I am leaving for Tokyo in exactly twelve days and I am currently having a total gear crisis with my a6700 setup. I've been shooting Sony APS-C since the a6000 days so I know my way around the E-mount ecosystem but this new body is making me rethink my entire travel strategy. I usually carry the Sigma 18-50mm f2.8 and while it is tiny and sharp as hell the reach is honestly killing me lately. I was out doing some practice shots at a local street fair last weekend and I kept wishing I had more than 50mm without having to stop and swap to my bulky 70-350mm every five minutes. It is just too much friction when you are trying to actually move through a crowd and keep up with people.

My bag is getting way too heavy for a carry-on only situation and I really need a one-lens solution that can handle everything from tight Shibuya alleys to distant architecture. I looked at the Tamron 17-70mm f2.8 because everyone raves about the constant aperture and the internal stabilization but man that thing is a total brick. It almost defeats the purpose of having a compact body like the a6700 if I'm basically carrying a full-frame sized lens. Then there is the Sony 18-135mm which has the perfect range but I am worried the variable aperture is gonna bite me once the sun goes down or when I am inside temples where lighting is hit or miss.

Budget is around 900 bucks give or take but I need to pull the trigger tonight so it gets here in time to test the tracking before the flight. Is there something I am missing here? Maybe a lens I havent considered that hits that sweet spot of weight and versatility? I need to know if the 18-135 is actually good enough for someone used to prime-level sharpness or if I should just suck it up and carry the heavier Tamron for the f2.8. I've even thought about the 16-55mm G but it has no OSS and I'm not sure how much I can trust the 6700's IBIS for video while walking. What are you guys actually using as your primary workhorse for a three week international trip where you can only bring one zoom...