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Old Mar 8, 2015, 5:01 PM   #1
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My brother in law's canon 70-200 2.8f lens won't focus in manual nor in auto focus mode. The lens filter is stuck and will not come off.

Is it possible that the lens filter being so tight (and is been on that lens for many 60,000 shots) that the filter had caused the focus motor or some part of the focus system to malfunction?

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Old Mar 8, 2015, 5:37 PM   #2
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If he can't focus manually, then it has nothing to do with the filter or the focus motor.
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Old Mar 8, 2015, 6:37 PM   #3
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The thing that made me wonder if there was a connection is this: When I put a filter on my camera lens, I don't crank it on as tightly as possible. But when I take it off, I must apply more pressure to remove it than it took to put it on.

So I was thinking that maybe the focusing action was causing the filter to tighten.

Is the filter tightening or is that just my imagination?

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Old Mar 8, 2015, 7:02 PM   #4
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In general, lenses don't rotate when they focus. So the action of a lens focusing wouldn't tighten a filter.

What you're describing can be caused by a number of circumstances.

First, metals expand and contract with changes in temperature. When you're holding something, the heat from your hand warms it up (Steel: 0.000006 inches/inch/F, Brass: 0.000010 inches/inch/F, Aluminum: 0.000012 inches/inch/F) so it gets bigger, but after it's been on the lens a while it cools off and shrinks. So it's tighter when you take it off than when you put it on.

Also, some metals can bind, especially cuprous metals (Brass, Bronze and Copper), so a filter with a brass mounting ring may be harder to remove than a filter with a mounting ring made with some other material.
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