One of my main reasons for switching to mirrorless over a decade ago was to shoot with any number of vintage lenses. Early on I discovered that rangefinder lenses could pose a problem — rear elements and housing parts could protrude deep into a mirrorless body. Depending on the lens and body combination, a conflict between the two could be catastrophic: the lens could come into contact with the shutter or even worse, the sensor.
I discovered this problem with a 28mm Contax G lens and my GH1. When I attempted to mount the lens, the pair of plastic tabs designed to protect the convex rear lens element smacked into the front shutter and sensor housing. A little cutting later, the tabs were gone, and I could mount the lens. The clearance between the rear element and shutter was tight, but no conflict.
Collapsible lenses create a different problem. Before the pandemic, I picked up a vintage collapsible 50mm Leica Summitar in San Francisco. Studying the lens within the M to E adapter revealed that when it was collapsed, the metal ring around the rear element would protrude into the A6500/A6600 body about 1mm too far and rub against the plastic that enclosed the sensor.
While technically not a problem, if the lens was crushed while mounted, the metal ring could cause serious sensor damage as the frame — rather than the mount — would take the hit. The quick fix at the time was to wrap a rubber band around the extended lens barrel to reduce the retraction distance. Fast forward to 2022 and the rubber band failed; time for a better solution.
The rubber band option did offer two key things: 1) occupied space on the lens barrel that would prevent the lens from collapsing to its full extent and 2) offered a bit of a cushion in case the lens itself was impacted while collapsed. The problem with the rubber band is that it deteriorated quickly. The alternative was to measure the diameter of the barrel and locate an appropriate rubber o-ring that could stay attached to the lens, not interfere with its operation (the rubber band did want to slide into the groves of the lens), provide a solid cushion, and offer more than 1mm of distance between the rear of the lens and the camera body. I found that a #18 o-ring would likely do the trick.
The next step was to get the o-ring onto the lens without taking the lens apart. Fortunately, o-rings are a bit flexible and would likely fit over the lens if gently stretched. First thing was to remove the protective filter housing that I added to the lens as the o-ring couldn’t stretch complete over the filter adapter and the filter itself.
With the filters removed, I could gently roll the o-ring onto the lens starting from one side and stretching it over the front element. I made sure to warm up the o-ring with my hands to help make it a little more pliable.
Once the o-ring was rolled on, I reattached the filter and snugged the o-ring up to the backside of the front element so it didn’t create unnecessary friction during lens collapse or extension.
With the o-ring in place, I collapsed the lens and you can see the added distance on the lens barrel. The lens now stops well short of the plastic frame that protects the sensor inside of my Sony A6600.
And there you have it. A simple fix for a potentially catastrophic problem. For those who are interested, the adapter on the A6600 is a Fotodiox DLX Stretch Leica M to Sony E. The rubbing shown on the image occurs with all of my M to E adapters.