p.1 #2 · What are the various possible lens problems?
scratches/dings on barrel
scratches/chips on glass elements
barrel alignment(for non-internal zooms)
contact points
not just loose, but uneven tightness on zoom/focus rings
filter threads
p.1 #5 · What are the various possible lens problems?
How about "too many" and "too few"
And L fever. Don't forget L fever.
Also collimation or lens alignment issues that tilt the plane of focus.
IS problems.
Switch or button problems.
Self-zooming due to poor mechanical gearing for the weight involved.
Problems with the electronics (computer, motor, servos, etc.).
Internal cables coming adrift (and perhaps being damaged by or blocking moving parts).
Dust or other muck floating around inside (usually looks worse than it is).
