The ribbed zoom and fly-by-wire focus rings are smooth with just the right amount of torque, and the focal lengths are clearly and accurately marked. Richard "If I take an image on a 150mm F4 lens on micro four thirds, and one at 300mm F8 on full frame for the same exposure time, then both sensors will be exposed to the same number of photons."

Those looking for a professional specified standard lens for their Micro Four Thirds camera are now spoilt for choice with offerings from Panasonic, and this lens from Olympus. Personally speaking, I find it more useful to have the constant 2.8 aperture since it allows me to keep the ISO value down even in poor light. However, I can appreciate that others might prefer the extra reach for everyday photography, casual portraits or travel. This is especially true if you mostly work in favourable light conditions. G85, 1/100, f/4, ISO 200If you are trying to decide between this lens and the Panasonic 12-35mm (mark i or mark II) then it really comes down to a few factors as optically they are very similar. The Olympus is better at the wide end and offers a little more range at the long end. However the Panasonic is slightly sharper at 35m than the Olympus is at 40mm. Stopping down to ƒ/4 to ƒ/5.6, you have the "sweet spot" of apertures for critical sharpness at all focal lengths. Corner to corner, the lens displays fantastically sharp images in this range of apertures. We did see some diffraction softness come into play at the smaller apertures such as ƒ/16-ƒ/22, but overall it wasn't very severe. The optical formula is unchanged, comprising 14 elements in nine groups, including one Extra-low Dispersion Aspherical (EDA) element, two aspherical elements, one Dual Super Aspherical (DSA) element, two Extra-low Dispersion (ED) element and one High-Definition (HD) element. It features a minimum focusing distance of 20cm (7.9”) and measures 67mm (2.6”) diameter, 84mm (3.3”) long and weighs 382g (13.5oz) without the lens caps or hood.

Olympus has been developing its PRO series of lenses since late 2013, the year in which the original OM-D E-M1 was released. The first lens in the series was the M.Zuiko 12-40mm f/2.8 PRO which rapidly became a favourite amongst many advanced amateurs and professionals, ourselves included. It was later joined by five more lenses, the latest of which is the M.Zuiko 12-100mm f/4 PRO, whose announcement coincided with the release of the E-M1 II. Pair the lens with the Dual I.S. (combined optical and sensor stabilisation) of select Lumix cameras, such as the G85, GX85 or GH5, and you can achieve good results down to 1.6 seconds at 12mm or 1 second at 60mm. G85, 1.6s, f/5, ISO 200 – Pana-Leica at 12mm G85, 1 second, f/4, ISO 200 – Pana-Leica at 60mm The Olympus OM-D E-M1 used for this test is a great match for the lens, offering good balance, fast auto focus, and full environmental seals. The M.ZUIKO Digital 12-40mm f/2.8 Pro lens itself is very well built, fully living up to the PRO designation that Olympus have given it. The 12-60mm has one important advantage over the 12-40mm, and that is its built-in optical stabilisation. When mounted on an Olympus or non-stabilised Panasonic Lumix body, it is possible to take sharp shots down to shutter speeds as slow as 1 second at 12mm or 0.4 seconds at 60mm – if you haven’t been drinking too much coffee, that is! E-M1 (OIS priority), 1 second, f/3.2, ISO 200 – Pana-Leica at 12mm E-M1 (OIS priority), 0.4s, f/4, ISO 200 – Pana-Leica at 60mmYou can get really close with this lens. I think it's a very nice option to have and I can imagine that many photographers don't need an extra macro lens. This Olympus 12-40mm might very well be the only lens many people ever need. Especially when combined with the very efficient Olympus in body stabilization. It's a do it all kind of lens. And it does it well too. Optical Quality – Through the lens E-M1, 1/500, f/11, ISO 200 – 12-40mm Pro E-M1 II, 1/100, f/5.6, ISO 200 – 12-100mm Pro aspherical element, 1 dual-sided aspherical element, 2 ED glass elements, 2 HR glass elements, 1 EDA glass element, 1 HD glass element

The Olympus 12-40mm ƒ/2.8 Zuiko PRO represents a new category for Micro Four Thirds lenses, and as such, there arenot many direct competitors that can be seen as alternatives. Nevertheless, there are options out there. Three years ago, we bought the Olympus M.Zuiko 12-40mm f/2.8 for our personal use, so the question I’ve been asking myself throughout our testing period is: would I replace the Olympus lens with the Pana-Leica 12-60mm f/2.8-4.0? Further out is the smaller, metal-ribbed focus ring, which is about half an inch wide. It rotates easier and smoother than the zoom ring. When you want manual focus, pull the ring toward you to engage manual focusing and reveal the focus distance scale. The focus ring will rotate indefinitely when using autofocus but will rotate about 90 degrees in manual focus with hard stops at either end.At 12mm sharpness is already outstanding across the frame, and there is only a slight improvement in clarity when stopped down one stop. This pattern is repeated at 18mm with excellent sharpness being achieved between maximum aperture and f/8.