Should I use a UV filter or not?

In the days of film, UV (ultraviolet) filters were often used, whether to reduce haze in shots that included long-distance detail, or to reduce the bluish tinge that UV light could impart in long exposures or certain conditions.

In modern times, with new glass coatings and advanced sensor filters, UV light is often mostly filtered out by the lens glass itself, and most of the IR (infrared) light by the sensor filter itself.

So why do people still use UV filters?

Some still use them because they've been used to them from the days of film, but most people use them as a 'protection' filter. This means, they hope that the filter will take the brunt of damage in case of conditions that would be adverse to lens elements. The debate on whether or not to use UV filters in this fashion is widespread and opinions differ on both sides of the fence.

As always in cases like these, both sides have their points.

Consider that the UV filter is essentially a piece of glass. If this piece of glass is not of good quality, or manufactured correctly, you will get all sorts of aberrations and image degradation, including softness, loss of clarity, loss of contrast, colour desaturation or shifting, all of which seriously impact the final image. Putting on a UV filter essentially adds another element to the front of the lens, reducing transmissivity of light, especially in cheap filters.

Using a better UV filter, say a B+W, will cost alot, often up to 100-150 euros depending on the size of filter. These filters have much less negative impact on the final image, although in sunny conditions they can increase the chances of glare, and at night, may cause or increase the chance of ghosting (reflections of lights on the filter).

Also, for general protection against catastrophic accidents like dropping a lens, the cost of homeowners insurance that covers all your equipment, or even the cost of replacing the lens front element, can often be about the same as that of buying a good UV filter.

Thus it could be argued that exposing the front element in order to maintain image quality is a good tradeoff. Additionally, in many cases, the filter itself can cause more damage to the lens, as when it shatters, pieces of glass can scratch the lens badly, or the filter ring can bend and be very difficult to remove.


But what about situations such as the beach where there is flying sand?

Well, the lens coatings on most modern lenses are surprisingly tough. I have subjected my 17-55 to many different conditions, including very windy beaches, and the front element looks just as when I first bought it new. Unless there is an actual sandstorm, most conditions will not harm your lens.

That said, I do use filters for protection, for example when covering speedball matches. When there is a small projectile travelling at 300 feet per second, hopefully the filter will absorb the brunt of the impact before the lens itself.


But just in case? I don't want to lose my lens just because I get a scratch?

It's always understandable that one wants to protect one's investment, especially those who are not professional photographers. There is nothing worse than saving for months and months, and not being able to use a lens because of accidental damage, or wear and tear.

However, the true impact of a damaged front element on image quality is negligible, even in significantly damaged lenses. A damaged back element would be much worse. Even deep scratches on the front element can be painted in black (to reduce sunlight reflecting off these scratches) with very little image degradation.

For proof:


http://www.lensrentals.com/news/2008.10.30/front-element-scratches


http://kurtmunger.com/dirty_lens_articleid35.html

SPOILER ALERT: These two articles test a lens that has had its front element literally shattered, and show the images that it produces. You might be surprised (if you haven't already read them) what a lens you'd think was only fit for the bin can do!

So there is no point using a UV filter?

I wouldn't say so. UV or protecting filters have their time and place, where the risk of damage to your lens element is high due to airborne projectiles, or areas with chemical corrosives in the air.

Additionally, if you are deciding to sell your lens in future, being able to say that you always always used a UV filter can increase your sale price.

Also, some people prefer using a good UV filter for peace of mind, and removing it when they notice ghosting or other effects. 

Personally, I would use a lens hood. A lens hood portrudes far out from the front element, and if dropped, will take the brunt of the impact, shattering and dispersing the kinetic energy, or merely bending and flexing. Additionally, it protects from light rain, reduces glare and thus can actually improve image quality!

In any case of lens trauma, there is also possible shifting of the elements out of alignment, which would be far more noticeable.