Hi all, I am in a unique position that I will be looking to purchase a new lens in the near (next couple weeks) fast telephoto prime lens. If you look at my history I use a variety of Canon, Sigma and Olympus adapted lenses so I am well versed in their behaviour but...I`m after a bit of advice as to what approach you would all take. All lens selections would be second hand as I will be buying from Japan. Olympus 150mm F2.0 - we have all seen what it can do but its slow focusing and 4/3's compatible. This was my first choice but at about $1200-1500USD its quite expensive for second hand examples. Canon 200 2.8L II + Viltrox EF-M2 - This brings it down to 142mm @ F2. Almost equivalent to the above but obviously adapted. It has a USM motor and I can get the whole combination for under $900USD. There is a risk that the adaptor doesnt work but I`m happy to concede at 200mm 2.8 and buy a kipon or metabones .7 speed booster. Sigma 120-300 2.8 + Viltrox EF-M2 - is on the list and brings in the fact that its a 2.8 zoom lens but cost is significantly higher. I would be looking at the older model which can be had for under $900USD plus the cost of the adaptor for a total of about $1050 USD. If i can't find the older non OS version then the price would likely double. This would be a 84-210 F2.0 lens with the speed booster attached which is absolutely insane and provide a flexible range to complement a 50-150 2.8 and 17-50 2.8 lens set with the speed booster. I do wildlife photography (some birding) but as my targets are generally land based or in trees i can do without the crazy focusing abilities. I`m after low light monsters and I`m keeping in mind that I may flick over to full frame in the future and buy an A7II and adapt the lenses I have. Thoughts? Or am I insane? Before anyone says anything I run the 18-50 2.8 and 50-200 2.8 four thirds combos on an e-m1 so I`m not neccesarily interested in scrapping everything and buying the 12-40,40-150 2.8's.