The Micro Four Thirds camera system is getting some very nice lenses, but in the telephoto range, there are still none faster than f/5.6 at the 135mm native focal length although there is a Lumix 100-300mm f/4-5.6 OIS coming next year which will give ~f/4.0.
You can use a Four Thirds ZD 50-200mm f/2.8-3.5 or the superb ZD 150mm f/2.0 lens, but neither will AF on GH-1, and will AF slowly on an Olympus Micro Four Thirds, not to mention, they are both really too large for this format camera.
Here is where the beautiful compact Olympus OM lenses can come in (even better if you have an Olympus camera so they become image stabilised).
The Olympus OM 135mm f/2.8 has become a permanent fixture in my Micro Four Thirds walk-a-round kit as it gives you 2 extra stops of aperture compared to the Lumix 14-140mm HD lens which allows faster shutter speeds to stop moving subjects better, allow lower ISO for low light video on a tripod, and allow more background blurring.
Here are a few examples of it hand held on the Panasonic GH-1, and thus without image stabilisation, all at f/2.8, no sharpening or cropping:
Sleeping on the edge:
Sulphuric acid and the peacock:
African musician at Melbourne’s Moomba festival:
And to test the bokeh, it does quite well with annoying background highlights with minimal hard ringing:
If you do not wish to have 270mm equivalent focal length field of view in your hand at f/2.8, you can opt for the slightly smaller, but easier to hand hold without IS, the Olympus OM 100mm f/2.8:
The Olympus OM 100mm f/2.8 with OM-EOS adapter on a EOS-M43 adapter (yep, that gives 200mm field of view at f/2.8 – now that’s what I’m talking about for compact size!):
Memo to Panasonic and Olympus: PLEASE give us a compact telephoto with wide aperture, and if it is a Lumix, it will need to have OIS – in fact why not make a 100mm f/2.0-2.8 macro OIS and a 150mm f/2.8 OIS.