Carl Zeiss Jena Flektogon 20 mm f/ 4 Lens Manual
Zeiss Biotar 58mm f/2 Disassembly – Semi Automatic Style for Exakta
An adventure in lens repair by K. Rhoads
This is the story of Biotar 4427070, a lens with a troubled past, described on eBay as “in good shape but
could probably use a professional cleaning.” The release was stuck, the aperture blades were clean but
binding, the cocking mechanism would not reliably cock, the front assembly was not concentric with the
rear assembly, a ding in the focusing ring left wipe marks on the aperture ring, focusing was stiff and gritty,
the bayonet tabs were bent, and there was fungus in the lens. On eBay, that’s what passes for “good shape.”
could probably use a professional cleaning.” The release was stuck, the aperture blades were clean but
binding, the cocking mechanism would not reliably cock, the front assembly was not concentric with the
rear assembly, a ding in the focusing ring left wipe marks on the aperture ring, focusing was stiff and gritty,
the bayonet tabs were bent, and there was fungus in the lens. On eBay, that’s what passes for “good shape.”
The Biotar is described in various places as originating in 1911 or 1932, as a variant of a Voigtlander
Petzval design. It is also described as a 6-element “double Gauss” design. While I did not perform a
complete disassembly, my guess is that this is a semi-symmetrical design: convex-plano objective,
achromat doublet, aperture blades, achromat doublet, plano-convex rear element.
Petzval design. It is also described as a 6-element “double Gauss” design. While I did not perform a
complete disassembly, my guess is that this is a semi-symmetrical design: convex-plano objective,
achromat doublet, aperture blades, achromat doublet, plano-convex rear element.
The Biotar is praised by Wrotniak as having “a large following of photographers who describe its imaging
as ‘deeper,’ ‘more three-dimensional,’ or simply ‘better’ than that of most other lenses … Indisputably,
Biotar’s imaging is slightly softer than Tessar’s, while not degrading the perceived image sharpness, and
this may be the reason that so many photographers (including myself) like it a lot.”
(http://www.wrotniak.net/photo/exakta/lenses.html)
as ‘deeper,’ ‘more three-dimensional,’ or simply ‘better’ than that of most other lenses … Indisputably,
Biotar’s imaging is slightly softer than Tessar’s, while not degrading the perceived image sharpness, and
this may be the reason that so many photographers (including myself) like it a lot.”
(http://www.wrotniak.net/photo/exakta/lenses.html)
Part 1: The Focus & Release Assembly
Remove the release button with four screws. Can lubricate this unit without further disassembly. Clean and
then graphite lube. Be sure the action is smooth, and reassemble.
then graphite lube. Be sure the action is smooth, and reassemble.
Focus to infinity, set to f/4, and mark the way the lens should rejoin before separating. Mark the position of
the top of the focus barrel at infinity with a line on the aperture ring. From the back of the lens, remove the
thick spanner ring (thickest and furthest outside of the 3 visible spanner rings).
the top of the focus barrel at infinity with a line on the aperture ring. From the back of the lens, remove the
thick spanner ring (thickest and furthest outside of the 3 visible spanner rings).