UV filters help to filter out the UV rays in the environment from entering into the lens which leads to haziness in the pictures. The result, the contrast will improve & your pictures will become much more sharper in appearance. The UV filters were very much effective for one shooting film but with the digital era, their effectiveness seems to be debatable. Since digital sensors provide protection to filter out the UV rays, their seems no reason to use a UV filter on your DSLR anymore. However I strongly recommend you put one on your lens.
The prime aim of putting a UV filter on your DSLR lens is protection. Often you encounter people who just grab hold the DSLR from the lens without thinking twice that their handling will put fingerprints, oil stains etc on the front lens elements. This might even happen unknowingly even if you take utmost care to avoid it. In this case, a UV filter comes to your help. It will take all the fingerprints & oil stains and keep your front lens element squeaky clean.
Similarly if you shoot near water bodies, you ought to have an UV filter on your lens. The salt spray & sand can cause serious damage to the front element of the lens. Overtime, its coating will get damaged & the lens will fail to produce the fine image quality it used to before. In this case too, it helps to have an UV filter which you can quickly wipe off after shooting. Recently, on one of my shoot near sea-shore, it was windy & raining. The sea was throwing up huge amounts of salt water in the air. In such a scenario, the UV filter on my lens helped a great deal to keeping the lens clean. After returning home, the UV filter took some real tough cleaning to get it to be squeaky clean again. I was grateful to it, as without it my front lens element could well have taken a nasty beating of salty sea water which can often cause havoc if your lens is not weather sealed. A UV filter often can expand the life of your glass(lenses). Ultimately you may change your camera bodies but its your lenses which you’ll keep with you for times ahead.
Also there are some lenses, which require you to put a filter to make them totally weather sealed. For e.g. The brilliant Canon EF 17-40mm f/4L USM lens manual states to put a UV filter to make it absolutely weather sealed.
However, by recommending to put an UV filter on your lenses, I don’t mean any UV filter. I mean only the best UV filter. HOYA, is what I recommend. They make excellent filters & you can get as per your budget. Their top of the line filters may be expensive but they are worth it. Using cheap filters often do more bad than good to your image quality. They cause lens flare, vignetting, softness & host of other optical problems. So make sure you get a high quality UV filter(and other filters too) & do not try to save money here. The lens quality of any lens will degrade if you screw in a cheap low quality filter over it. Some good brands I recommend are HOYA, Tiffen and B+W. Stay away from local brands. Ultimately, it makes no sense to put a cheap local filter on a top of the line lens.
[Flipkart is a good place to order UV filters & other things from. By ordering from flipkart using the link above, I get a certain percentage from the amount of your purchase. It does not adds to your purchase as you will need to pay exactly the same price. You're free to NOT use this link, if you wish to. Using this link, will earn me some money which will help me to continue publishing interesting posts here. Thank you for your purchase. :) ]