When I started out I had a UV filter in my 28-70mm lens to protect the front element against damage and dirt. It made the hood difficult to get on and off and became quite stuck to the front of the lens and hard to remove when I did want to remove it. Plus it made it impossible to use my rectangular grad filters as their holder screwed into the same thread as the protective filter. Then I fitted a protective filter to my longer lens which was already slow focussing and my perception was that the extra glass slowed it even further. Eventually I stopped using protective filters totally, I always use the hood which seems adequate protection and normally my lens front elements don't get too dirty, not more than an occasional brush with a lens pen can't cope with. So, what do you do? Do you swear by protective filters or just use the hood?