I would like to add an ultra-wide into my setup for landscapes and interiors. The two requirements are it has to be below $500 and accept filters. Size is not a primary concern, but bonus points for balancing well on an E-M5 with grip. Manual focus and aperture is also 100% acceptable. That instantly knocks out the Panny 7-14mm. My current three ideas are: Olympus m.Zukio 9-18mm - About $500 to $550 used (haven't found any under $500 yet) Olympus Zukio 9-18mm w/ cheap ebay MMF 2 knock off - About $400 to $450 Sigma 10-20mm w/ cheap focal reducer - About $450 to $500 (Not sure if a DX lens w/ focal reducer works or not) The side advantage to the 10-20mm is that focal reducer, which would also work with my 55mm f3.5 pre-AI Nikkor, which may be my all time favorite lens on any camera, as long as you don't wash out the sky or point it into a light source. Thoughts, other ideas?