I found the 300mm f/4 to performed superbly in low light, a problem often encountered by wildlife photographers, because the f/4 maximum aperture is higher than you’ll usually find at 300mm for the M4/3 system. I found myself able to shoot well after sunset and still handhold my shots. At times, I was shooting at slow speeds between 1/60th and 1/100th and still catching crisp photos. The image stabilization system is definitely working hard. The stabilisation on the lens combined with the camera body stabilisation continues to amaze me to the point where I rarely take a tripod out with me now. I think it’s pretty clear what Nicholas is saying here. It’s not just the DOF that is changed, but also total light gathering capacity. In other words, if all else is equal (i.e. exactly the same subject and distance, light, etc.), a 600 f/4 lens on full-frame will gather much more light than a 300 f/4 on micro four thirds. This matters especially in the case of wildlife: in low-light scenarios, a 600 f/4 shot on full-frame will be much less noisy than a 300 f/4 shot on micro four thirds, where both shots have been equalized to the same viewing size. Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it. The teleconverter doubles the focal length of the master lens, which in the case of the 150-400mm results in an astonishing reach of 2000mm (working in tandem with the lens' integrated 1.25x teleconverter).

The Olympus 300mm f/4.0 IS PRO is admittedly an expensive lens. Does it’s performance make up for the high price tag? Sharpness Having used this lens for 2.5 years now, I can second what has been written so far. I would like to add the following positive aspects For good measure, I did a simple autofocus test with the OM-1 to see how long it took to focus from the minimum focusing distance to a distant wall. I did the same with the Olympus 100-400 f/5-6.3 and the Olympus 100-300 f/4-5.6. These are my results.

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However, keep in mind that crop factors also apply to aperture; so, using this lens is akin to using a 600mm f/8 on full-frame.’

Our primary interest in this lens is from the perspective of shooting birds, so the lens first real test was a Treecreeper close to our local canal. Additionally, when this lens is paired with the newer Olympus bodies like the OM-1, the lens and camera work superbly together with excellent image stabilization and autofocus. The stabilization is most effective when paired with Olympus bodies, where synchronized image stabilization will give you up to 6 stops stabilization. Wildlife photography simply became much easier with a modern lens/camera combo like this. Close Focusing Ability There is a minute improvement in sharpness between f/4.0 and f/5.6 which is really only noticeable in lab-like conditions. I was able to take full advantage of the f/4.0 maximum aperture without worrying about paying a price in sharpness.No, that’s not true. The aperture will be THE SAME. If you measure the exposure trough this lens wide open on any M4/3 camera, and then the same scene with any FF 300 or 600mm lens open to f/4 and mounted on any FF camera – with same ISO you’ll get the same exposure time as on Olympus. Aperture is a physical property of lens, not a sensor. F/4 lens will be always f/4, no matter how big is the sensor inside the camera you’ll mount it on: for example, if I mount my full frame 70-200/2.8 Pentax lens on K-1 II or my APS-C K-3 III – it always will be f/2.8 maximum aperture lens. As you can imagine, the ability to achieve such extraordinary reach made it much easier to capture shots of lions, elephants, cheetah and other animals that don't take kindly to people getting too close. This kind of no-nonsense functionality usually makes teleconverters a bit boring to write about. However, when it comes to Micro Four Thirds (MFT), teleconverters suddenly become a whole lot more exciting.

Thus, it makes sense to say that a 300 f/4 on micro four thirds is like a 600 f/8 on full-frame, when you are talking about equalized viewing size in terms of both DOF and noise/total light gathering! (Not light gathering per unit area) If 300mm is simply not enough reach, the Olympus MC-14 and Olympus MC-20 are both compatible with the Olympus 300mm f/4.0 IS PRO. These teleconverters multiply the focal length by a factor of 1.4 and 2 respectively. Of course the caveat, as with any teleconverter on any format, is a reduced maximum aperture of a given lens. A 2x converter results in a 2-stop reduction, meaning that the 40-150mm f/2.8 becomes an 80-300mm f/5.6, and so on. For the price difference between the two lenses, we would absolutely recommend the MC-20 –not only does it deliver super telephoto range for sports and wildlife shooting, it also doubles the magnification for super telephoto macro shooting. I've now had the 300mm F4 Pro for a little over 3 months. The main development has been that I've upgraded to the Olympus E-M1 MKII as the auto focus capability of the E-M5 MKII just wasn't up to birds in flight, which was something I was keen to have a go at.Theres obviously a lot more to think about with this combination. Im interested to see how its close focusing (down to 1.4 metres would you believe) works for dragonflies and other small subjects like lizards, and theres also still the question of how well the auto focus performs over time compared to equivalent DSLR combos. The only handling flaw I noticed in my time with this lens involves the focus ring. The ring rotates very smoothly, but the lens easily switches from autofocus to manual-only by sliding the focus ring into the manual position. On average it took the Olympus 300mm f/4.0 IS PRO 0.52 seconds to acquire focus. Interestingly, both the Olympus 100-400mm f/5-6.3 and the Olympus 100-300mm (a relatively old copy, though) took 0.80 seconds on average to acquire focus. In other words, the Olympus 300mm f/4.0 is about 50% faster than my copies of these other lenses. DC-G9 + OLYMPUS M.300mm f/4 @ 300mm, ISO 1000, 1/160, f/4.0 Use with Teleconverters The lens was so sharp, I even found moire on birds feathers, an issue I’d never encountered before! DC-G9 + OLYMPUS M.300mm f/4 @ 300mm, ISO 800, 1/500, f/4.0 Bokeh