Aperture ring on M lenses made in Canada

[Robert Ridyard]

I own three Summicrons: 35 mm (Canada),
50 mm (Germany) and 90 mm (Canada). The white dot on the aperture ring
on both Canadian lenses is off-centre and does not align with the
center of the depth-of-field scale. In both cases, the white dot is on
the side of the lens barrel, i.e. the side of the camera where the
film-advance lever is located. This is not the case with the German-made
lens, where the white dot appears on the top of the barrel and is
aligned with the depth-of-field marker. Question: were the Canadian lenses made this way? (I am not the original owner, so I don't know if any work was performed on them.)

[budrichard]

Originally Posted by Robert Ridyard

I own three Summicrons: 35 mm (Canada),
50 mm (Germany) and 90 mm (Canada). The white dot on the aperture ring
on both Canadian lenses is off-centre and does not align with the
center of the depth-of-field scale. In both cases, the white dot is on
the side of the lens barrel, i.e. the side of the camera where the
film-advance lever is located. This is not the case with the German-made
lens, where the white dot appears on the top of the barrel and is
aligned with the depth-of-field marker. Question: were the Canadian lenses made this way? (I am not the original owner, so I don't know if any work was performed on them.)

I looked at three M3 vintage Summicrons I have. A DR, 35RF and 90mm. The DR and RF were made in Germany and the 90mm in Canada. On the DR and RF the dot that I think you are referring to is black and does not line up with the center of the depth-of-field scale. The 90mm is of different construction.
On all my current generation ASPH lenses, the white dot does line up with the DOF scale.-Dick

[wizard]

The dot (white on black lenses, black on chrome lenses) should always align with the center of the depth of field scale. If it doesn't, the lens head may have been screwed in too far at some point or is not screwed in far enough. Note that on most current lenses you are not supposed to screw the lens head in or out. When mounting and demounting the lens from the camera, one should not hold the lens at the lens head, as especially the mounting operation involves applying a sometimes considerable torque to the lens, which may cause the lens head to move relative to the lens barrel.

On some older lenses, for example the DR Summicron 50, it was possible to unscrew the lens head for use with e.g. the Visoflex. When refitting the lens head it should be screwed in until the dot lines up with the center of the depth of field scale.

Best,

Andy