“Hoh & Hahne”

Data:

• The slide rule was probably made by Nestler, because the paper on the back is the same as on Nestler types.
• The cursor has only one line.
• “The company Hoh & Hahne (later known under the brand name HOHLUX) was a historic, now liquidated, manufacturer of photographic equipment and reproduction technology in Leipzig. It no longer exists as an active company.”
  Hoh & Hahne was merged into the VEB Polygraph Reprotechnik in 1962. Andries de Man

Questions:

1. What were the A and B Scales used for?
   They solve the thin lens equation

   1 f

   =

   1 A

   +

   1 B

   with f = focal length (46 cm, as indicated at the far left)
   A = distance from the lens to the photographic plate
   B = distance from the lens to the object
   Try it yourself: set an A or B value and compare the A-B pair with the slide rule.
   A=
   B=
   Note the A-scale runs in a direction opposite the B-scale.
   In Hoh & Hahne camera's the distance between lens and photographic plate was variable. Andries de Man