Its better to purchase a UV filter with the camera because you must be needing it because of the reason that it protects you original lens from dust and scratches. Keep this on all the time on the camera.

A simple ultraviolet filter may be available in market for $5 to $20 so you might not be worried about it to be scratched up instead of a $500 lens.

Why UV filters are used?

Mainly photographers use UV filters to reduce haziness caused by ultraviolet rays. A UV filter is transparent and you can keep it with your camera all the times. There are different type of UV filters like UV17 that cut down the light effects considerably or reduce purple fringing in digital cameras. These type of strong UV filters can also be used for warming color photos taken in shade in daylight.

There are wide varieties of UV filters available in market, you might select a high quality or bit expensive filter as it is noted that in lower quality UV filters photographers sometimes face problems with auto focus and image degradation have also been noted.