lens mount on Contax iiia

Discussion in 'Leica and Rangefinders' started by ron_mckinney, Aug 8, 2014.

  1. I have a Contax iiia and 21mm Biogon f4.5 lens. When the lens is mounted the red dot and the black arrow focus index marks are not at top dead center but are off to the right (looking into the lens) a little. Not all the way to 1:00 but at about 12:30. Is this how the lens should mount? I would expect the red dot and focus index to be precisely at the top but I've never had one of these before.
  2. AJG


    Congratulations on the Contax and the 21 mm Biogon--it's a great lens. It should mount with the focusing index mark at dead center. Don't apply a huge amount of force, but perhaps a little more will bring it to where it belongs. My 135 Sonnar requires a bit more effort to get to the right position than my other Contax lenses (Zeiss and Nikon RF) but it does get there.
  3. Ron
    It so happens I am using my Contax IIA and 21 Carl Zeiss Biogon F4.5 for the last 10 days...until I use up two rolls of film.
    Before you mount the lens you need to make certain that the red dot on the inside most portion of the lens lines up with the red dot on the mounting boss of the lens.....the portion of the interior part of the lens (inner most element) will rotate to make this happen....
    then make certain the camera body is focused to infinity (via the focusing wheel) and make certain that the lens is focused to infinity before you attempt to mount the lens....
    then carefully stick the lens in the body in a position so when first inserted the red dot on the flange of the camera body lens mount lines up with the red dot on the lens mounting flange....
    when inserted full, twist the lens counter - clockwise (looking at the camera) until the lens mount clicks. Now the red dot on the lens should be at the 12:00 position. If it is not, you didn't make certain the camera body was focused at infinity before you tried to mount the lens.
    Mounting it like you have will sometimes make the lens very difficult to take off without damaging the body or the lens....if it gets to that point, it is time to send it to a technician to dismount the lens without casuing further damage.
    Every time you remove a lens (other than the 50mm) the camera's focusing collar will have to be brought back to infinity before you mount another lens (also pre-focused to infinity).
    Congrats on the 21mm F4.5 Carl Zeiss Biogon, this lens, introduced in 1954, is probably one of the top five lenses ever developed for photographic purposes. It is capable of helping you produce stunning results.
    gene_sparks|1 likes this.
  4. How to remove lens from Contax IIa
    There is one red dot on the Contax front plate at upper right side
    There is also a red dot on the lens flange
    The two red dot must be align (the lens is focus at infinity)
    Press down the spring catch on the lens flange, twist the lens barrel to remove the lens
  5. I use LTM cameras (Leica and Canon), Leica M, Contax, and Nikon. During days of LTM, the Contax mount had advantages. However, the Leica M revealed how cumbersome the Contax mount was. I can change lenses on an M without looking, but doing so on a Contax is too fidley. The lens mount alone can explain the demise of other rangefinder cameras with introduction of M3, especially for press photographers. Yet, I do enjoy shooting with all of them.

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