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 p.1 #9 · 5D mirror collision with Mamiya 21mm f/4 M42 lens - is it harmful? | |
If you have a lot of lenses that do this, modify the mirror. If you have only one or two, consider modifying the lens. I did the latter with my Leica 28mm f/2.8. That's a relatively expensive lens (though not when compared to other Leicas that sell well over $2K and more). I sanded down the rear shroud till the mirror cleared. By chance, the mirror cleared before I ran out of metal to sand, so that is not going to work for all lenses clearly. I repainted the bare metal on the end, and it looks and functions fine. Personally, I believe this lens is now worth more than I paid for it, because it is now functional on the 5DII, which is definitely not typical.
On whether you do damage when the mirror hits. Since there have been reports of mirrors coming unglued on some 5D's, I suppose the cumulative stress on that glue joint could displace the mirror off its mount eventually. But of more immediate concern is what I believe to be the short term tendency for the mirror to become misaligned. After a whack or two of that mirror, what appears to be in focus in the viewfinder may not prove to be in focus on the sensor and the file. I think this does happen, making images subtly out of focus. On the 5DII, it's possible to check the discrepancy between the manual, viewfinder focus and the sensor focus by alternating between the viewfinder and live view. If they are not in agreement, either you need to microadjust the lens, or if that was previously done, the whack of the mirror on the back of the lens has probably misaligned the mirror temporarily. My guess is that to the degree the mirror mechanism has some flex, that mechanism probably eventually rebounds to its original positioning over some indefinite period of time (like less than a day, maybe less than an hour, just depends). This is my hypothesis, as I have not seen anyone writing about this, and I suggest this because it seemed to fit the facts for me prior to shaving the Leica. There would be a brief time period where all my lenses appeared to need more microadjustment, and it subsequently dawned on me that the Leica had likely been the culprit. In reality, they did not need any readjustment, as I came to realize over time.
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