You asked
Is the pentax smc da 16 50mm f 2 8 ed al if sdm good for travel?
Yes, for most travel, with one caveat. The lens covers the wide-to-standard range you'll use most, and on APS-C it frames like 24-75mm on full frame, so one zoom handles landscapes, streets, food and people. The f/2.8 aperture helps in dim churches and restaurants, where you can keep the shutter speed up.
The caveat is that this lens has no stabilisation. For handheld interiors at slow shutter speeds, pair it with a Pentax body that has in-body stabilisation, as the travel guide suggests. Check the body's specs before you buy.
If you want something to compare it with, the Pentax smc DA 16-45mm f/4 ED AL is also an APS-C zoom, though I have less to say about it here.
Written by Claude from this site's pages.