OM System 40-150 mm f/4 Pro

The subject of this page is a compact and relatively affordable f/4 medium to long telephoto lens with an extended zoom ratio (3.75x). This lens is part of the OM System Pro lens series and was released in early 2022. It continues the pattern of Olympus/OM System of developing smaller and more affordable f/4 alternatives of remarkably good quality to its own f/2.8 range of Pro lenses.

OM System OM-1 with 40-150 mm f/4 Pro, stowed configuration.
OM System OM-1 with 40-150 mm f/4 Pro, in-use configuration.

Alternative choices

For several years, the Pro range of Olympus M.Zuiko lenses has included a 40-150 mm f/2.8 zoom of good quality. It is a good lens, albeit not quite as good as the best zooms in this lens range, or prime lenses like the 300 mm f/4 Pro. My main problem with this 40-150 f/2.8 zoom is that it is quite large, heavy and significantly expensive. While a reasonably high price is something I can live with, in return for top image quality, a weight of 880 g (with tripod shoe) is a bit high for me to add to my camera backpack.

The Olympus 150-400 mm Pro, with its built-in 1.25x focal length multiplier, is not a viable alternative for me because of its high weight, size and price. It is unquestionably the best among Olympus/OM System super-telephoto lenses, but I could not justify spending such a remarkably high price for a lens that most of the time would just sit at home because of its weight.

An Olympus 100-400 mm f/5-6.3 is available, but it is not a Pro lens, and optically not as good as the 300 mm (not even when the latter is equipped with a 1.4x focal length multiplier).

There is also a 4/3 (not Micro 4/3) legacy Olympus 50-200 mm f/2.8-3.5 SWD that performs well with its matching EC-14 4/3 1.4x focal length multiplier, or the Olympus Micro 4/3 1.4x focal length multiplier. This legacy lens provides a reasonably fast AF with recent high-end Olympus/OM System cameras (E-M1 II and higher, in particular the OM-1), albeit not as fast as native Micro 4/3 lenses. This is a relatively large and heavy lens, equipped with a solid tripod shoe.

There is even an affordable consumer-grade Olympus 40-150mm F4.0-5.6 R, which I have never tested. At 190 g, this is by far the lightest alternative, and surprisingly sharp especially at the center of the frame, with only a minor degradation of image quality at 150 mm FL. Compared to more modern lenses, AF speed and precision and the physical construction of the lens make it now primarily a suitable lens for beginners and occasional photographers. Note that the R version is the latest (fifth) release of this lens model. Earlier versions have more limited AF capabilities.

For a while, years ago, I used the Panasonic 100-300 mm consumer-level zoom, rarely with good results. Optically, it is not too bad, but its AF performance is very basic.

A few years ago, Olympus introduced a 12-100 mm f/4 Pro, with an extreme 8.3x zoom ratio. The 12-100 may be a good choice when you can carry only one lens, but my feeling is that this lens is a bit too much of a compromise between a wide zoom range and a good image quality. This lens would also completely overlap the focal range of my 12-40 f/2.8 Pro, which is a better lens. The 40-150 f/4 Pro provides a significantly longer maximum focal length than the 12-100 f/4 Pro, with an image quality worthier of the Pro denomination.

The scalloped lens shade of the 12-100 f/4 Pro is designed to prevent vignetting at the 12 mm focal length, so it cannot be very effective in preventing off-axis light from reaching the front element of the lens. The conical lens shade of the 40-150 f/4 Pro, on the other hand, provides a far better protection against flare.

My choice

I can live with the almost 1.5 kg weight of the 300 mm f/4 Pro, because it is the lightest top-quality alternative of this focal length among the Olympus/OM System lenses. However, this lens is at the high end of the weight range I can tolerate at present. In the past I have been toting around a Tamron 300 mm f/2.8 on a Nikon D70S, and even used it hand-held on birds in flight with some success, in spite of its slow AF and lack of in-camera and in-lens IS. Its 3 Kg weight, however, never made me happy. I own other large and heavy lenses up to 600 mm FL, but carry them in the field only if I have a really good reason.

I am no longer willing to carry a camera backpack weighing more than 6-7 kg on a walk in the field, and try as much as possible to stay well below 5 kg. Therefore, after purchasing the 300 mm f/4 Pro I passed up on the 40-150 mm f/2.8 Pro, kept waiting for something lighter that would not compromise on image quality, and used my feet as much as possible to get around the large gap in focal lengths of my lens kit between 40 and 300 mm. I finally felt that the 40-150 f/4 Pro was the best solution to fill this gap without straining my back and without compromising on image quality. I do not feel that the f/4 lens speed is a significant handicap, if paired with a modern top-of-the-line camera like the OM-1. My decision was further helped by a 2,000 SEK cashback offer from OM System Sweden.

Since my purchase of this lens, I used it on multiple occasions for types of photography I had not explicitly considered when making my lens choice. For example, I found it handy for product photography in the studio, where a telephoto focal length between 40 and 100 mm is handy in situations like the following figure. I shot this picture with the 60 mm macro, but a moderately higher focal length would have helped in further reducing the perspective rendering of the subject. Note how the two lenses seem to diverge away from each other in their upper portions, slightly but still noticeably. This perspective effect decreases with increasing focal length. It could be eliminated with a shift lens, but completely removing it may sometimes result in a slightly "unnatural" perspective rendering.

OM System 40-150 mm f/4 Pro (left, stowed) and Olympus 12-40 mm f/2.8 Pro (right).

At 382 g, the 40-150 f/4 is less than half the weight of its f/2.8 counterpart (880 g with tripod collar), and in stowed configuration not much bigger than the 12-40 mm f/2.8 (9.9 versus 8.7 cm from filter mount to mounting flange). The weight of the 40-150 f/4 and 12-40 f/2.8 happens to be exactly the same.

In the above figure, the 40-150 is stowed, and the 12-40 is zoomed to about 17 mm FL, which results in the shortest physical length of this lens (the lens barrel extends at longer, as well as shorter, FLs).

Characteristics of the 40-150 mm f/4 Pro

In spite of belonging in the Pro lens series, the design of the 40-150 f/4 is not without compromises:

  • This lens lacks an L-Fn button.

I do not use this customizable button. Among various reasons, it could be confusing because some of my lenses have this button, while others do not (e.g. the 60 mm and 30 mm macro lenses). Other photographers may have different opinions on the usefulness of this button.

  • This lens lacks a clutch on its focus ring to switch between manual focus and autofocus. You need to switch between autofocus and manual focus in the camera menu or SCP, or to configure a custom control for this function.

A focus ring clutch to switch between MF and AF is present on almost all Olympus/OM System Pro lenses including the 12-100 mm f/4, and even on some non‑Pro lenses like the 12 mm f/2 and 17 mm f/1.8. It is not completely clear to me how to frame OM System's decision to leave out this feature from the 40-150 f/4 Pro, although the main commercial result (reducing the complexity and cost of the lens) is obvious enough.

I guess perhaps leaving out the L‑Fn button alone did not save enough money on production costs, or perhaps it is a way for OM System to test the waters and see whether a "simplified" Pro lens still sells well enough. After all, this lens is clearly intended as a lighter and smaller alternative to the 40-150 f/2.8, and it would not be a wise marketing decision to include all bells and whistles and be forced to sell the f/4 lens at almost the same price as the f/2.8 lens.

The lack of a focus clutch does change the way a photographer works with this lens. On the OM‑1 with the 40-150 f/4, you can set the camera to SAF+MF or CAF+MF, half-press the shutter button to perform AF and keep this button half-pressed, then manually turn the focus ring to the desired focus before tripping the shutter. In any of the AF modes, you can press the AF‑On button to force an AF operation (unless you re-programmed it to work as a custom button).

You can disable AF from performing when half-pressing the shutter with the menu setting AF → AF 1 → AF by half-pressing (SHUTTER). You can even choose whether to disable only SAF, only CAF, or both. Once AF on shutter half-press is disabled, you must use the AF‑On button whenever you want to AF. In most cases I prefer to AF with shutter half-press, but in some situations, disabling AF on half-press (as opposed to setting the camera to MF) allows the photographer to both use the focus ring for MF and press AF-On when AF is necessary.

Also note:
- Pressing AF‑On performs an SAF operation, regardless of whether the camera is set to SAF, SAF+MF, CAF, or CAF+MF.
- If you set the camera to MF, the AF‑On button has no effect and you are stuck in MF.
- You must keep the AF‑On button pressed until AF is achieved. Releasing the button while the focus is still hunting instantly stops the AF attempt.

  • This lens lacks a tripod collar.

The lens seems to be lightweight enough not to place a dangerous amount of stress on the lens mount, but a camera with this lens mounted on a tripod head via a camera plate is decidedly front-heavy. This lens seems to be designed primarily for hand-held operation, so if you plan to use it mostly on a tripod, you may be better served by the 40-150 f/2.8 Pro.

  • This lens cannot use a focal length multiplier.

It does not matter much to me, since the 300 mm f/4 gives me far better results than a 150 mm with 2x focal length multiplier, but it may matter to other photographers. In practical use, it also does not matter much to me having a "hole" in focal lengths between 150 and 300 mm. I gladly give up this range of focal lengths in return for a much lighter camera backpack (and a heavier wallet).

The 40-150 f/2.8 does accept a focal length multiplier (either 1.4x or 2x), but on this zoom lens either focal length multiplier results in a larger deterioration of image quality than on prime telephoto lenses of good quality, like the 300 mm f/4.

  • There is no in-lens image stabilization, and consequently no IS slider switch on the lens barrel.

The 12-100 mm f/4 Pro does have in-lens IS, so the latter lens is a better choice if you need this feature. However, in-camera IS alone, with a recent E-M1 II, E-M1 III, E-M1X or OM-1, is already good enough with a focal length up to 150 mm. Combined in-lens and in-camera IS, in my experience, has noticeable effects only at 300 mm or higher FL.

  • The lens barrel has a stowed configuration, 25 mm shorter than when the lens is in use. The zoom ring is used to switch between the two configurations, and has a mechanical detent at the 40 mm focal length setting.

Virtually all current and recent Micro 4/3 camera models should display a message on the LCD screen and refuse to work when the lens is stowed, so you cannot by accident shoot with the lens in stowed configuration. This is a legacy capability dating from some of the very first Micro 4/3 consumer-level zooms, which also had a stowed configuration. This feature from the early Micro 4/3 days may explain why the camera only displays a white unformatted text message on black background, not unlike an MS-DOS screen, instead of a graphically more satisfying pop-up and a warning icon.

The physical extension of the lens front, just like the zooming extension of the 7-14 f/2.8 Pro and 12-40 f/2.8 Pro, potentially lets humidity and dust enter the lens, weather sealing notwithstanding. Since external air is drawn into the spaces among the lens elements when the front of the lens barrel extends, this air will unavoidably carry humidity and fine dust into the lens. On the other hand, the zoom action is internal, without changes in lens barrel length. Thus, zooming causes no air pumping into and out of the lens barrel.

To reduce the risk of condensation on or inside your lenses (which may invite the growth of molds), a good habit is leaving your lenses in the camera backpack until they have cooled down or (especially) warmed up to ambient temperature.

If you form a habit of storing the 40-150 f/4 in its in-use configuration in your camera bag, instead of collapsing it to its stowed configuration, the risk of internal contamination is reduced. If you store the lens horizontally in your camera bag, it will be less likely to collapse into its stowed configuration under the effects of gravity and bag shaking. This wastes only a minor amount of space in your camera backpack, since this lens is only moderately shorter when stowed. Other lenses (e.g. the 40-150mm f/4.0-5.6 R) almost double in length when fully extended and zoomed.

The stowing, zoom and focus mechanisms of the 40-150 f/4 do not creep under the effect of gravity when the lens is pointed downward, so it can safely be used on a repro stand.

  • Some of the extreme capabilities of the OM-1, like very fast sequence shooting, are not available with this lens. CAF performance of the 40-150 f/4 is fast (some photographers use this lens for birds in flight), but not on par with the best Pro lenses. On the OM-1 in subject tracking mode, with the right combination of settings, in my experience lenses like the 300 mm f/4 produce a 95% or better keeper rate on birds in flight, while the 40-150 f/4 produces a somewhat lower keeper rate.

Lens shade

The lens comes with a reversible plastic lens shade (LH-66E). This lens shade has a small, flush button that must be pressed to unlock its bayonet. The locking button reduces the risk that the lens shade will accidentally fall off while the camera is carried on a neck strap in the field, but requires one additional manual operation every time the lens shade is reversed. When the lens shade is reversed, enough of the zoom ring remains accessible to easily switch between lens configurations, but the focus ring is completely covered by the reversed lens shade.

Zoom ring rotation

The rotation of the zoom ring between 40 and 150 mm is limited to less than one-quarter of a turn. The rotation is smooth, albeit not as smooth as in other Pro lenses. Also, the front of the lens slightly wiggles (by a fraction of a mm) when extended. The consumer-grade standard zooms that came with my Nikon D-200 and D-300 DSLRs a decade ago were far worse in this respect.

Maximum close-up magnification

At 40 mm FL, the 40-150 f/4 focuses up to a 0.07x magnification (i.e. a field of view of 24.7 by 18.6 cm), and at 150 mm 0.21x (8.2 by 6.2 cm). This does not reach the macro range, but may be sufficient for close-ups of subjects like plants and large flowers, and is more than enough for portraits. The maximum magnification is obtained with the lens zoomed to 150 mm, but the working distance at closest focus increases with increasing focal length. In other words, as a habit you should zoom to 150 mm when shooting close-ups, but in crowded settings (e.g. flowers partly hidden among tall grass or bushes) it may be desirable to use a shorter focal length, if compatible with the magnification you are aiming for.

The 40-150 mm f/2.8 reaches the same 0.21x magnification as its more recent f/4 counterpart. Evidently, the OM System engineers designed the f/4 lens to be as compatible as possible with its f/2.8 "big brother". This is a significant break with the "traditional" marketing strategy of lens makers of offering one professional lens model with all the possible bells and whistles, and a smaller and cheaper, amateur-oriented model of comparable focal length but with clearly lesser capabilities in most respects. The 40-150 mm f/4 indeed does away with some capabilities, in addition to the lower lens speed, but not at the expense of image quality and close-up magnification, which are the two things that matter most in practical use.

Optical design

The optical design uses 15 elements in 9 groups, with plenty of special elements (2 ED, 1 super ED, 1 HR, 2 aspherical). The diaphragm has 7 blades. The front filter mount has a 62 MA thread, like the Olympus 12-40 mm Pro.


The lens and its front and rear caps are branded OM System.

Image quality

All following test images were shot with the OM System OM-1 handheld at ISO 200 with IS and silent shutter, on a bleak day at the end of November without much light. Except for downscaling or cropping, the images are Fine JPGs quality straight out of the camera.

40-150 f/4 Pro at 40 mm FL and f/4, reduced image.
40-150 f/4 Pro at 40 mm FL and f/4, 1:1 center crop.
12-40 f/2.8 Pro at 40 mm FL and f/4, 1:1 center crop for comparison.
40-150 f/4 Pro at 150 mm FL and f/4, reduced image.
40-150 f/4 Pro at 150 mm FL and f/4, 1:1 center crop.

The two first images in the above series show the 40-150 f/4 at 40 mm FL and f/4 (reduced image and 1;1 crop, respectively). The third image, for comparison, shows a 1:1 crop from the 12-40 mm f/2.8 at 40 mm and f/4. I cannot see any substantial difference in resolution, contrast or color, but the image from the 40-150 f/4 seems slightly sharper. At 40 mm FL, a potential advantage of using the 40-150 mm instead of the 12-40 f/2.8 is the better protection against off-axis light provided by the lens shade of the former.

The 12-40 mm Pro at 40 mm turns out to have a lower actual focal length than the 40-150 mm Pro. Probably, the 12-40 mm only reaches an actual focal length of about 38 mm. This leaves a slight gap of focal lengths between the two lenses.

The last two images in the above series show the 40-150 at 150 mm and f/4. A noticeable difference between the focal lengths of 40 and 150 mm is that the color is colder at the latter FL, compared with the warmer tones of the same subject at 40 mm. Both lenses at 40 mm produce the same warmer tones.

In order to further test whether and why the color temperature changes while zooming, I repeated the tests with the 40-150 on a different subject at 40 and 150 mm (below).

Second test of 40-150 f/4 Pro at 40 mm FL and f/4, reduced image.
Second test of 40-150 f/4 Pro at 40 mm FL and f/4, 1:1 center crop.
Second test of 40-150 f/4 Pro at 150 mm FL and f/4, reduced image.
Second test of 40-150 f/4 Pro at 150 mm FL and f/4, 1:1 crop.

Also in this case, there is a modest change in both WB and brightness. The explanation is simple: All above tests were performed in auto WB and auto exposure, and the WB and brightness changes are due to the fact that the test pictures at different focal lengths contain different proportions of water, boathouse and sky, which naturally affect both WB and exposure.

Changes in exposure while zooming are often not so noticeable, and in many cases they are actually a good thing (to avoid under- or overexposure of details). Changes in WB and color rendering may affect the final results in less favorable ways. If you need to avoid either type of changes (e.g. when zooming while filming, or when pictures at different zoom settings must be published side-by-side), you should shoot at a fixed WB, and often also in manual exposure.

Since no current Olympus/OM System camera has an external WB sensor, these cameras compute both auto exposure and auto WB from live view data or recorded images. Some legacy DSLRs (e.g. the Olympus E-1 and E-3, Nikon D2H) do have an external WB sensor that complements the auto WB adjustments computed from an internal sensor pointed to the ground-glass screen in the viewfinder, or from live view, or from recorded images. Such an external sensor was useful in cameras lacking live view capabilities, but has generally been abandoned in more modern cameras because of its low reliability as well as functional limitations.

A few in-depth tests of this lens have been published, for example on Amateur Photographer. At least one reviewer rated it as "insanely sharp". SAF is fast, but this lens does not equal the CAF performance of the 40-150 mm f/2.8. Image quality is excellent already at f/4, and there is no need to stop down in order to improve the image sharpness. Image quality is good across the whole frame and, unlike in many consumer-grade zooms, does not significantly degrade at the highest focal lengths.

The nominal aperture of the 40-150 ranges from f/4 to f/22. Like in all Micro 4/3 lenses, image sharpness is best up to f/8, or f/11 with a minor degradation caused by diffraction. Higher apertures should be avoided, unless a higher DOF is more important than a high sharpness. This may be the case in small catalog images, e.g. to be published on a web shop.

The f/4 lens speed means that DOF is moderately higher fully open, compared to an f/2.8 lens fully open. This is rarely a problem with a telephoto lens, which tends to produce a shallow perceived DOF in any case (as a result of objects in a distant background being rendered at a larger relative size than with a wideangle lens). The moderately shallower DOF of an f/2.8 lens, as well as the shorter exposure time when shooting in ambient light, can be advantageous in some cases, but in my experience these advantages are rarely worth carrying a heavier, larger and more expensive lens on my back in the field.


The OM System 40-150 mm f/4 Pro is an excellent telephoto zoom in a reasonably lightweight and small package. With respect to its f/2.8 Pro counterpart, it sacrifices one stop of lens speed, some CAF performance, some sequence shooting speed, and a few features like L-Fn button, in-lens IS and tripod shoe. The 40-150 f/4 Pro is very sharp fully open and at all focal lengths.