The 100-300 is an amazing lens for the money, quite how Panasonic have made such a good lens for the weight and price is amazing. I had one for about a year and was always pleased with the results. It is plenty sharp enough when shooting wide open but obviously does improve when stopped down a bit. The AF seems to be decent enough on it though this is clearly effected by the body it is used one. The best body I put it on was a G3 and I am sure it would be even better on a newer model. I used it alongside a Canon 100-400 and in good light the Panasonic compared very well. It is not quite as good as the Canon but at ~1/3rd the cost that is hardly surprising. I would say that the 100-400 is a better lens (I still have it but have sold the Panasonic) but the Panasonic is much better value.

One huge advantage of the mirrorless cameras is that you do not get issues with back/front focusing as you can on a DSLR. Not the biggest issue but it is nice to know that any camera bought on a mirrorless system should focus acurately even if not as swiftly as on a DSLR.

I got to have a play with a Sony NEX 5n with the 16mm f2.8 at the weekend and was very unimpressed. The Sony menu system is the least user friendly of any that I have tried. If you want to have any control over the camera settings you have to work hard. I was also unimpressed with the image quality, it was fine in decent day light but was poor in low light or when using the bundled flash (seemed to always fire at the same power so the subject needed to be the right distance away to get a decent result).

I've found that when the Panasonic seems to be struggling to focus on the subject wanted, if I manually focus somewhere near enough to 'give it a hint' so to speak, then it locks on quite well. It's one of those things where you have to keep trying stuff out to see how it works and eventually you get to use it instinctively - though, to be honest, I haven't had the time that I'd like to use the whole kit as much as I'd like recently.

DXO rates the Olympus 75-300mm lens as a bit better than the Panasonic 100-300mm, but it doesn't have the close-focus at the long end of the zoom range to give a more comfortable working distance for nervous butterflies, dragonflies etc. The Olympus, of course is a bit slower (F6.7) at the 300mm setting, though it's a bit lighter in weight but doesn't include a lenshood (or pouch case) in the package.

A couple of shots with the Panasonic at 300mm on my E-M5 below. The Banded Demoiselle damselfly is one I've already put in my 'Birdforum' gallery and the Iberian Marbled White butterfly is one I placed in the 'Surfbirds' insect gallery as that species hadn't been featured there before:

Mike I do not think you will see much of a drop in IQ with the latest Sony sensor used in the latest Olympus cameras.

Like you I am a pensioner and camera weight has a big influence on me and a few months ago I sold all my DSLR kit and went completely MFT.

Most days I walk the dogs around the local country park and my carry round kit is the E-M5 or E-PL5 and the 40-150mm (80-300mm) kit lens which is very light and you can carry it around all day. Hell if I pack big and take the 40-150mm f4-5.6, 14-42mm , 17mm f1.8 and 45mm f1.8 it all fits in a small bag that you would be lucky to fit a decent sized slr and standard zoom in.

Back to IQ, I cannot tell you if it is good enough for you, all I can do is post some real world images and some 100% crops. All the info is at the bottom of the images.

All images taken on my dog walks with the kit m40-150mm lens.

Thanks Paul. I am not quite ready yet (funds!) but when the time comes I think I will have to go to a supplier and actually handle several micro2/3 cameras and look at their menus etc but they look promising for what I want. Better the camera with you than the one at home because that one is too heavy!

Indeed Mike trawling through those menus can be a little bit daunting (and although there is a lot that can be customized) it is the reason why I set Olympus to use the Super Control Panel.

Just push the OK button and all the major setting that there are not buttons for come up on the LCD or in the viewfinder and you just select the one you want to change with the DPad or top wheel, makes it a lot easier for a old un like me.:)

Useful and quick.