Unfortunately for smaller sensors, easy-to-get lens resolution in lp/mm is largely independent of lens format. My 28-200mm (which is surprisingly sharp, although it has other optical issues) is delivering about 20MP of scene resolution on FF, which means about 8.5MP on APS-C. However, A FF sensor is nearly 4X the area of an MFT sensor, so my 28-200mm would only project about 5MP of resolution on an MFT sensor. Excellent MFT lenses tend to come in at around 6-7MP; only one that DxO tested reached 16MP (on a 20MP sensor). Olympus uses their “splash proof" label for the 12-40mm, indicating resistance to dust, water, and cold. The lens is a bit heavier than the similar Panasonic 12-35mm f/2.8, touching the scale 62 grams heavier at 382g (that’s 13.5 ounces in US-speak). The Olympus 12-40mm is sharp from 12mm all the way through to 40mm even wide open at f/2.8. At 12mm the corner performance is slightly softer than the centre but still way better than something like a Canon 17-40mm L. As mentioned the lens is bitingly sharp in the centre at f/2.8 and performance increases slightly when stopped down to f/4. 100% crop of above image

PAST BYLINES: Gear Patrol, PC Mag, Geek.com, Digital Photo Pro, Resource Magazine, Yahoo! News, Yahoo! Finance, IGN, PDN, and others. YMMV - If you can, I would recommend going to a camera store and trying both on your camera before purchasing.I have both lenses and a GH5. Optically the 12-40 is better at the frame edges at the wide settings at longer focusing distances. As a 'landscape' type shooter this would be the deal breaker. On the other hand the the 12-35 is smaller, lighter and has lens stabilisation. The 12-40 has better manual focus control which if you shoot video is an advantage. I also have the 12-60 2.8-4 and I'd say this is again better than the 12-35 at 12mm ( but not as good as the 12-40) but bigger and slower. In the end I mainly use the 12-40 as I can confidently shoot at 2.8 throughout the zoom range without worrying I need to stop down to get optimal sharpness. The 12-35 doesn't improve much when stopped down and the 12-60 needs to be at 5.6 at the longer end to achieve optimal performance at the frame edges. Sample variations may apply to my copy of the 12-60 but my 12-35 vs 12-40 results seem in line with most if not all tests I have seen over the years. Kowa Prominar 8.5mm f2.8: I saw this lens at the Photography Show in Birmingham 5 years ago but never got the chance to test a full production sample. The 17mm equivalent field of view is interesting but now that the smaller Laowa 9mm is out, I see little reason to get this one, especially considering the high price.

This lens delivers outstanding sharpness through much of the zoom range at maximum aperture and sports a robust, dust and splash proof build, all while remaining compact and lightweight. The excellent performance of this lens will certainly win it many fans, that's for sure. This is a pro-grade optic that's one of the "holy trinity" lenses, offering a fast, fixed f/2.8 aperture and full weather sealing. (Indeed, as noted, it offers the best weather sealing in the business.) Chromatic aberration is the lens' inability to focus on the sensor or film all colours of visible light at the same point. Severe chromatic aberration gives a noticeable fringing or a halo effect around sharp edges within the picture. It can be cured in software.Image Quality – Through the lens E-M1, 1/100, f/10, ISO 200 – M.Zuiko 12-40mm at 28mm GX8, 1/160, f/11, ISO 200 – Lumix 12-35mm at 33mm Focal Range When you're holding the camera up to your eye, with the lens cradled in your left hand, the balance with either is good, though the 12-35/2.8 feels slightly better as it is less front heavy. I think this is what most people talk about when they about balance.