Previously, the only wide to medium zoom lens for m43 we had was the Olympus 12-50/3.5-6.3. While a decent, versatile kit lens, it does not favor shooting in low lighting conditions based on its variable and comparatively slow aperture range. Subscribe to see EXIF info for this image (if available) 1/1600, f/6.3, ISO 200 @ 12mm While we do have primes that pretty much cover the range we are looking at with the 12-40/2.8, having a fast zoom is great for those times when you cannot or do not want to change lenses. Subscribe to see EXIF info for this image (if available) 1/500, f/4, ISO 200 @ 26mm Image Quality Like the 40-150/2.8 PRO, I can't really find a lot of fault with the IQ at any aperture or any focal length. You have your normal IQ drop off at f/11 and above due to diffraction, but beyond that, I find it stellar. There is some noticeable barrel distortion at 12mm, but nothing that a run through Lightroom and the lens correction module can't handle. The bokeh is pleasing when you are focusing up close. Based on the sensor size we are working with anything focused on at further distances gives you lots of in focus areas. The bokeh isn't bad, but your not going to get a lot out of focus either. From the sample images, shot wide open and in the challenging conditions, this lens is fantastic in the IQ department. Subscribe to see EXIF info for this image (if available) 1/320, f/4, ISO 200 @ 15mm Handling This thing is small when you think about what you are getting in the exposure department. A 12-40 f/2.8 focal length, You get a 24-80 field of view. The zoom ring is smooth and dampened and feels every bit a pro grade lens as the name Olympus gave it implies. The focus ring is smooth and moves from one point to the other very quickly. I like the AF/MF clutch as well for those times when you want to quickly switch over to MF. No menu diving and you get the added bonus of snap focusing. Subscribe to see EXIF info for this image (if available) 1/2500, f/4, ISO 200 @ 24mm Weight Compared to the 12-50mm lens, this one is on the heavy side. Compared to an APS-C or 135 equivalent f/2.8 lens, it is down right small and light. hand holding this lens on an EM1 or EM5 with after market grip is easy. Subscribe to see EXIF info for this image (if available) 1/2000, f/2.8, ISO 200 @ 40mm Auto Focus Speed Single point AF is lightning fast in all but the poorest of light. Even in poor light, though it is slow, but tends to hit the mark. There is some hunting, but only when the lighting is so dark it is hard to see your target with the naked eye. At that point any camera system is going to struggle Continuous AF works great! I've not had an opportunity to see what the lens did pre firmware 3.0 on the EM1, but I've never heard of any complaints from anyone about it. I might take some time and see how it performs on the EM5 as a comparison. Close focusing is also another plus of this lens. It is not macro level, but like the 40-150/2.8, you can get right up close, I believe that you can get 4cm from the front element!! Subscribe to see EXIF info for this image (if available) 1/200, f/4, ISO 200 @ 31mm Lens Hood The hood is reversible and has a positive locking mechanism. There are 2 buttons on the hood that must be pressed before the hood can be twisted for removal. You'll not be losing this one accidentally. It is kind of shallow, but can provide some front element protection and shading. It is in no way as deep as the one that comes with the 40-150/2.8 Subscribe to see EXIF info for this image (if available) 1/80, f/4, ISO 640 @ 40mm Conclusion So far, just from this one day of shooting and seeing the results, I am sold on the capability of this lens. It is sharp, handles well, everything is in a great place and the AF performance is top notch. I'm not sure if Olympus could have made a better wide to medium telephoto zoom lens. As much of a winner as this lens is, it is expensive when compared to other zooms in the same focal range. However, this is a pro grade lens, while the others are not (except the Panasonic 12-35/2.8, which is a great lens in its own right).