When people think of lens filters for video today, they’re usually thinking of an effect from a dropdown menu in an editing program. Yet, what we’re talking about here are actual physical glass filters. These go between your camera lens and the real world — actually filtering the light by letting some of it through and keeping some of it out. What it allows through and what it keeps out depends on the filter.
Filters fall into about half a dozen different categories: lens protection, light dimming, graduated, soft focus, polarizers, color filters, and special effects filters. We’ll look at some examples of each.
Lens protection: the UV or haze filter
What’s a UV filter do? In reality, I’ve never found myself thinking, “There’s just too much ultraviolet light in this shot.” UV filters are clear and one of their primary functions is to be between your lens and everything else — like your thumb or your car keys. Do you need a UV filter on your lens? No. Does it hurt to have one? No. Are there some potential benefits? Yes. Technically the lens filter should make far-off objects (really far-off objects, like mountains) seem a bit more contrasty. UV filtration can be serious business for some people. There are many different models that filter different amounts of UV light. If you’re shooting a lot of faraway things or want to give your lens extra protection, give one a try.
Light dimming: the neutral density filter
When you’re outside and you want to shoot at a wide aperture to get a shallow depth of field, there are a few things you can do. For one, you can increase your shutter speed (not usually a good option for videographers). Or, you can lower your ISO and maybe move into the shade. But what happens when it’s still too bright out?
This is, of course, the problem that Nigel Tufnel from Spinal Tap explains so well in Rob Reiner’s 1984 masterpiece “This is Spinal Tap”: “You’re on 10 on [your amplifier], you’re on 10 on your guitar, where do you go from there?” And where Spinal Tap’s amplifiers cleverly go up to eleven, videographers can use a neutral density filter to get that extra bit of darkness. Neutral density filters don’t do anything but block light; they’re just sunglasses for your camera.
Graduated lens filters
Graduated lens filters vary in density from one part of the filter to the other. So, the top may be very dark and the bottom completely clear. Still, they’re useful when you’re shooting a bright sky. The more opaque part of the filter darkens the sky without darkening things below the horizon.
If you pay close attention, you’ll see these filters frequently used in movies and television. You can tell when a graduated filter is being used because the dark portion of the screen stays in the same place when the camera moves and occasionally the tops of people’s heads get a little dark when they step in front of the horizon. Now that you know this, you can never unsee it. Sorry.
Graduated filters come in different colors, from blue for pushing the intensity of your sky colors to brown, which makes everything look like a Western.
Soft focus: diffusion filters
As video resolutions get higher and lenses are better and better, it’s possible for your video to be too sharp, in which case, a diffusion filter can help. Sometimes called “mist” filters, diffusion filters can also help make your video look like a low-contrast Instagram image. If that’s your thing. People used diffusion filters even when television was a paltry 480i. The old Star Trek famously used soft focus on every woman Captain Kirk was supposed to be looking at lovingly.
While it’s pretty obvious how neutral density filters and graduated filters work, polarizers are kind of magical. Light comes at you buzzing in all directions like a swarm of drunken bees. Polarizing lenses stop light that’s traveling in some directions (say a bee traveling left to right) but not others (say a bee traveling up or down).
IF YOU’RE GOING TO GET ONE FILTER FOR VIDEO, TRY OUT SOME CIRCULAR POLARIZERS.
The practical effect is that, when turned the right way, they can make the sky much bluer and, the real magical part, they can significantly reduce reflections — to the extent that you can do things like see-through windows that previously showed you nothing but your own reflection in. This can be very useful for shooting scenes through car windshields or showing people inside a café through the window. If you’re going to get one filter for video, try out some circular polarizers.
Color filters for video
There are all sorts of filters for changing the color of your video. There are filters that subtly balance the light to tame fluorescent or tungsten light, to filters that will make your video a little warmer or cooler, all the way down to ones that claim to let you shoot night scenes in broad daylight, so-called “day for night” (don’t do it). A lot of work that used to be done by color filters can now be completed in post-production by shooting log or RAW or by carefully setting your white balance before you start shooting.
There’s a reason your video editing software has a drop-down menu called “filters.” Doing things in post-production often gives you more options. While it’s incredibly easy to add a blue tint to your footage in post, it can be really difficult to get rid of a blue tint that you made by putting a filter over your lens when you shot your scene.
Special effects lens filters: Closeup
There are many special effects filters – many of which have been relegated to the dustbin. One type that is often particularly useful is the closeup filter. If you don’t have a macro lens but want a small subject to fill your frame, this filter will do in a pinch. They’re just magnifying glasses, often sold in a set, that allows for different levels of magnification. Better closeup filters are made of multiple glass elements to reduce distortion at the edges.
Another special effect filter that can be useful is a split diopter. Simply put, it’s a closeup filter sawed in half, which allows you to fake a very deep depth of field without dumping a lot of light on your subject.
One classic example is from Alan J. Pakula’s 1976 film “All the President’s Men.” Director of Photography Gordon Willis uses a split diopter to focus on Robert Redford in the foreground and also the group of reporters watching the television in the background. If you look carefully, you’ll see the actor just behind Redford is out of focus while the people further in the background are in focus.
Even with an arsenal of digital effects at their fingertips, the split focus filter still occasionally makes it into big-budget movies. Quentin Tarantino used it in 1992’s “Reservoir Dogs” when he didn’t have any money and then again in “The Hateful Eight” in 2015 when he certainly did.
Square filters vs. round filters
Filters come in both square and round varieties. One advantage of using square filters is that round filters typically fit only one lens. The square ones can be used with a lot of different lenses. However, you will still need a holder for each lens. It’s mostly a matter of preference and convenience. Swapping out square filters is faster than unscrewing a threaded round filter.
Storing your lens filters
Most filters come with a hard plastic case, but if you find yourself using a lot of them, consider investing in a multi-filter soft case that will be less bulky and let you find what you’re looking for more quickly.
Your mission, should you choose to accept it
Next time you’re watching television, see if you can spot places where filters may have been used. Figure out the effects that you think are useful, and try them in your own work.