One of the most common dilemmas among beginning photographers regards filters. They see them on other people's lenses then look at the lens cap their kit lens was supplied with and ask themselves what are those filters for?
Well, we're here to answer all your questions and guide you so that when you go shopping for filters, you'll know exactly what to buy. Let's start with the very basics.
The UV filter
What is a UV filter and what is it used for? Well, it's the single filter that can go totally unnoticed if you don't have a trained eye to spot it. It is completely transparent and it goes screw mounted on the front of your lens. They're also called haze filters.
Back in the forgotten days of film photography, UV filters were used to prevent haziness or fogginess from sunlight. As a medium, it was a lot more sensitive to such effects than digital sensors are. A standard UV would filter sunlight and block shorter ultraviolet waves. They are occasionally referred to as L37, for filters that remove UV light with waves shorter than 370nm, and L39 for those who remove wavelengths shorter than 390 nm.
Now, since all this is part of what UV filters were originally created for and it's not that useful in the present, why would you still buy one? A couple of reasons actually.
First of all, the haze effect can still occur in digital photography. Today's UV filters are designed specifically for digital sensors. Without getting too technical, even though the chip in your camera replaces the film frame and works pretty much the same, light is exposed differently onto a sensor. Thus, older UV filters aren't as effective as present day ones.
But the haze argument isn't the most important. Protection is. You might not realize the importance of protecting your lens if you're using a standard kit zoom, but I guarantee that after you spend $1,600 on pro glass, you will do anything in your power to keep it safe. The UV filter comes between the lens's first glass element and everything that might harm it: dust, scratches, fingerprints, baseball bats or whatever it is you point your camera at.
Do UV filters affect exposure in anyway? Absolutely not. That's why after you put in on you don't have to take it off again. So why some UV do filters cost more than others since all they do is protect?
This is a very good question a lot of photographers don't know the answer to. The answer is in the glass. The more you pay for a UV filter, the more layers of coating it will have and the stronger the glass will be in case of impact. Your lens will be better protected and so will your image sensor.
If you could have only one filter in the world, the UV should be it. You mount it on the lens, forget about it and add as many other effect filters as you like.