I'm looking for a 21mm/28mm RF lens. My preferences is size and 39mm filter threads, and chrome (the color is more of a minor thing) The CV lenses seem the most suiteable. how are the LTM versions of these lenses? Experience? Comments on build, optics, ergonomics? I prefer Leica for 35/50/90 but it's hard to ignore CV for 21/28.