… or is it?
OM System 100-400mm f5-6.3 II IS lens Review
This has been very difficult to write and has become a very long and drawn out affair and it shouldn’t have been.
I have, as regular visitors to the site may recall, been using the Panasonic Leica DG Vario-Elmar 100-400mm f4-6.3 lens for my wildlife photography since September 2018. I bought it because it was the only affordable quality long lens available in Micro Four Thirds at the time. Largely I have been very, very happy with it. The major nitpick I have is that although both Panasonic and Olympus/OM System are part of the Micro Four Thirds consortium and conform to certain protocols such as lens mounts, flash system standards, and autofocus compatibility some features are not cross brand compatible. Now when I got the lens I was primarily using a Panasonic Lumix G85 with which it mates up perfectly and an Olympus EM1 mk 1 which was close enough. But as I progressed with Olympus cameras some of the features such as Synch IS, autofocus while using Pro Capture, focus stacking and high resolution functions required complete compatibility and I was wanting to use them on a regular basis. When Olympus introduced the mk 1 version of the 100-400mm lens in 2020 it seemed weird as it wasn’t compatible with those features so I saw no need to change. So with the announcement in February 2025 OM System announced the OM System 100-400mm f5-6.3 II IS lens and that they had fixed some those issues I became very interested and bought it after watching and reading many, many positive reviews.
One of the things that has made this so difficult is because I keep making comparisons to the Panasonic 100-400mm mk I which I also own. In fact, it is probably more a comparison review than anything else, which is unfortunate as I wanted to make it a stand alone look at the OM System 100-400mm.
The Controversy
When the original Olympus 100-400mm came out a lot people jumped on the fact that it was simply a rebadged SIGMA 100-400MM F/5-6.3 DG DN OS Contemporary Lens. The criticism mainly centred on the fact that it was firstly a lens designed for full frame cameras rather than specifically for Micro Four Thirds which meant some how that it was too large and heavy and undermined the original m4/3 ethos of being small and light. The second complaint was that the original Sigma lens sells for around half the price of the Olympus/OM System version so, therefore, customers were being ripped off by Olympus/OM System. When the OM System 100-400mm f5-6.3 II IS lens was launched these same complaints were again raised. Well the truth is somewhat different.
While both lenses may have been built by Sigma (and there is no definitive proof that the Olympus/OM System lens has been) there are some key differences. While they share the same focal length, aperture range, and thermally stable composite body the filter size of the Sigma is 67mm compared to 72mm of the OM System lens. The Sigma lens has a lens construction comprising of 22 elements in 16 groups with four FLD elements and one SLD element. The OM System 100-400mm lens has 21 elements in 15 groups with four ED elements, two HR elements and two Super HR elements. The OM System lens diaphragm has 9 circular blades while the Sigma has 7. The OM System lens has IPX1-rated weather-sealing and there is no rating for the Sigma. The OM System lens’ front element has a ZERO Coating which is a form of fluorine coating that repels water and smears keeping it clean. The Sigma’s image stabilisation is four stops while the OM System’s is 5 on its own and it fully integrates with their cameras IBIS to give 7 stops of image stabilisation.
At this point I think it is fair to say that the OM System lens is not a simple case of badge engineering, there are too many differences. Now I’m not saying that OM System didn’t contract Sigma to build the lens using their existing SIGMA 100-400MM F/5-6.3 DG DN OS Contemporary Lens as a framework. What I am saying is that are sufficient differences in the specifications and they should be treated as entirely separate entities.
Vital Statistics
| Focal Length | 100-400mm (35mm equivalent 200-800mm) |
| Mount | Micro Four Thirds |
| Lens Construction | 21 elements in 15 groups with four ED elements, two HR elements and two Super HR elements |
| Lens Coating | ZERO Coating |
| Angle of View | 12° (wide) – 3.1° (tele) |
| Number of Diaphragm Blades | 9 rounded blades |
| Maximum Aperture | f/5.0 (wide) – f/6.3 (tele) |
| Minimum Aperture | F22 |
| Minimum Focusing Distance | 1.3m |
| Maximum Magnification Ratio | 0.09x (wide) – 0.29x (tele) |
| Filter Size | 72mm |
| Dimensions | 86.4mm ⌀ × 205.6mm h |
| Weight | 1,125g |
| Supplied Accessories | lens hood |
| Weatherproof | IPX1-rated weather-sealing – Dust-proof, Freeze-proof, Splash-proof |
| Lens Sync IS | 5-Axis |
The OM System 100-400mm is not part of the top tier PRO line of m.Zuiko lenses, but rather one of their consumer grade ones. Consequently it does not have the metal body nor MF Clutch / Snapshot Ring but rather a nondescript composite body that is strictly utilitarian. The zoom is of the external variety in that the lens barrel extends as you zoom through the focal range, but the focusing is internal and the front element does not rotate as the lens focuses. The mechanism feels sturdy with no hint of any flex or wobble. At the mount end there is a chromium plated brass mount which is surrounded by an “o” ring which provides a seal between the lens and camera body. Be aware that OM Systems OM1 mk i & ii, OM3 and OM5 mk i & ii have an IPX rating of 53 which means that they are protected against low pressure water streams from any angle and while not completely dust proof any ingress that does occur will not interfere with the operation of the camera. The lens is IPX1 rated which means that there is no information available about resistance to dust ingress and it is resistant to vertically dripping water equivalent to 1 mm rainfall per minute. So the camera body has more resistance than the lens.
The lens is quite a chunky beast and it also has considerable weight. It is when you compare it to the PanaLeica 100-400mm that this becomes really apparent. The PanaLeica is 34.1 mm shorter, 3mm in diameter smaller and 140g lighter while having a much more premium metal body that just exudes class. In comparison the OM System lens comes off as feeling lumpen and a little tacky.
When it comes to controls both lenses are pretty the same. A zoom ring, focus ring, zoom lock and switches for the AF function, focus limiter and image stabilisation. The OM System lens scores well here as the PanaLeica is plagued with an incredibly stiff zoom ring, but overall the PanaLeica gives to my mind a much better user experience.
On launch there was a lot of fanfare about the new tripod collar. Yes it’s different from the one on the original version but you’d hardly call it innovative. I see it as a solution to a problem that never existed. I’m amazed that so many of the internet reviews went on and on about this giving scant attention to things like autofocus and optical performance. If you want to see a truly innovative approach to tripod collar design look at how Panasonic implemented theirs on the PanaLeica 100-400mm.
The OM System 100-400 includes a bayonet type lens hood in the box while the PanaLeica has a a two piece lens hood (a mini hood permanently attached to the body of the lens and a separate extension that attaches to it) and also throws in a lens pouch. To be honest I’ve never used it, but, it’s nice they’ve taken the effort to include it.
Performance
Sharpness
At 100mm wide open at f5 the performance is even across the frame – a little soft and lacking contrast. At f5.6 the contrast improves a little but the sharpness remains the same. At f8 there is no improvement. At f11 the lens reaches it’s best performance and at f16 softness in the form of diffraction re-appears.
Best results from the lens came at 200mm, with the best results at f11.
At 400mm wide open at f6.3 at the centre of the image the lens is soft and lacking contrast and the corners match this. The results follow the progress of the shorter end with best performance at f11.
This is very disappointing as the lens is not capable of resolving fine feather detail wide open unless you stop down to f11 which makes the lens really unsuitable for low light or birds in flight as you’ll have to use very high ISOs to get high shutter speeds and that kills image quality.
Flare resistence
Over all flare resistance is very good – the lens coatings are working well to minimise veiling flare. There is some ghosting present – polygonal shapes and light streaks – and it starts to become intrusive at f8. The diffraction spikes are not pretty at all, but then you don’t buy a lens like this for the diffraction spikes.
Chromatic aberration
Transverse or lateral chromatic aberration is present, but it is very, very slight and you really have to pixel peep to find it or turn off the lens profile in your image editing software.
Axial chromatic aberration, also known as longitudinal chromatic aberration is virtually nonexistent, but that is to be expected with such a small maximum aperture.
Autofocus
If you think this has been a pretty damming review so far well all I can say is brace yourself as we haven’t dealt with the lens’s major short comings. Now before any of you complain about me having a faulty camera I tested the lens on an Olympus EM1, two different EM 1 mk 2s, and an EM 1x and got the same result. The lens and the cameras all had the latest firmware installed.
At best using continuous autofocus on a slow moving target – me walking – I got 56% of the images in focus. Putting a stuffed toy bird on a slider and having it move back and forth 40% of the photos were in focus. At this point I contacted OM Systems Australia and sent the lens into them for recalibration. On getting it back the performance was actually worse with only 20% of photos in focus. The problem is that it seems to take ages for the lens to acquire focus and if it does it will momentarily grab focus for a couple of frames before drifting off again. The number of times where I’ve had a bird sitting just 5-10m away from me with a clear background and the camera and lens refuses to lock on to it. Frustration just doesn’t begin to express what I feel when that happens. Switch the lens over to the PanaLeica and there is no problem. Even the much cheaper OM System 75-300mm MKII lens performs better than the OM System 100-400 despite being a quarter of the price.
When shooting video the situation is worse. It struggles to find focus and then will inexplicably drift off.
At the time of writing the lens is with OM System Australia for “evaluation”.
Image Stabilisation
This is an area where the 100-400 excels. OM System claims that the optical stabilisation of the lens combines with the the in body image stabilisation of the camera body to give 5 axis stabilisation of 7 stops. Back in the days of yore when 35mm film SLRs were the norm there was the old adage of the minimum shutter speed you can hold is the reciprocal of the the focal length. So with the micro four thirds crop factor a focal length of 400mm is the full frame equivalent of 800mm and it would need a shutter speed of 1/800 sec to avoid camera shake. Now seven stops would take us down to a shutter speed of 1/6 sec and with my shake hands I could only get 1/13 or 6 stops and get a sharp image. Pretty impressive by anyone’s standards. The practical application of this is that for taking photos of birds I don’t often go below 1/500 sec so it seems overkill, but for video that is another matter entirely and it makes it possible to shoot handheld with this lens.
Minimum Focusing and Maximum Magnification Ratio
Conclusion
Thomas Eisl in his review:
“When working with the 100 to 400 Mark II in practice, one of the first things you will notice is the exceptional focusing performance…It is therefore highly suitable not just for wildlife photography, but also for professional wildlife film making.”
“The exceptional autofocus performance stems from full compatibility with the latest OM system autofocus technologies. This lens is swift enough for the speediest of all subjects and is definitely on par with OM system pro lenses in that regard.”
“Now to conclude the optical performance analysis, it is fair to state that the 100 to 400 M Ii delivers where it matters most and compromises, if existent at all, are very minimal. Overall, a lens capable of professional results, even under demanding conditions. No wonder that this is my most used super telephoto lens at the moment.”
“The OMS 100 to 400 F5 to F6.3 M II stands as a highly capable super telephoto zoom. Its robust yet portable construction, impressive image stabilization and swift autofocus cement its position as a reliable tool for demanding applications like sports and wildlife.”
“This lens delivers a performance that feels almost too good to be true both on paper and in the field.”
Mike Lane states that there is very little difference between the $2200 OM System 100-400mm f5-6.3 II IS lens and the $12,000 150-400mm F4.5 TC1.25X IS PRO.
Espen Helland says “I’m really impressed with the sharpness of the new lens, my photos at 400mm are tack sharp.” and “Though the 100-400mm chases with autofocus a little bit more than my 150-400mm f/4.5 it still performs really well.”
So with these glowing reviews I reflect on my own experience with supposedly the same lens. As it stands, I think that based upon my experience that the OM System 100-400 mk ii is actually unsuited to wildlife photography. The autofocus is incredibly poor and will just frustrate the hell out of you – well it certainly did me. When it does find focus at 400mm, which is where most bird photographers will use it, it is incapable of resolving any fine feather detail. Now it maybe that I just have higher standards than the other reviewers, but I highly doubt that. It maybe that camera and lens manufacturers make sure they send out perfect examples for review. Possible. I know that if I were sending out a product for critical evaluation I would definitely send the best of the best. More likely I just got a lemon. Now if that’s the case then why aren’t OM System looking to rectify the problem. At the time of writing their official line is no refund, no replacement and we’ll begrudgingly look at the lens , but won’t necessarily do anything. That leaves a very sour taste in my mouth and makes me want to change brand. Now OM System doesn’t have a very large market share, they are really struggling to break even (at the end of 2024 they were ¥1.2 billion or $120,000,000 AUD in the red) so alienating existing users seems like economic suicide.
Can I recommend the lens? In short no.
If you’re an Olympus/OM System camera user and not fussed about synch IS, the computational functions and the need for teleconverters then buy the PanaLeica 100-400 it is the much better lens in every way. If those functions and the use of teleconverters are important then I’d skip this lens and sell some body parts and get either the OM System 300mm or 150-400mm. Don’t waste your money on this lens.
paulamyes 
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