W.A. Symm lens

[Sheldon Crook]

I have an old brass lens which is stamped "W.A. Symm No. 5" and "U.S. Opt. Co.". It has a wheel which can be rotated to bring various apertures into the lens field, ranging from f16 to f256. Can anyone tell me anything about this lens and its usage? There are no other marks to indicate focal length or anything else.

[Ernest Purdum]

The U.S. Opt. Co. must have been a rather obscure outfit, since there is no reference to them in the Lens Collector's Vade Mecum. I can't tell you anything specific, but I can give you a few generalities.



Although "Symmetrical" could of course apply to an anastigmat, your lens with its f16 maximum aperture and wheel stops, was probably made before anastigmats came into frequent use. It is very likely a wide angle version of the Rapid Rectilinear or Aplanat form , a two element achromat pair on each side of the diaphragm.



At the time your lens was presumably made, it was very common not to mark the focal length on the lens, but simply give the size number. Unfortunately, there was no standardization here, so you had to have the maker's list or a catalog in order to know what focal length "No. 5" indicated.



The "256" of the smallest aperture marking almost surely indicates use of the "Uniform System" of aperture markings. The corresponding "f" stop is f64.

[Mike Phifer]

Sheldon, I agree with Ernest's comments that your lens is likely to be a Rectilinear or Aplanat. (Same design: Steinheil (Aplanat) and Dallmeyer (Rectilinear) simultaneously and independantly invented this lens design in 1866.) This lens is historically reguarded as one of the most significant objectives ever made. Kingslake states, "This design came midway between the invention of photography in 1840 and the introduction of the Anastigmat in 1890, and lenses of this type were fitted to all of the better cameras for nearly sixty years, a record scarcely surpassed by any other lens. (R. Kingslake, A History of the Photographic Lens, 1989)"

The use of the Uniform Scale (U.S.) system for aperature markings helps to date the lens. This system was developed around 1890. Based on the scale it is possible that the lens could also be an Anastigmat built under liscence by Zeiss, but more likely an Aplanat. The apature conversion for the U.S. system are f 16 = U.S. 16, f4= U.S. 1, f 64 =U.S. 256 the conversion formula is U.S.= f^2 / 16. (f squared divided by 16) .

I hope this helps... Mike