Originally Posted by
diburning
You kit lens is not weather sealed. As such, there are gaps where dust can get in. Higher end lenses have weather sealing, which also includes a rubber gasket on the lens mount to make it harder for things to get in.
So what type of lens should I get? I seldom need anything more than 150mm. Most of my shots are 18-75mm. I take a lot of streetscapes, long exposures at night of skylines and so forth.