07-09-2013 09:57 PM
The manual focus ring on my Canon 18-135mm EF-S spins freely whether the switch is in the AF or MF position. It does not alter the focus. Auto focus works well. Another zoom lens seems to allow manual focus without difficulty. What have I overlooked?
Solved! Go to Solution.
07-10-2013 12:22 AM
Is this the new STM version or the older non-STM version of the 18-135? This will make a difference in how the focus ring works.
If it's the non-STM version (original 18-135) then you should _not_ attempt to focus the lens manually when the auto-focus switch is in the AF mode.
If it's the STM version (new 18-135) then you can rotate the focus ring whether the auto-focus switch is in the AF or MF position (but it wont focus unless the camera is powered on and not sleeping. E.g. half-press the shutter to wake it and the focus ring will work.)
Most USM lenses (there is no USM version of the 18-135) allow the focus ring to be turned whether the camera is in AF or MF mode. The ring is basically a like a mild clutch and it has some deliberate slip built in -- and those focus rings will just keep turning and turning... there is no hard stop for the ring.
08-01-2013 06:40 PM
You don't have to press the shutter to 1/2 to manually focus the lens. At 18MM focus is esentially infinity and nothing much happens when turning the focus ring. Zoom to something 10-15 feet away and the focus ring (in MF) will take up to 2 turns of the ring to get the subject in focus.