I bought my Nikon camera for the purpose of astrophotography. I’ve never taken off the UV filter it came with for fear of damaging my lens, but recently I wondered should I keep my UV filter on for astrophotography? I did some research and found the answer.
You absolutely should not use a UV filter for astrophotography. At night, they do far more harm than good. The extra layer of glass on your camera amplifies visual artifacts and lens flare. Furthermore, UV filters do a poor job at protecting your lens from damage. Using a lens hood is much better protection.
What does a UV Filter do?
UV filters were originally meant to block or absorb ultraviolet light from the sun. In the past, ultraviolet light was dangerous to your camera and lens. Today, our cameras have built-in UV filters and are only damaged by these rays in extreme amounts. Photographers now use UV filters to protect their lenses from being damaged or scratched.
Of course, there are hardly any ultraviolet rays at night because UV light comes from the sun. However, you still run the risk of damaging your lens which is why many photographers opt to keep their filters on. It also stops the risk of damaging your lens while cleaning the smudges and dust off. Cleaning a lens with liquid can be dangerous, a filter removes this danger. But UV filters aren’t as great as you might think.
What is lens flare?
Lens flare is a visual distortion in your photos caused by the scattering of light from inside your lens. Lens flare is often caused by a UV filter reflecting light back and forth in your camera. Lens flare looks like a green ghost of the highlights in your image. They usually appear in circles or hexagons, matching the shape of your aperture. Lens flare is the reason UV filters are harmful at night.
What makes astrophotography different?
But why does lens flare only occur while shooting astrophotography? If lens flare is such a problem why don’t we never use UV filters? Well, lens flare is usually only visible while shooting with a fast aperture. Because light goes in and out of your aperture lens flare takes the shape of your aperture. A faster aperture makes these shapes larger and distortions more visible. Night sky photography is usually taken with a fast aperture as well as bright street lights or a bright full moon in the photo. This is a perfect recipe for lens flare to occur and that’s the reason lens flare is only a problem at night.
What are the benefits of a UV Filter?
If there’s no ultraviolet light at night, are there any benefits to using a UV filter at all? Well yes, actually, a UV filter still protects your lens from damage that you are especially susceptible to in the dark. If you scratch the front of your lens, instead of needing to replace the lens, you only need to replace the lens filter. Replacing a lens filter is far cheaper than replacing a lens. A UV filter also stops dust from coming into contact with your lens. This increases the length of your lens’s life span. But sometimes stopping dust works a little too well.
What are the drawbacks of a UV Filter?
As I’ve mentioned earlier, a UV filter stops dust particles from reaching your lens. Unfortunately, this can often backfire. Instead of collecting on your lens, dust simply collects on your lens filter. This is still better as it prevents your lens from being damaged by the dust, but it does not solve the visual effect of dust on your lens. In many cases, it may even be amplified. Using a lens filter, although protecting your lens, may make it easier for the dust to collect. I wouldn’t abandon my lens filter for this specific reason (because it wouldn’t solve the problem), but instead, routinely clean your lens filter with a microfiber cloth.
I’ve said this before, but UV filters cause lens flare and distortions in your photo. Your filter may also shatter when dropped causing even more damage to your lens than there would’ve been if you had no filter, to begin with. This is one of the reasons using a lens hood is a better way to protect your camera than using a filter, more on that later.
Can a UV Filter cause problems during the day?
In general, a UV filter will not cause any problems during the day, and it’s actually a good idea to use one. It stops ultraviolet rays from the sun as well as protects your lens from scratches. It doesn’t cause lens flare in the day as it does at night unless your shooting at the sun. The dust particles on your filter are still an issue but it’s not one that we can solve.
What can I use instead of a UV Filter?
Instead of a UV filter to protect your camera, try a lens hood. A lens hood will effectively protect your camera if you drop it while actively fighting against lens flare and glare. If you drop your lens face-first on the ground, the front part of your lens (the part that matters) won’t get scratched. A lens hood will not shatter when dropped, unlike a filter, which often causes extra damage to your lens. A lens hood also blocks bad light from the sides – the light that contributes to visual artifacts. Although a lens hood will not stop all dust, it can stop dust from the sides and prevent them from collecting, unlike a filter. If you’re still not convinced, a lens hood usually costs half the price of a UV filter.
In conclusion, you should use a lens hood instead of a UV filter for astrophotography. A UV filter simply does more harm than good. I hope you found this advice on astrophotography helpful. Please share this article with your friends and comment on anything I’ve missed.