Front lens element loose, how much of a problem?

[JamesFromSydney]

I have a 40mm Minolta M-Rokkor f2 lens (on a Leica CL), and have noticed that the front lens element appears to have come loose. If I tip the lens over, it makes a click noise. I've isolated the source of this noise to the front glass element, which appears to be able to move perhaps half a mm in and out.

Not sure what caused this -- I don't baby the camera, but also don't abuse it.

Firstly, any ideas on whether this is likely to be a serious problem for shooting purposes? i.e. will this impact the image quality?

Also, anyone know if this is common for this lens? I got the M-Rokkor instead of the Summicron-C because it was reportedly better wrt coatings and otherwise identical, but I wonder if the Leica construction might be significantly better in some way.

I need to decide whether it's worth getting repaired, needs to be repaired at all, or whether I should get a different brand of lens.

 

[ZeissFan]

Try using your fingers or perhaps a pencil eraser to see if you can tighten the front retaining ring (the face ring -- the one with the writing). If it has slots, you could use a spanner wrench (or a flat screwdriver) to see if you can gently tighten it.

You never want a loose lens element. Aside from not focusing properly, you also don't want it banging around, which in some instances could lead to chipping ... although I don't think this would happen to your lens.

 

[JamesFromSydney]

ZeissFan: thanks, got me headed in the right direction. The front retaining ring was not loose, so I unscrewed it to have a look -- it's actually made of plastic and appears to be cosmetic (although possibly protects against dust).

I could then access the front element, which had unscrewed itself slightly, so I tightened that up, replaced the front ring and the problem seems to be solved!

 

[alex.wheatley]

Sorry to interrupt this thread but wondered if someone could help I have a 40mm voigtlander thats front element was loose, it has a focus shift problem and when I tightened the element the traditional way (clockwise) the focus shifts remained so out of curiosity I then turned it anticlockwise and it locked in that position too minus the focus shifts is this normal for a lens to have a reverse thread on the front element or have I put something somewhere that shouldn't be and it may loosen up again?
Thanks
Alex

 

[Chriscrawfordphoto]

Sorry to interrupt this thread but wondered if someone could help I have a 40mm voigtlander thats front element was loose, it has a focus shift problem and when I tightened the element the traditional way (clockwise) the focus shifts remained so out of curiosity I then turned it anticlockwise and it locked in that position too minus the focus shifts is this normal for a lens to have a reverse thread on the front element or have I put something somewhere that shouldn't be and it may loosen up again?
Thanks
Alex

What do you mean by Focus Shift? Do you mean it always focuses incorrectly, or do you mean it focuses correctly at f1.4 and the focus changes as you stop down? That is what focus shift actually is...The 40mm Nokton is well known for having it, it is a side effect of the Nokton's design and cannot be fixed.

 

[alex.wheatley]

Sorry I did not mean focus shift, I meant focus inaccuracy, basically whatever a calibrated rangefinder told you you were focusing on you were actually focussing past that, from my tests this was linear, i.e the lens focused beyond infinity and at any given distance what the rangefinder and lens markings said was in focus was actually before the point of focus. So it seems that the way the front element is screwed affects the whole position of focus, obviously however since I do not have a great understanding of optical design the fact that I have been able to change focus by only moving one element makes me hesitant of what else I might have changed even if doing so appears to remove my problem! Just to be clear I have been checking this using both an M6 (with a recently calibrated rangefinder) and an olympus e-p1 which has an adaptor on it which I have shimmed to give the correct film to flange distance hence I could see the lens went beyond infinity due to the fact that any other M lens I put on the mount would focus on infinity when it hit the stop whereas the 40 went beyond, I then used callipers and the M6 to confirm that when the lens was at its infinity stop its cam was indicating the correct position for infinity on a rangefinder (removing the possibility that the lens just went beyond infinity but the rangefinder would read infinity when it was focused correctly before its stop). Sorry for being long winded and confusing just want to give as much detail as possible.
Thanks
Alex