The Australian site Photoreview tested the new Panasonic 100-400mm lens:

Subjective assessment of images taken at other focal lengths implied image sharpness was maintained up to about 250mm, after which it began to tail off a little. However, images were still nice and sharp at 400mm and judicious application of unsharp masking before printing yielded excellent results.

Some people may think AU$2199 is a lot to pay for a fairly specialised lens. However, we feel this lens represents excellent value for money, particularly when compared with similar lenses for DSLR cameras, which weight several kilograms more and cost at least four times the price of Panasonic’s 100-400mm f/4.0-6.3 lens.

Mirrorlessons writes:

I’ll say it up-front: the Panasonic 100-400mm really surprised me. I wasn’t expecting the lens to be that sharp at all focal lengths and the fastest apertures. Although I used 300mm and 400mm most of the time for my wildlife photos, I also found it helpful to be able to pull back to 100mm. It can be an excellent choice not only for birds and wildlife but also for outdoor sports and other applications where a long lens is required.

Camerastuffreview writes:

The resolution (in lp/mm) of the Panasonic 100-400 mm is so high that a 24-megapixel camera with a larger sensor takes pictures that aren’t any sharper. You will not be bothered by vignetting and distortion. Thanks to the built-in image stabilization, you have a quiet viewfinder image when you shoot by hand, are less likely to get a motion-blurred shot in low light and get quiet video recordings. The robust construction and the extra sealing against dust and splashwater make this super-telephoto zoom perfectly suited for use under the most extreme conditions. Micro-43 users had to wait a long time for this lens, but it is worth the wait. This is an absolute winner.  

Really a great lens!

Panasonic-Leica 100-400mm preorder links at Amazon, Adorama, BHphoto, FocusCamera and Panasonic. In EU at Technikdirekt, Cyberport, WexUK. Fotosidan.

43rumors reader Dave sent me a huge file (download the PDF here) whcih collects all the MTF charts from MFT lenses (Some of the MTF charts are from DxO and ePhotozine). Dave writes:

“The object of the exercise is to present the bulk of the Olympus, Panasonic and third party lenses for the Micro Four Thirds (mFT/m43) compact system camera mount in one place, grouping lenses that might be the subject of some comparison prior to purchasing. (You can cut and paste rows if  necessary.) Only lenses native to the m43 system and the prior Four Thirds (FT) mount – which can be used with an official system adapter – are shown. Bear in mind that FT lenses from third parties are usually re-purposed full frame and APS-C sized lenses and as such are often significantly larger and heavier than even their native Four Thirds counterparts, let alone their m43 descendants. The point of considering older FT and compatible lenses really comes down to two features: the fact that some older lenses can be had quite cheap and that lenses designed for a larger format utilise just part of the image circle. This second aspect means that those lenses that typically score poorly when paired with a larger sensor can actually be quite good on the smaller FT sensor *, as the corners and edges are cropped away.
Equally, some of the more modern native mount lenses with large, fast apertures (for example the Voigtlander Hyperprimes) are big and heavy by m43 standards. Other specialist lenses, such as those for cine and special effects are not shown, as I think people wanting those will not really want or need to compare them with standard lenses, nor may sharpness be the starting point for a comparison.

* Note that the FT and mFT sensors are exactly the same size – it is just the flange distance that differs. You can use an older four thirds lens on the newer micro four thirds bodies with an adapter, but not the other way around. However, focussing performance is generally significantly poorer for the older lenses.“