The Olympus M.Zuiko Digital ED 12-40mm f2.8 PRO ($999.99 direct) was launched along with the company's top-end OM-D E-M1 camera , adding a true professional-level zoom to its Micro Four Thirds lens library.

Maximum f/2.8 aperture throughout zoom range; Very sharp from edge to edge; Focus clutch system; Protected from dust, splashes, and cold temperatures; Minimal distortion

Expensive; Lacks optical image stabilization

This standard zoom lens for Micro Four Thirds (MFT) system cameras provides an angle of view equivalent to a 24-80mm lens used on a 35mm format camera and sports a constant f/2.8 maximum aperture throughout the zoom range.

I love this12-40mm f/2.8 lens! With a constant f/2.8 maximum aperture, I can take available light photos that previously would have required use of a flash. And, the photos at all focal lengths are noticeably sharper than what I was accustomed to with my previous lens.

It is big and heavy and operates buttery smooth. If you are looking for image quality close to the primes in this range, but would rather have weather sealing then this lens will get you closer to anything else on an Olympus camera.

Durable; Easy To Use; Reliable

Bulky

This is the second best lens I have owned in almost 50 years of photography. The best is its companion 40-150 F2.8 Pro lens. A little larger and heavier then some m4/3 lenses but not so much as to be a problem for me. Optical quality is great at all focal lengths from F2.8 through F8.0.

Fast; well built; close focusing; weather resistant; sharp

EDIT: Thought of one; The auto manual clutched focus ring can be a little loose; Easy to bump it from auto focus to mechanical manual focus; Minor issue but I've done it a few times; Would be nice if it was a little stiffer to pull back

Micro 4/3's is not a very good at fast action photography, like sports or running children, this lens makes it more tolerable.

High quality piece of glass! Takes outstanding photos on my EM-5; Comes with a lens hood; This is truly a Pro lens

On the expensive side if your a novice

great lens with wide zoom range and fixed aperture throughout. Pictures appear to be very sharp, autofocus is very fast, good build quality (but lens extends when zooming). 62mm filter size.

fixed aperture; sharp images; weather sealed

lens extends with zoom

I bought this because it's received great reviews and I wanted to replace my kit lens, but after getting it, I returned the Olympus 12-40 2.8. Let me explain with some pros and cons.

I like this lens as my walk around lens. It is light and fun to use. Great package with the E-M1. Optically it is mostly good apart from the issue with ghosting and flares.

- perfect size and weight for my E-M1; sharp (I have never noticed the tested weakness in resolution at 40mm in real world); fast AF; water resistant (after about one hour in moderate rain and humidity at about 100% the lens became foggy from the inside and after half an hour in my bag it was ok...

Work with bright light sources in the frame; If you have bright light sources in the frame (e.g; candles at night) they cause annoying ghosting and flares; I hate this this behavior in the dark; In daylight it is usually acceptable.

I always find the wide angle lens purchase so difficult a decision. I have used the Panasonic 14-45mm as my general purpose lens since the G1 was released. And more recently on the OMD series camera bodies.

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