So Ive been shooting with the S5 for about two years now and honestly I love the sensor but Im hitting a wall with my usual 20-60mm kit lens. Im planning this big solo trip to Tokyo and Kyoto in about three weeks and I really want to challenge myself to just use one prime lens the whole time instead of lugging around a bag of glass. Usually Im a zoom guy through and through but I was shooting some indoor stuff recently and the f/5.6 on the long end of the kit lens just killed my ISO levels and everything looked way too noisy for my taste.

Ive been looking at the Lumix 35mm f1.8 or maybe the 50mm but Im worried the 50 might be too tight for those narrow neon alleys and the 35 might not give me that subject separation I want for portraits of the locals. Ive got about $700 saved up for this and Im really looking for that goldilocks lens that stays on the camera 90% of the time without feeling too bulky. I know the L-mount system has some Sigma options too but Ive heard the autofocus can be a bit hunt-y compared to native glass on the S5s contrast detect system.

What do you guys think is the most versatile prime for this setup if I can only bring one?