Everything You Need to Know About UV Filters

When I first heard that some of my photographer friends don’t use lens filters, I was shocked. To me, a lens filter was never an afterthought, it was something you always purchased with the lens in order to protect the glass from nature. The moment the lens comes out of the box, immediately a filter is screwed on, forever sealing off the front element from the elements. 

One evening while second shooting for my friend, Eric Lundgren, I noticed something strange happening. We were shooting wedding dances inside a barn where the only lighting was provided by Christmas lights that were strung along the length of the ceiling. Looking at the back of my camera, I noticed that my photos had glowing green orbs sprinkled throughout the images. They had the same pattern as the string lights above, so something was causing the light from them to refract and ghost. After the dances, I showed the photos to Eric and asked him if he had the same problem. He showed me a few of his images, and sure enough, no green orbs were present. 

We were using similar cameras, lenses, and even settings for our images. The only difference between our setups was that my lens had a B+W UV Haze lens filter on, while Eric’s didn’t. I decided, nervously, to remove the filter for the rest of the night. The orb-like lens flares vanished from my images.

Asking around my local photography community, I found the topic to be divisive. Some believed that lens filters were necessary for protecting your lens. Others believed that lens filters were nonessential and reduced image quality and clarity by adding an extra layer of glass.

Personally, I believe that lens filters are necessary for protecting lenses and that I would continue to use them. I also realized just how important it is to invest in a quality lens filter. The world of protective lens filters, however, is a confusing place. Filters have their own marketing language, using words like Schott glass, nanocoatings, ColorCore, and acronyms like HD3, MRC, HGX. This confusing nomenclature leaves a lot for a consumer to decode. To add to the confusion, a higher cost doesn’t always correlate to a better filter.

So what should you look for when shopping for a lens filter? Let’s break it down.

Light Transmission/Reflection Rate

Light transmission would be the most important factor. The higher the light transmission value, the more light passes through the filter. Light that is reflected back degrades image quality by decreasing contrast, causing lens flares and ghosting. This value is usually expressed as a percentage— anywhere between 90-99.9%. Companies that use reflection rate express the number by subtracting the light transmission rate from 100. For example, a filter with a 99% light transmission rate has a reflection rate of 1%. 

To summarize, the higher the light transmission value- or the lower the reflection rate- the better the filter.

The B+W UV Haze filter I had on my lens while shooting with Eric, has a reflection rate of ~3%. Even though that's a very small percentage, it was enough to cause the ghosting I saw in my images. A high-quality filter should get as close to 100% as possible, and should always be under 1%. The filters I use now have a reflection rate within a 0.01-0.03% range.

Slim Profile

While it doesn’t have to be paper-thin, a lens filter should be small. Budget filters with large, thick rings can cause unwanted vignetting or light falloff in an image. It’s more likely you’ll only see this on a wide-angle lens, though it's not unheard of with standard focal lengths as well.

You’ll also want to ensure that the lens filter isn’t too thin. If it’s touching the front element of your lens, it’s likely it will cause scratches. Some cheaper “ultra-thin” lens filters have been known to cause damage. Always ensure the filter floats freely above the lens element.

Coatings

Lens coatings primarily have two functions. One is to increase lens contrast, the other is to keep your filters clean. Early photographic multi-coatings increased color rendering and overall contrast in an image. Modern-day multi-coatings improve upon this by adding benefits like anti-static, water repellent, and oil repellent coatings. These coatings can help keep your filter clean, which in turn, prevents image quality degradation caused by dirt and dust gathering on the lens.

While many modern-day camera lenses have these coatings already applied, budget lens filters do not, which is a reason why one might see an increase in image quality when these filters are removed. By adding a filter without these coatings, you are essentially canceling out the benefits provided by the native lens coatings already applied to your lens.

Does it matter if I get a UV vs. Protective filter?

For the most part, no. On a digital camera, these filters will perform nearly identically, as sensors already block IR and UV light. A UV filter will, however, give you clearer pictures on a 35mm image by correcting UV hazing in a photo.

That said, some UV filters- primarily cheap ones- remove some visible wavelengths along with IR and UV. This could have an effect on color, albeit a nearly imperceptible one.

Can a filter really protect your lens?

Yes. There have been multiple times throughout my photographic career where a lens has been protected by a filter. Additionally, filters prevent damage to one of the most important parts of your lens, the front element. This lens is often coated, and these coatings can be worn down over time from exposure to the elements and repeated cleanings. Lenses that exhibit “cleaning markings” typically lose a portion of their value compared to those with pristine lens elements.

Additionally, lens manufacturers such as Canon recommend using a protective filter to fully weather seal a lens. Without a filter, some lenses that claim to be dust and water-resistant lose their protective traits.

So what filters do I use now, knowing this?

Right now I have two primary types of protective filters on my lenses.

Marumi EXUS Lens Protect SOLID Filters & Breakthrough UV X4 Filters.

I originally discovered the Marumi filters when reading Roger Cicala’s extensive posts on UV filters, over on the Lensrentals blog. They performed very well and struck the right balance between quality and cost.
I originally purchased The Breakthrough UV X4 filters from my local camera store, as they were the only new filters kept in stock. These are well designed and are marketed as a premium product, which makes them feel like the “Apple” of the lens filter world. 

All in all, I prefer the Marumi filters, due in part to better reflection rate, and better protective qualities. Marumi claims in their filters are 7 times stronger than conventional filters. Breakthrough filters use SCHOTT glass, which should be structurally harder than glass, however, I’ve broken a few of these filters now while having never broken a single Marumi filter.

UV filters are strangely divisive. Many photographers are adamantly anti-filter, while others can’t imagine going without them. I myself believe them to be a valuable investment, and that you should always consider quality when picking out your lens filter. Don’t invest thousands of dollars into a professional-grade lens, only to put a cheap filter on the front, as you will negate all the engineering that went into your lenses’ native coating while sacrificing image quality. If you aren’t sure which filter to get, consider checking out my preferred brand Marumi or visit Lensrental’s blog where Roger Cicala has conducted extensive testing on many popular brands.

Have questions about filters or lenses? Drop a comment down below, or visit my contact form to reach out.