Still thinking about this. Anyone use the C/Y 100-300 vario sonnar? Read pretty good things, but assume it is heavy and don't know if competitive with other options. The Leica M 135/3.4 seems good quality and half the weight of the Zeiss 135/2, tho not quite as good, slower, and does not take extenders (and not cheap). That plus the R 180/3.4 would be good but together, they weigh more than the Zeiss 135/2 by half a pound or so. I suppose the R 180 takes the 2x extender giving reach to 360, but slow and I have no clue about the optical quality. The Zeiss may be the best bet, but it seems like a beast with an adapter and extender on a poor little A7r....just not sure if I would then leave it home unless I had a specific mission in mind....