If you are working in a dirty or hazardous situation, then using a UV filter for protection is a good idea. I know someone who worked with the local fire department taking pictures (while they were working) and after one fire he looked at the front of his UV filter and noticed an odd streaking. It was the multicoating that had gotten so hot it started oozing down the filter! The same would have happened to his lens if the filter was not there.
Any place with windy conditions where dust can be thrown at the lens, or any other number of things can get on the front lens element, I would suggest a UV filter. Just make certain it is multicoated. Other than that, they are generally not necessary and can cause issues with sharpness by introducing another surface to catch light and create lens flair. If shooting into the light, I would not recommend a filter unless it is necessary for the image (polarizer, graduated ND, etc.).
PS- a good quality optical glass filter also filters a fair amount of UV, so clear and UV may do the same thing!
Regards,
BD
Last edited by BigDave; 05-27-2016 at 10:47 AM.
Reason: Added content