Ok i have narrowed the field down to Tamron adaptall 300mm f2.8 MF becomes semi autofocus 510mm f4.5 with 1.7x adaptor (450mm 2.8 and 760mm 4.5 on digital) Tamron adaptall 400mm f4 MFbecomes semi autofocus 680mm f7 with 1.7x adaptor (600mm f4 and 1020mm f7 on digital) Tokina 300mm 2.8 MFbecomes semi autofocus 510mm f4.5 with 1.7x adaptor (450mm 2.8 and 760mm 4.5 on digital) i have read favourible reviews of both the 300mm 2.8s but can find little on the tamron 400mm f4 other than an olympus site which states that it works better with teleconvertors than the 300mm 2.8 or even the zuiko 350mm 2.8. In your opinion which would be the better bet- mainly for birds and wildlife.
