We know already all the big advantages of using a so-called "Pro" lens. Better construction, larger controls and grip, better quality glasses, constant aperture (most of the time), all weather protection, etc. But "pro" lenses are also larger, heavier and... more expensive. Usually their variable focal length latitude is narrowed compare to the "amateur" counterparts.So it can be tricky to suggest or moreover to recommend such an exclusive product. And I am not a big fan of "bazooka" lenses that are intimidating the subject by their lack of discretion. The only add credibility you can expect from other people when using this type of lenses usually came from persons without real knowledge of photography (especially press credential personal).
So you can be rightly suspicious when I decide to bring you this specific and modest personal review about the Olympus M.Zuiko 12-40mm F/2.8 lens.
The Olympus M.Zuiko 12-40mm F\2.8 is in fact a big lens. It is true to say that it is a smaller lens compare to its equivalent in larger image actor format such as APS-C or 24X36mm so-called "full" frame format. Its focal length latitude offers a practical range starting with an interesting wide angle up to a modest telephoto setting. Its constant maximum aperture of F/2.8 is the usual standard for this kind of "pro" product.
The feeling of the 12-40mm F/2.8 lens reveals its high class all weather construction especially in comparaison with the kit zoom lenses such as the M.Zuiko 12-50mm or the diminutive 14-42mm. Control rings for zooming and focusing are fairly larger and can be easily distinctive by the touch. We appreciate that the lens hood is part of the included accessory packaged with the lens.
One of the big advantage of the M.Zuiko 12-40mm F/2.8 is surely its focal length variation starting with a real wide setting of 12mm (84 degrees of angle of view) up to an extended normal angle of view ( 30 degrees) at 40mm. I really consider that telephoto designation should start at 60-75mm focal length in M4/3 format which represent an angle of view of 20-15 degrees to make a visual difference. At that point you get a magnification ratio of 2.5-3X compare to your naked eye. The Olympus M.Zuiko 75mm F/1.8 should be an excellent complement to the M.Zuiko 12-40mm F/2.8.
Like I have said earlier the bigger dimensions of "Pro" lenses is often generating intimidating reactions from many spontaneous subjects. It is a price to pay and you may have to earn the confidence of the people you want to photograph prior to the shooting itself. Even the non-initiated person in photography will be aware of the "pro" level of your photo taking device.
The performance of the Olympus M.Zuiko 12-40mm lens is on the upper lever flirting with the stellar performances seen on the prime (focal fix) lenses. It is a good substitute product to the 12mm, the 17mm, the 25mm and the 45mm prime lenses although all theses models offer a much larger maximum aperture (F1.8-2) which support a better depth of field control.
The extended focal range of the M.12-40mm qualify it as a good urban traveller optic to keep at hand. more than on your chest. And yes it can be a good action lens.
If you are looking for a basic "pro" setting the Olympus M.Zuiko 12-40mm F2.8 will be a strong contender to fill the task. And the image results will speak by themself.