Intro

Before we begin, I want to disclose that this lens was loaned to me by OM SYSTEM Netherlands. A big thanks to them for their outstanding service and support. They had no input in this review and did not preview it prior to publication. Everything you read here is based entirely on my own field experience, built up over years of working with a wide range of telephoto lenses.

Over the past few months, I’ve really put this lens through its paces, shooting several thousand images in real-world conditions. Let’s dive in.

OM-system by Maikel Lonis — shot on the OM1 mark 2 with the OM-system 150-400mm f4.5 pro.

Build Quality – ★★★★★ (5/5)

From the very first moment you pick up this lens, it is immediately clear that this is a serious piece of equipment. The build quality feels exactly what you would expect from a high-end PRO lens. If you are familiar with the Olympus 300mm f/4 PRO, this will feel like a close relative in terms of ruggedness and overall design philosophy.

Everything feels solid and thoughtfully engineered. The lens mount inspires confidence, the included hood is robust, and the overall construction gives you that reassuring sense that this is a tool built for demanding field work. The buttons are tactile and well-damped, offering a satisfying and precise click. The addition of strap lugs is also a very welcome touch, especially for those long days in the field where security and comfort matter.

The focus ring is excellent. It operates smoothly, with just the right amount of resistance to allow for precise manual adjustments when needed. It genuinely feels refined and well tuned for both photography and hybrid use.

There is, however, a small point worth mentioning from my initial impressions, which I also highlighted during my earlier test period. On the original demo/loaned unit, the zoom ring didn’t quite match the same level of refinement as the rest of the lens. It felt slightly more coarse in operation, and I even noticed a faint squeaking sound when recording video with an on-camera microphone while zooming.

That said, with my own new production copy of the lens, this is no longer an issue at all. The zoom action now feels smooth, controlled, and very well damped—fully in line with the rest of the build quality. Everything operates quietly and confidently, even in video use.

Overall, the impression remains overwhelmingly positive. This is a beautifully built lens that clearly sits firmly in the professional category. It feels like an exceptional piece of engineering, crafted to the highest standards and clearly designed for demanding real-world use.

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 size comparison

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 – ★★★★★ (5/5)

This lens is simply outstanding when it comes to sharpness and overall image quality. Even with the built-in 1.25x teleconverter engaged, it remains impressively sharp wide open. That in itself is a rare achievement for a super-telephoto zoom with this level of reach and flexibility.

What really stands out, and what also becomes very visible in the images throughout this review, is just how special the rendering of this lens is. It produces a very pleasing, almost “prime-like” look that goes beyond pure sharpness alone. There is a certain character in the way it draws a scene that makes images feel natural, three-dimensional, and very engaging.

I personally tend to be a prime lens shooter, especially when it comes to telephoto work. In most cases I have always preferred the rendering and transition of primes over zooms. However, this is one of the very few zoom lenses that comes remarkably close to that prime-like rendering. Not just in sharpness, which is already extremely high, but also in overall image character, microcontrast, and the quality of the out-of-focus areas.

Compared directly to the Olympus 300mm f/4 PRO, the prime still has a very slight edge in absolute sharpness, but only when pixel-peeping at 100%. Even then, it becomes surprisingly difficult to reliably tell which image was taken with which lens. At a practical viewing level, the difference is extremely small.

At 300mm (or roughly 600mm full-frame equivalent), the 300mm f/4 PRO does still offer a slightly more refined rendering with a bit more smoothness in the transitions. But again, the difference is subtle enough that in real-world use it is far less significant than you would expect on paper.

Where this lens really starts to pull ahead is in versatility. Being able to extend beyond 300mm all the way to 400mm, and then engaging the built-in teleconverter to reach 500mm equivalent, completely changes the creative possibilities. At these longer focal lengths, the background becomes noticeably smoother, subject separation increases, and the overall rendering remains impressively consistent.

What is especially surprising is that even at these extended focal lengths, the optical quality does not fall apart in any way. The rendering remains very pleasing, with excellent contrast and beautiful subject isolation. In fact, in many situations the extra compression actually enhances the overall look in a very attractive way.

Of course, the Olympus 300mm f/4 PRO remains a reference point in terms of pure optical perfection at 300mm. But the key takeaway here is that this zoom gets incredibly close, while offering significantly more flexibility and reach. That combination is where it truly shines.

This is a pro-grade zoom through and through, and optically it delivers a level of performance that feels genuinely exceptional.

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 f/5.6-6.3
On the right: OM SYSTEM OM-1 Mark II with the M.Zuiko 150-400mm f/4.5 PRO
**overall rendering of the image.**

(Comparison photo above) The subject was approximately 5 meters away. Both lenses were used wide open—f/6.3 on the Nikon and f/4.5 on 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.

What becomes immediately clear in this comparison is just how closely both systems can perform when used in a real-world scenario like this. Despite the differences in sensor size—45MP full-frame on the Nikon side versus a 20MP Micro Four Thirds sensor on the OM System side—the resulting images are surprisingly similar in overall composition, subject rendering, and background behaviour.

If anything, this test highlights something that often gets overlooked: the lens plays a far more significant role in the final image than many people assume. The two setups produce a remarkably consistent look, with only minimal differences in background rendering. In fact, in this specific case, there is even a slight advantage in background separation and smoothness towards the OM System combination.

In terms of absolute sharpness, the OM System setup clearly comes out on top. Detail rendering on the subject is slightly crisper and more defined, even without any need for cropping to match framing. The Nikon image, while very good, requires a small crop to align the composition, which naturally puts it at a slight disadvantage in this direct comparison.

This side-by-side really demonstrates how much influence the lens has on final image quality. Sensor size and resolution still play a role, of course, but their impact is often less dominant than expected when you are working with high-quality modern optics like these.

Ultimately, this comparison shows that both systems are capable of delivering excellent results, but it also underlines how much the lens defines the character, sharpness, and overall rendering of the image.

Autofocus Performance – ★★★★½ (4.5/5)

Autofocus performance is firmly in the top tier. This lens reacts quickly, locks on with confidence, and feels very well tuned for demanding wildlife and action work.

While the Olympus 300mm f/4 PRO still holds a slight advantage in sheer AF snap—mainly thanks to its smaller glass elements and lighter focusing group—the difference in real-world use is surprisingly small. The 150–400mm is absolutely not a step behind in any meaningful way.

What you get here is a very fast, very reliable autofocus system that handles unpredictable subjects with ease. Subject acquisition is quick, and once locked on, tracking performance remains stable and sticky even with erratic movement. In practical field use, it feels fully capable of keeping up with fast wildlife action without hesitation.

Paired with bodies like the OM SYSTEM OM-1 or OM SYSTEM OM-1 Mark II, the lens really comes into its own. The combination feels tightly integrated, with excellent responsiveness in continuous AF modes and strong subject tracking performance even in challenging conditions such as busy backgrounds or low-contrast scenes.

Where this lens stands out most is consistency. It doesn’t just perform well in ideal conditions—it stays dependable when things get difficult. That reliability is exactly what you want from a high-end telephoto system in the field.

Overall, this is an autofocus system that feels professional, confident, and very well balanced between speed and accuracy. It may not be quite as instantly snappy as the 300mm f/4 PRO in absolute terms, but in exchange you gain far more versatility without giving up meaningful performance.

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… at least on paper.

The limitation here is not the lens itself, but the ecosystem around it. As of now, the OM SYSTEM OM-1 (both Mk I and Mk II) doesn’t yet deliver the level of video quality I personally want, especially when compared to something like the Nikon Z8 paired with the Nikon Z 180-600mm f/5.6-6.3 or a high-end 600mm prime setup.

In video AF specifically, the Nikon system feels more reliable overall. With OM System, I found myself switching to manual focus more often than I would like in certain wildlife scenarios. The good news is that with very usable focus peaking and some practice, manual focusing is actually quite manageable and even enjoyable. Still, in fast-moving animal situations, I sometimes miss the level of “set and trust” autofocus reliability that Nikon delivers in video.

It’s worth noting that for other types of video—especially vlogging or human subject detection—the AF performance is excellent and very dependable. So this feels less like a fundamental flaw and more like an area that still needs refinement for serious wildlife videography. And honestly, I fully expect this to improve in future generations of the system.

Yes, you could pair this lens with a body like the Panasonic GH7 for stronger video specifications, but in doing so you would lose one of the biggest advantages of this system: Sync IS. And that is a major trade-off. While brands like Sony, Nikon, and Canon advertise impressive stabilization figures on paper, in real-world handheld use the OM SYSTEM combination of in-body and lens stabilization is, in my experience, in a completely different league. It is noticeably more stable and confidence-inspiring than anything else I have personally tested so far.

That is exactly why, for me, switching systems just for video is not a realistic option at this point.

At the same time, OM System clearly has a golden opportunity here. Professional-grade 4K video at higher frame rates (such as 120p) is becoming increasingly important in today’s wildlife photography and videography world, and this lens absolutely deserves a body that can fully match its optical and handling capabilities in motion work.

I would love to come back to this section in the future and completely rewrite it—ideally when the OM SYSTEM OM-1 Mark III arrives with the kind of video performance that this lens truly deserves.

Conclusion: Versatile, Professional, and Packed with Potential

The M.Zuiko 150–400mm f/4.5 TC1.25x IS PRO is an extraordinary lens with a level of versatility that is genuinely hard to match. For still photography, it is nothing short of a dream—delivering outstanding image quality, exceptional reach, and handling that feels refined and purpose-built for demanding field work.

For wildlife photographers especially, this lens has all the makings of a true “crown jewel” in a kit. It combines portability, reach, and precision in a way that makes long days in the field not only manageable, but genuinely enjoyable. The balance, stabilization, and optical performance come together to create a tool that feels deeply professional and highly capable in almost any stills scenario.

After testing a large number of telephoto lenses across different mounts over the years, this is one of the very few lenses that has consistently stayed in my mind. It has become a kind of benchmark—almost a “halo lens” in how it sets the standard for what a modern super-telephoto zoom should feel and perform like.

It’s worth clarifying that I did not simply continue with a review copy—I later decided to purchase a brand new, retail unit for myself. That decision alone reflects how strongly this lens resonated with me in real-world use.

If you're a wildlife photographer, this lens can easily become the centerpiece of your kit. It offers a rare combination of portability, reach, and precision. A truly professional tool, and for me personally, already a genuinely legendary piece of glass.