Is it focussing though? The ring doesn't move as you focus, only when you engage it manually does it lock into the focus mechanism and allow you to move it. If it isn't focussing check to ensure the lens is set to M/A on the 'M/A - M' switch. Does the D5100 have a focus selection lock? I don't think it does but if it has one that might be engaged.
What is your answer?
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How old is your lens? The Nikon D5100 doesn't have a built in focus motor, so older Nikon lenses that don't have a built in focus motor in them will not work with your camera.
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Visitor7 months ago Sanjoy-Dasits a brand new lens just purchased (AF-S DX NIKKOR 18-105mm). -
Beginner I7 months ago Rgu-RaghuNIKKOR 18-105mm AF-S DX IF Is Internal focusing lens and it has an internal focus motor[Since its AF-S IF]. So the ring wont move but it focuses according to the auto focus mechanism
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