Review: OM System / Olympus M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO

Before we begin, I want to disclose that this lens was loaned to me by OM System Netherlands—kudos to them for their outstanding service. They had no input in this review, nor did they preview it before publication. Everything you're about to read is based entirely on my own hands-on experience, built on years of working with a wide range of telephoto lenses. Over the past few weeks, I’ve put this lens through its paces, shooting several thousand images in the field. Let's dive in.

Build Quality – ★★★★☆ (4/5)

The moment you pick up this lens, its premium build quality is immediately apparent. If you're familiar with the Olympus 300mm f/4 PRO, you'll recognize the same robust construction—everything from the lens mount to the hood feels meticulously engineered. Buttons have a satisfying click, and the addition of strap lugs is very welcome for safely carrying the lens.

The focus ring is smooth and precise, but I did deduct half a star due to the zoom ring. It feels somewhat coarse, and worse, when recording video with an on-camera mic, the zoom operation produces a noticeable squeaking sound. I’m not sure whether this is specific to this demo copy or a general trait of the lens—I’ll definitely be asking OM System about it.

Nikon Z 180-600mm f5.6-6.3 vs Olympus/OM-system M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO

Handling – ★★★★½ (4.5/5)

Let’s start with one of this lens’s biggest strengths: its weight. At just 1875g, it’s incredibly well-balanced when paired with a camera like the OM-1. The weight distribution is closer to the lens mount, making it feel even lighter in hand. Compared to something like the Nikon Z 180-600mm f/5.6-6.3 (2140g), the OM 150-400mm feels significantly more nimble, especially due to that smart weight distribution.

With an equivalent focal length of 800mm (full-frame) and a built-in 1.25x teleconverter taking you to 1000mm, the reach is nothing short of phenomenal. Add in the MC-14 or MC-20 teleconverters, and you can reach a staggering 1400mm or 2000mm equivalent—all handheld thanks to OM’s superb Sync IS stabilization system (lens + body working together).

The zoom ring has a short throw from 150mm to 400mm, which makes subject tracking while zooming feel natural and efficient. However, the manual focus ring is placed near the front of the lens, which I find less convenient. I'd prefer it closer to the mount—like on the Nikon 180-600mm—making manual focusing much more accessible while shooting.

Side controls and switches include:

Focus Limiter Switch: Useful for boosting AF speed. Set it from 6m–∞ when shooting distant wildlife, or 1.3m–6m for semi-macro work (e.g., dragonflies or insects). Yes, it really does focus as close as 1.3m—even at 1000mm—which is just insane and makes this a superb tool for shy, skittish subjects.
AF/MF Switch: Handy to have, though I personally preferred the pull-back clutch mechanism on the 300mm f/4 PRO for quicker switching.
IS Switch: Turns image stabilization on/off. Disabling it will also turn off the IBIS in the camera body—helpful when working on a tripod to prevent micro jitter.
L-Fn / Preset Button: Customizable via the camera menu. I had it assigned to AF-On so I could focus while holding the lens close to the ground—very convenient when your camera’s AF-On button is out of reach.
Sound On/Off Switch: Disables audio feedback for AF confirmation—great for not disturbing wildlife, so I kept this off almost all the time.

Olympus/OM-system M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO on a OM-1 Mark2 — Olympus/OM-system M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO

The strap lugs are more than just a nice touch—they’re essential. With large telephoto lenses, it’s best to think of the camera hanging from the lens, not the other way around. I’ve seen mounts break in workshops from improper carrying, so I always appreciate well-placed lugs.

The lens hood uses a screw-clamp mount—another sign of a truly professional-grade telephoto. It comes with a soft lens cap (velcro closure), and the hood interior is flocked with felt to prevent flare.

The tripod collar features click stops at every 90°, great for switching between portrait and landscape quickly. That said, it can be a drawback when filming video on a tripod—you sometimes need finer adjustments, and the clicks can get in the way. I’d personally prefer an option to disable this feature.

Finally, the built-in 1.25x teleconverter is fantastic. It engages with a quick flick of a lever and can be locked in place to prevent accidental activation—fast, easy, and extremely useful.

Overall, handling is superb, with only a couple of minor quirks (focus ring position and collar detents) holding it back from perfection.

Optical Performance – ★★★★½ (4.5/5)

This lens is simply outstanding in terms of sharpness and image quality. Even with the built-in 1.25x teleconverter engaged, it maintains excellent sharpness wide open. That’s a rare feat for a zoom lens, especially one with this kind of reach.

Nikon Z8 with de Nikon Z 180-600mm Left and de OM-system OM1 mk2 with de OM-system 150-400mm f4.5 pro on the right. — On the left: Nikon Z8 with the Nikon Z 180-600mm lens.
On the right: OM System OM-1 Mark II with the M.Zuiko 150-400mm f/4.5 PRO.
The subject was approximately 5 meters away. Both lenses were used wide open—f/6.3 for the Nikon and f/4.5 for the OM System.
Shutter speed was set to 1/1000s, and both cameras were used at their lowest native ISO.
The Nikon was set to 600mm, while the OM System was at 400mm (equivalent to 800mm full-frame). To match the framing, the Nikon image was cropped to achieve the same magnification.

Compared directly to the Olympus 300mm f/4 PRO, the prime is slightly sharper and has a smoother bokeh. But thanks to the longer focal length of the 150–400mm, you get stronger background compression and subject separation—so in practice, the difference is minimal, and in many cases, even favorable for the zoom.

This is a pro-grade zoom through and through.

Autofocus Performance – ★★★★½ (4.5/5)

AF speed is top-tier. While the 300mm f/4 PRO still has a slight edge (smaller glass, faster movement), the 150–400mm is no slouch. It's quick, accurate, and perfectly capable of tracking fast-moving wildlife. When paired with the OM-1 or OM-1 Mark II, the lens really shines in demanding scenarios.

Downsides – or better yet: Room for Improvement

Let’s be honest: this lens is a masterpiece, purpose-built for professional wildlife and nature photographers. It would also excel for distant landscapes. What got me most excited is how well-suited it is for capturing high-quality wildlife video… on paper, at least.

The issue is not with the lens, but with the ecosystem around it. As of now, the OM-1 (Mk I and Mk II) doesn’t deliver the video quality I need, especially when compared to something like the Nikon Z8 with the 180-600mm or a 600mm f/4 prime. And don’t get me started on the video autofocus—manual focus is almost a necessity.

Yes, you could pair the lens with a Panasonic GH7 or similar for better video quality, but you’d lose Sync IS, one of the biggest advantages for handheld shooting.

Come on, OM System—professional-grade 4K video is a must in today’s wildlife photography and videography world. I’d love to rewrite this section one day, when the OM-1 Mark III arrives with the video capabilities this lens truly deserves.

Conclusion: Versatile, Professional, and Packed with Potential

The OM 150–400mm f/4.5 TC1.25x IS PRO is an extraordinary lens with unmatched versatility. For still photography, it’s a dream—offering impeccable image quality, incredible reach, and near-flawless handling. For hybrid shooters who also need serious video capabilities, the system isn’t quite there yet… but hopefully, that’s just a matter of time.

If you're a wildlife photographer, this lens could easily become the crown jewel of your kit. It’s a rare blend of portability, power, and precision. A truly professional tool with almost limitless possibilities.

Review: OM System / Olympus M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO