mis-aligned datum mark on Summitar

[golcarlily]

Advertisement (gone after registration)

I recently purchased an f2 Summitar which had just been serviced by Leica according to it's owner.

 

I checked with leica in Milton Keynes U.K. who confirmed that this was so. I have since discovered that the datum mark on the front lens element surround does not indicate the correct aperture.

 

With lens fully stopped down the mark is opposite f11 (should be f16) and fully open the datum points to an area of no-mans land past f2.

 

Leica suggested stopping it down fully (which they promised would be f16 as it would have been checked at servicing) and putting a pencil mark on the lens barrel to indicate correct aperture.!!

 

Is this a common problem ?

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[doubice]

It could be that the front lens cell has been overtightened. When that happens, the 'datum mark' moves past its correct position and one ends up with what you have on your Summitar.

 

I have seen it before, on Summitars where fog was removed from behind the front lens cell. You can try unscrewing the front cell and screwing it back again, aligning the datum mark with f:2 (the lens fully opened of course). See if the front cell is tight enough when the datum mark and f:2 are aligned. That should cure it.

 

Best,

 

Jan

[golcarlily]

It could be that the front lens cell has been overtightened. When that happens, the 'datum mark' moves past its correct position and one ends up with what you have on your Summitar.

 

I have seen it before, on Summitars where fog was removed from behind the front lens cell. You can try unscrewing the front cell and screwing it back again, aligning the datum mark with f:2 (the lens fully opened of course). See if the front cell is tight enough when the datum mark and f:2 are aligned. That should cure it.

 

Best,

 

Jan

 

Thanks

I have done what you suggest. Interestingly the datum does not now align with both

ie if I align it at f16 it is out at f2 and vice versa ! But by much less than before.

The diaphragm control is now much smoother and freer. Before, when stopping down I sometimes had to hold the the lens barrel to prevent the whole thing rotating as if in readiness to collapse it.

[doubice]

Thanks

I have done what you suggest. Interestingly the datum does not now align with both

ie if I align it at f16 it is out at f2 and vice versa ! But by much less than before.

The diaphragm control is now much smoother and freer. Before, when stopping down I sometimes had to hold the the lens barrel to prevent the whole thing rotating as if in readiness to collapse it.

 

When aligned at f:2 the aperture ring will always turn slightly past f:16 - this is normal, at least on my Summitars. Your starting point for correct alignment should be datum mark aligned at f:2.

 

Best,

 

Jan