Hey I've been a long time reader of this website but finally decided to register because I need some lens advice. I do a lot of backpacking and try to keep my kit as minimal as possible. Im looking for a great landscape lens but also a fast lens for landscape astrophotography. I'm looking at the 16 -35 f2.8 II but have heard a lot about it being very soft in the corners. I've also looked at the possibility of the 16-35 f4 and possibly a wide fast prime? I'm currently shooting with the 6d and the 24-105 and the sigma 15 mm 2.8 fisheye (I also shoot a lot of skateboarding) the 50 1.8 and the 100mm f2.8 macro. I love the fisheye but don't want that much distortion with the landscapes. Ive looked at the new Tamron 15 - 30 2.8 and it's getting mixed reviews so far. My main hesitation with that is that I want to be able to use filters with it. Im willing to spend around $2,000 for either a lens or lens combo. Anyways if you guys with your expertise and real world knowledge have any advice I would greatly appreciate it. Thank you.