Patent Appld For", but I have yet to locate a patent or patent filing to determine what design features were covered. One could assume the drive's internal design was addressed, and possibly the manner in which the elements are mounted.
Reportedly, several hundred of these lenses were made before the mechanism experienced problems and Harrison abandoned the design.
The rear glass element on this "Fat Focus" is sleeved, which is then slid into the barrel and secured by a threaded ring. This design differs from the later C.C. Harrison lens No. 6129 shown below, in which the lens is integral to its threaded mount. The serial number on this "Fat Focus" is stamped rather than engraved, which appears to be characteristic of Harrison's later lenses.
Sought after by collectors, the "Fat Focus" is rarely seen today.
"Fat Focus" radial drive Conventional radial drive
Half-Plate, Serial No. 2943 Quarter-Plate, Serial No. 6129
Sleeved-style element mount Integrated element mount