see also:

• 3x telephoto zoom lenses for Micro Four Thirds
• 3-4x super-telephoto zoom lenses for Micro Four Thirds
• 8-10x super-zoom lenses for Micro Four Thirds
• 300mm telephoto options for Micro Four Thirds

• the best current lens with the fastest AF and wide aperture in the 135-150mm range focal length currently is the Olympus mZD 40-150mm f/2.8 pro lens which will give 150mm f/2.8 with high optical quality and weatherproofing
• if you can't afford this, there are a few other options but all with major compromises

• Olympus mZD 40-150mm f/2.8 pro lens
• very sharp lens wide open
• the problems are:
  • pity the zoom doesn't get to 200mm
  • relatively expensive (~$US1500)
• advantages:
  • only 760g w/o tripod mount
  • does not extend on zooming
  • close focus 0.7m
  • high optical quality
  • CDAF compatible for face detection and Live View AF and new dual linear voice coil motors for focusing
  • gives good depth of field (DOF) control
  • has tripod mount
  • nice bokeh
  • not too big (72mm filter)
  • can be used with Olympus mZD tele-extender (MC-14 1.4x)
  • freeze-proof
  • manual focus clutch mechanism
  • L-Fn button
  • weatherproof

• Olympus ZD 50-200mm f/2.8-3.5 lens
• AF will be stutteringly slow on most bodies, although the E-M1 will allow faster phase detect AF
• very sharp lens wide open
• at 135mm, the widest aperture is f/3.3
• the problems are:
  • slow AF
  • big, heavy lens (1.07kg), and almost absurdly long when extended even to 135mm focal length when the hood is in place (10.5cm longer than the Canon EF 135mm f/2.0L lens with its lens hood)
  • f/3.3 means depth of field (DOF) control is a little more limited
  • requires four-Thirds adapter
• advantages:
  • gives best telephoto range
  • close focus 1.2m
  • has tripod mount
  • nice bokeh for a zoom lens
  • can be bought at reasonable prices 2nd hand
  • can be used with Olympus ZD tele-extenders (EC-14 and EC20)
  • weatherproof

• Olympus ZD 150mm f/2.0 super telephoto lens
• a beautiful lens BUT AF will be stutteringly slow on most bodies, although the E-M1 will allow faster phase detect AF
• very sharp lens wide open
• the problems are:
  • slow AF
  • still expensive (>$A3000 new perhaps $A1700 2nd hand)
  • very heavy (1.6kg, 82mm filter)
    • for some reason it is substantially heavier than a Canon EF 300mm f/4L IS lens which gives the same field of view and DOF on a full frame dSLR and weighs only 1190g and uses a 77mm filter but the 300mm lens is much longer at 221mm
    • it has two big advantages over the Canon 300mm lens:
      • it can be used with a 2x TC and still have AF and an aperture of f/4 instead of f/8
      • it can be used hand held thanks to the wider aperture and the more effective IS of the E-M1 camera
  • close focus 1.4m
  • requires four-Thirds adapter
• advantages:
  • gives best depth of field (DOF) control
  • has tripod mount
  • nice bokeh
  • not too big
  • can be used with Olympus ZD tele-extenders (EC-14 and EC20)
  • weatherproof

• Canon EF 135mm f/2.0L lens
• a full frame lens
• very sharp lens wide open - almost as sharp as the Olympus ZD 50-200mm wide open at same focal length
• can be hand held on the Olympus OM-D E-M5 camera with IS on and set to 135mm, at 1/250th second with minimal loss of sharpness compared to tripod use, but sharpness will very much depend upon accurate manual focus as DOF is shallow
• the problems are:
  • no AF on MFT, must use magnified MF or other MF assist
  • no aperture control, thus at 2.5m you only get about 4cm DOF!
  • subject to internal flare
  • NOT weathersealed!
  • requires EF to micro-four-thirds adapter
• advantages:
  • gives very shallow depth of field (DOF) but no ability to increase it
  • nice bokeh
  • close focus 0.9m
  • not too big nor heavy (750g, 72mm filter)
  • weatherproof
  • not too expensive
  • can be used with Canon EF tele-extenders
  • can be used with a Metabones Speed Booster adapter to give aperture control and reduce down to 96mm f/1.4
  • can obviously work as an AF lens on Canon EOS cameras

• Olympus OM 135mm lenses
• when compact size trumps AF
• only 360g and 80mm long, 55mm filter
• will need OM-MFT adapter
• built-in lens hood
• best stopped down to f/4 to reduce purple fringing