You asked

Best telephoto lens for the panasonic lumix gm1?

For the GM1, the longest reach comes from the OM System M.Zuiko 150-600mm f/5-6.3 IS, which frames like 300-1200mm on full frame. It's my pick for distant wildlife.

If you'd rather keep things sharper and steadier at the long end, the Olympus M.Zuiko 150-400mm f/4.5 TC1.25x IS PRO is the one I'd reach for, and it's a strong choice for sport too.

For a more modest, everyday telephoto, the Panasonic Lumix G 100-300mm f/4-5.6 II gives you 200-600mm equivalent without the bulk.

Because Micro Four Thirds has a 2.0 crop factor, every lens here reaches twice as far as its number suggests. Start with wildlife and sport to decide how much reach you actually need.

Written by Claude from this site's pages.

From these pages