Bausch & Lomb Optical Co. (Rochester, NY)

 

Plastigmat Variation 2 (ring iris), c.1904-1920's

 

 

The Anastigmat Lens as and Aid to Artistic Photography, Bausch & Lomb Optical Co., 1906, pp. 23-25

 

Notes:  This lens was not in the 1898 catalog, so was first offered about 1900.  When introduced, it sported a lever-controlled iris diaphragm (Bausch & Lomb Plastigmat Variation 1 (lever iris)).  By 1904, the lens had acquired a ring iris (Bausch & Lomb Plastigmat Variation 2 (ring iris)), which is less prone to damage than the lever iris.  For either variation, there is no provision for a lens shade (screw threads on the front edge of the lens).  A lens shade is the front continuation of the barrel of the lens, usually a slightly greater diameter than the lens itself.  The purpose of the lens shade is to minimizes flare (stray light not contributing to the image).  Prior to 1900, almost every lens had a lens shade.  It may be that the anastigmats, introduced about 1890, were not as prone to flare.

References:
The Anastigmat Lens as and Aid to Artistic Photography, Bausch & Lomb Optical Co., 1906, pp. 23-25
Premo Cameras, Rochester Optical Co. (Rochester, NY, dated 1907, p. 54

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