The rear ring is not a zoom ring — it is a speed control for a motor. Turn it a little and the lens zooms slowly; turn it more and it zooms fast; let go and it stops wherever it got to. The trick almost nobody knows: in autofocus mode the front ring becomes a fine zoom control, and it behaves like a normal zoom ring.
rear = coarse servo front = fine zoom in AF front = focus in MF
Why the zoom feels wrong at first
- There are no focal-length markings anywhere on the barrel. You cannot tell where you are by looking at the lens; you read it on the screen.
- Ring position means nothing. The ring rocks through about an eighth of a turn and controls rate, not position — which is exactly why people overshoot their framing constantly.
- Two zoom speeds depending on how far you turn, essentially silent apart from a faint buzz.
- It retracts for carry and extends about 2 cm on power-up. You wait for that before the first frame.
The workflow that fixes the zoom
Use the rear ring to get roughly there fast, then the front ring to land the framing exactly. In autofocus mode the front ring is a precision zoom that takes about three quarters of a turn from wide to tele — a completely different experience from the servo ring. Switch to manual focus and that same ring reverts to being a focus ring.
The habit that removes most of the frustration
The lens does not remember your focal length. Power off and it returns to 15 mm — and, more annoyingly, reviewing images makes it retract and reset too. So on this lens, chimping costs you your framing.
If you are working a scene at 45 mm, do not review until you are finished with that setup. Shoot the sequence, then look. That single change of habit removes most of what people blame the lens for.
Menu items worth knowing
With lens firmware 1.10 or later, SET UP > BUTTON/DIAL SETTING > LENS ZOOM/FOCUS SETTING offers ZOOM RING ROTATE (reverse the zoom direction) and ZOOM/FOCUS CONTROL RING (assign the control ring to zoom or focus).
Unverified on the X-M5 specifically
These menu items are documented on earlier bodies with this lens. Whether the X-M5 exposes all of them under exactly these names has not been confirmed here — check your own camera before treating it as fact. Everything above about the two rings is documented behaviour.
Assignment: the two-ring drill
Stand in front of a bookshelf. Using the rear ring only, try to frame exactly three book spines — note how often you overshoot. Now do it again: rear ring to get close, front ring to finish. Then set manual focus and confirm the front ring has become a focus ring. Five minutes here changes how the lens feels for good.