I thought I was high enough on the rocks so that the salt spray of the waves wouldn’t get to me... I was wrong... A big one hit and my camera and I were spattered. But a UV filter saved the front of my lens from taking a direct hit from the sea spray that contained on only salt water but silt and not so fine sand as well. This is what you DON'T want see coming directly at your lens. The lens was “water-resistant but with salt water all bets are off. The lens was OK after I quickly wiped it off but that would not have helped the front glass of my lens if it didn’t have a filter over it.
There is a lot of options and more than a little misinformation out there regarding UV filters. So I wanted to bring up some facts given my years, decades actually, of experience as a photographer and as someone who has worked for filter distributors and manufacturers.
First, what is UV? Ultraviolet (UV) light is the light that boarders the lower end of the visible spectrum. The visible spectrum is between 400-700nm and UV spectrum is between about 280-430nm. This is light that your camera’s sensor is not completely calibrated to and the more UV present the more of a negative impact is has on your photos. UV light contributes to atmospheric haze that makes scenic photos less sharp.
So what does a UV filter do? It does two things. One it does all the time and the other depends on your location. A UV filter over your lens will always protect the font element of your lens all the time its on. Keep in mind the front element is the largest and most expensive piece of glass in your lens and replacing it is one of the most expensive lens repairs. It protects it from everyday bumps when you are out shooting. It also protects it form wind-blown sand, salt spray, mud, or if you scramble over rocks with your camera on a strap to get to where you shoot. Under these conditions a UV filter should always be on the front of your lens.
Beyond that the effect of a UV filter depends on your location, or more accurately it depends on your altitude. UV light is filtered out as it travels through the atmosphere so there is more UV light present at higher altitudes than there is closer to sea level. Using a UV on the rocks boarding the Pacific Ocean as I was doing early was not as much about filtering out UV as it was about protection. There is still some UV light present that day it was about protecting the front element of my lens.
But when photographing at higher altitudes above sea level there is a lot more UV light present and even more UV as you go higher. A UV filter will improve the sharpness of the sweeping scenery I came out to shoot and have the added benefit of protecting my lens. This scenic photo from Valle de Bravo, Mexico was taken at over 6,070 feet (1,859 meters) above sea level. For comparison, the "Mile High City" of Denver, Colorado sits at 5,280 feet (1,609 meters) above sea level.
Even higher than Valle de Bravo is Mexico City and the Pyramid del Sol in the Teotihuacan, a UNESCO World Heritage site. Both sit on the same plateau at 7,380 feet (2,249 meters) above sea level. More UV makes scenic photos in these higher elevations more hazy and less sharp. A side note, there is also less oxygen at these altitudes so while hiking up the several hundred steps of the pyramid del Sol you get winded much more quickly. I raced to the top and it took 10 minutes to catch my breath and stop shaking.
“A $2,000 lens with a $20 filter is going to preform like a $20 filter.”
“So I should just get the cheapest UV filter I can find, right?” ... WRONG! One of the “purist” arguments against UV filters or any filters for that matter, is that they are “inferior” glass that can degrade your image. People promoting this argument have not kept up with the times or filter technology. This is true if you choose a cheap filter form a company you have never heard of on amazon.com or eBay. These filters often do not have true UV optical glass in terms of the quality and formula of the glass as well as precise grinding and polishing of the surfaces of the filter. The reason they can call them UV is because all glass filters out some, if even just a little UV but can degrade sharpness and cause inaccurate colors if the glass they use is not formulated optical glass.
Remember: A $2,000 lens with a $20 filter is going to preform like a $20, pure and simple. Make a wise choice when choosing a filter.
If the choice is between a $20 (or even less) filter or no filter at all, go with no filter. No filter is better than taking a chance on a cheap piece of glass. In that respect the purist are correct. No matter how much your lens cost, you made an investment in it so make an investment in the filter to protect the lens and choose a filter that is going to protect your lens and improve your pictures, not harm them. High quality filters are cheap insurance for the front of your lens and will help improve your pictures.
Buy UV filters from established brands known for optical filters and who’s roots in optics go back decades. Some of these include Hoya, B+W, Kenko, Schneider and just a couple others. These filters use specifically formulated optical glass that is formed, ground and polished for perfectly flat smooth and parallel surfaces. These filters are multi-coated like your lens is multi-coated to reduce reflections that could degrade your photos. So using a high quality UV filter will not degrade your images but only help improve them and protect your lens.
Next, make sure the filters are multi-coated and in some ways the more layers of multi-coating the better. Lens manufacturer go to great lengths to multi-coat their lenses to avoid reflections and putting a non-multi-coated filter in front of your lens is almost same as shooting through a window. You would do that to get the best pictures so make sure the filters you buy us high-quality multi-coating.
Through my entire time in photography, which goes back decades, I have only used Hoya filters so they are the brand I know best and have the most experience with. The HMC Skylight 1B filter over the lens of my first “real” camera, a Canon AE-1 was a Hoya and I have used them ever since. By the way, I was 13 years old when I got that AE-1. Glass and multi-coating technology have made great leaps in the last 30 years. The current generation of Hoya UV filters, the HD series with chemically hardened glass and ANTISTATIC series with hardened coatings that negate static build-up have up to 16 layer (HD) of multi-coating on both front and back sides of the glass to reduce reflections. Both series are some of the best filters that money can buy bar none.
So remember, you made an investment in the lenses you shoot with so extend that investment by protecting it with a high-quality UV filter that will not only protect your investment but also help improve your pictures.