Dropped Lens?

I'm considering buying an expensive used lens that has impact damage to the rear filter threads. What is the down side to buying such lens other than the obvious inability to screw on a filter?

Usually, when the impact was hard enough to dent the rear filter threads, there is a high probability that the glass in the rear lens element was knocked out of alignment.

Ask for a money back guarantee if you find that condition.

Often the only downside is when (if) you re-sell the lens, the value will be lower than if the dent wasn't there. The upside is that you very well might get a good price when you buy it.

Impact can cause damage to the shutter mechanism. I dropped one about a year ago and a few days later the shutter stopped functioning. It required a lengthy and expensive repair.

Pete, a couple of things. Those are not filter threads. Filters on large format lenses belong on the front of the lens unless the lens was designed to have a filter placed in the light path. Once you place a filter behind the lens it will change the plane of focus as well as the optical performance of the lens. Those threads are what are used to put the retaining ring that holds the rear glass in place in the lens itself.
Then an impact can, as mentioned, effect optical alignment, it can also crack the shutter housing which would require a new shutter. Or is can create damage to the shutter that is repairable.

The problem with a dented ring is that it shows mishandling of the lens. That visible damage may only be part of the problem. The lens may have other issues due to rough handling that are not readily visible.

Pete,

What everyone has warned you about is dead right. Then again, I took a chance on a 50mm C style Hasselblad lens with a serious front dent from heavy impact. Turns out to be one of the sharpest lenses I use and the shutter works perfectly.

You will only know for sure after thorough testing of the shutter and by running a few sheets of film with this lens.

Thanks for the input! There is enough rumblings from the bass section to warn me off - Thanks

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Originally Posted by Pete Suttner

expensive used lens that has impact damage to the rear filter threads

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There should be no such thing as that :D

Dented lenses are 'bargain' lenses. All the ones I have work fine but I wouldn't pay more than the shutter is worth.