OM System M.Zuiko ED 100-400mm f/5-6.3 IS II

This zoom puts distant subjects within easy reach on Micro Four Thirds cameras. The 100–400mm range suits wildlife, birds and outdoor sport, where you often cannot move closer. The small sensor tightens the view further, so distant subjects fill the frame sooner.

Bird photographers and sideline sports shooters are the natural audience for a lens like this.

OM System released this II model in 2025, and it remains in production. The trade-off is light gathering. The maximum aperture is modest and varies across the zoom, so this lens favours bright outdoor light.

At 2 lb 7.7 oz (1125 g), the lens carries some weight on a small mirrorless body. The barrel measures 8.11 in (206 mm) long and 3.4 in (86.4 mm) wide. Even so, handheld use and walking with it stay realistic. A screw-in filter must match the 72mm thread.

The 100–400mm range covers two very different framing choices. At 100mm you can include habitat around a perched bird or an athlete and some pitch. Zoom to 400mm and distant action fills the frame, whether that is a raptor overhead or play at the far end of a field.

The maximum aperture starts at f/5 at 100mm and ends at f/6.3 at 400mm, so bright conditions suit it best. In forest shade or at dusk you will need a higher ISO or a support. Backgrounds stay fairly busy behind distant subjects, because a modest aperture separates them less. Our optics score for this lens is 53 out of 100.

Close work is possible. The lens focuses as close as 4.3 ft (130 cm), close enough to photograph a butterfly or a small bird that tolerates you. Maximum magnification reaches 0.29x, so small subjects can fill a good part of the frame.

Nine aperture blades shape the opening. When you stop down, the blades keep the aperture close to round, which helps backgrounds render smoothly behind an isolated subject.

The built-in image stabilization matters most at the long end. It steadies the camera at zoom settings where small hand movements are magnified along with the subject. It cannot freeze a running animal's motion, but handheld framing at 400mm becomes practical.

Weather sealing guards the lens against dust and moisture. The fluorine coating on the front element sheds water and oil, so drizzle and fingerprints wipe away easily. Together they suit long days in a damp hide or a dusty sideline.

A zoom lock stops the barrel from creeping down when the camera hangs at your side. This section carries a score of 96 out of 100.

The optical design uses four ED elements and two Super ED elements. Low-dispersion glass helps reduce chromatic aberration, where colours focus differently and leave coloured fringes along high-contrast edges. A bird against a bright sky is the kind of subject where such fringes show. Focusing is internal, so the lens holds its length and does not extend while you focus.