You asked
Best travel lens for the sigma bf?
For the Sigma BF, I'd start with the Panasonic Lumix S 24-105mm f/4 Macro OIS. It covers wide to short telephoto, which handles most travel pictures, and it's stabilised. That matters here because the BF has no stabilisation in the body, so the lens has to supply it for dim churches and interiors.
If you want more reach for street scenes and details, the Panasonic Lumix S 28-200mm f/4-7.1 Macro OIS stretches further, at the cost of being slower in low light.
For evenings and food, pair either zoom with a small fast prime such as the Panasonic Lumix S 35mm f/1.8. It's an easy addition to the bag, and the wide f/1.8 aperture helps in dim restaurants.
For more on packing a travel kit, see Travel.
Written by Claude from this site's pages.