This is a common question that shows up in various forums. There is a lot of confusion on what benefits it provides vs. what hard it can cause. Let’s take a look at these somewhat controversial filters.
With film, and even the early days of digital, UV, or Ultra-Violet light could affect the image. It could create a hazy look or flatten the contrast of the scene. UV filters block UV light limiting the camera to visible light, which is a good thing. Modern digital cameras are not affected by UV light in any significant way.
So why do people buy them? Why are they recommended?
Well, that answer is “It protects the lens”. When this comment is made in photography forums, you will get two responses:
- No they don’t. They cause more problems than they help.
- You should never add extra glass in front of the lens other than a Polarizer or a Neutral Density filter. Any extra glass harms your image.
Like everything in life, there is some truth to these statements, and there are some myths.
They protect your lens
The argument here goes one of two ways. First, you will be told “No it doesn’t” and that your lens hood provides way more protection. If the filter gets broken, it can do more harm than good, trying to take a bent filter off or having broken glass scratch up your lens.
For impact damage, this is true. The thin glass of a UV filter might block a small bump, but it’s glass, it will break. Bent filter rings are difficult to remove, and broken glass can damage your front element. A plastic lens hood, which most lenses provide will provide some protection against most bumps. It may not do much for something coming straight into the lens that’s longer than the hood. But that type of impact is going to break right through your filter.
Impact isn’t the only type of issue that can create challenges for the front lens element. It does offer good protection from environmental attacks like rain, blowing sand or sea spray, rogue fingerprints, and condensation. Heading to the beach or ocean? Blowing sand and salty sea spray will get on the front-most glass it can find. Your lens has expensive coatings to defend against ghosting, glare, reflections, etc. A good sandblasting is a great way to ruin a lens. Sandblast a $40 filter? Toss it and replace it.
Most photographers will in their life experience condensation. This happens in the heat of summer when you’re camera’s in a comfortable 72º air-conditioned environment and you head out to 90º 90% humid air and you suddenly can’t see through your lens. Of course, this happens in the winter too when you’re camera is comfortably heated up in quite dry air and you head out to freezing temperatures with tons of moisture in the air. All that humidity changes from vapor to liquid on whatever surface it can find. Without a UV filter, that’s your front lens element. With a UV filter, it’s an inexpensive piece of glass. Most people try to wipe the lens clear instead of waiting for the lens to come to temperature. In either case, you have a choice, all that moisture on the lens or on the UV filter.
It hurts image quality
From a purely scientific and mathematical sense. This is 100% true. Photography purists will tell you to never ever put anything in front of the lens as built by the manufacturer unless it’s providing a purpose like a circular polarizer or neutral density filter designed to intentionally alter the image. You will be told to only use expensive UV filters that may be 50% or more of your lens cost.
This type of conversation makes it sound like UV filters are a serious hindrance to image quality (IQ). You would think it’s going to hurt your quality by 50% and you will be left with a distorted, blurry mess. In reality, every photographer has tolerances to the amount of IQ loss they will accept. The reality is it doesn’t impact IQ much at all. If a lens starts out at 100% of its maximum quality without a filter, a high-quality UV filter might give you 99.8% of that maximum IQ. The $40 filter from an online retailer might give you 98% of your maximum IQ. To the decerning eye who’s pixel-peeping and scanning the entire image might find issues. But most people won’t notice at all.
Only you can decide how much IQ loss you are willing to accept.
For this photographer, I usually do not go out of the way to buy a UV filter. If I have one on a lens I’m upgrading or if it comes with the purchase of the lens. If I’m making a trip to a known harsh environment, I will make sure to have them installed on the lenses I plan to take. I can clean sea spray off of the body of the lens but it is pretty risky to the coatings on the front lens element. I’m happy enough with the mid-range priced filters. Since I expect them to defend against harmful elements, I’d rather replace something cheap than expensive.