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Variable Neutral Density Filter

Updated on December 30, 2011

Variable Neutral Density Filters are one of my favorite new photography tools. Just like a traditional Neutral Density (ND) filter these filters let you restrict the amount of light entering your lens, which is important if you are shooting on a bright sunny day or looking to have an extra long exposure. But, as the name implies, a 'Variable' Neutral Density Filter lets you block differing amounts of light.

Before Variable Neutral Density filters came along you had to carry around a number of different grade ND Filters which each blocked out a specific amount of light. However, a single Variable ND filter can replace an entire set of old Neutral Density Filters.

More Flexibility and Control

Variable ND Filters give you more than just convenience and a lighter camera bag. With a set of old ND filters you can only block out light at specific steps, while a new Variable ND filter lets you block out light at amounts in between these steps. This is like using a camera that lets you only set the aperture at each of the f-stops versus one that lets you set the aperture at each 1/3 of an f-stop.

How Do They Work?

Variable Neutral Density filters are circular glass filters which consist of two lenses, a back lens which is fixed and a front lens which can be rotated. As you rotate the front lens the alignment between the two lenses changes blocking more or less light.

Make Your Own Variable ND Filter

You can see the same effect by staking two polarizing filters on top of each other rotating one of the lenses.

While this trick can work in a pinch, it is not very practical as you will get vignetting around the edges of your photograph from stacking the two filters.


As with all filters it is important to get the highest quality that your budget can afford. It makes no sense to put a cheap filter on an expensive lens as your optics are only as good as its weakest link.

This is no different when purchasing a Variable Neutral Density Filter. Lower quality Variable ND filters will not evenly block light throughout the light spectrum. This result in photographs with a particular color tint to them, which will get worse when the amount of light blocked is increased. With a cheaper Variable Density filter photos taken with minimal light blocked may be fine, but ones taken closer to the maximum may be unusable.

Here you can see the color tint caused by a cheap filter.
Here you can see the color tint caused by a cheap filter.


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    • TrahnTheMan profile image

      TrahnTheMan 5 years ago from Asia, Oceania & between

      Thanks aperturering, that's really helpful, sound advice. I'm interested in a variable ND for video work mostly (as you would know, when shooting video you really want to maintain your shutter at 1/50-1/60 (a 180 degree shutter) to retain a 'filmic' look, and also want the wide apertures for depth of field, meaning you have to have ND to adjust for brightness. And I'll stop searching eBay for "step-DOWN rings"! Cheers.

    • aperturering profile image

      aperturering 5 years ago from Raleigh, NC

      Thanks Trahn. I have been using the Fader ND Variable Filter. The color stays true on it until it and then quickly drops off after several stops. I have not tried out the Multistop filter from Formatt. You generally get what you pay for with the ND and those lens do appear to be in the right price range, but I would try and find someone who has one to see how they do at the higher stops.

      You should expect to pay between $100 - $200 for a good variable ND filter, maybe a littler higher if your getting a really large filter like an 82mm. Your really wasting money if you buy one of the cheaper ones as the pictures they will produce will be noticeably poor quality.

      If you have multiple lenses you can get a single filter the size of the largest lens you will be using it on. Then, you can use it on your other lenses by attaching it with a step-up ring, which cost a couple bucks each. Step-down rings would be for going from a larger lens to a smaller filter and are seldom a good idea as they will cause vignetting.

      Keep in mind, if you have any extra long telephoto lenses you wont have to worry about getting a monster filter to fit it. With telephoto you generally want all the light you can get, so it's seldom you would use an ND Filter on it.

    • TrahnTheMan profile image

      TrahnTheMan 5 years ago from Asia, Oceania & between

      Nice overview. Have you used the Formatt variable ND? What do you use? Also, given different lenses have different thread sizes, is it possible to get a larger filter that can adapt via a step-down ring to a smaller lens?

    • Huntgoddess profile image

      Huntgoddess 5 years ago from Midwest U.S.A.

      This is very good to know. Thanks for the information, and pictures. All I really have access to right now is the cheap disposable cameras. Always wanted to have better equipment, but have no idea what it's all about. Glad to have some intro here --- and on your other Hubs.

      DzyMsLizzy --- your dad sounds like a great guy. So glad you are following in his well-trod footsteps.

      Sometimes folks claim that Photoshop can fix many disasters anyway. But, I don't really trust that way of thinking.

    • DzyMsLizzy profile image

      Liz Elias 5 years ago from Oakley, CA

      Ah, the latest and greatest! I'm all in favor of a lighter camera bag--my old beast must weigh nearly 20 pounds with all the add-ons I the tripod!

      I got my love of photography from my dad, who even built his own darkroom. I fondly remember him gamely tramping along assorted hiking trails when we were camping, his still camera bag with his twin-lens-reflex camera on one shoulder; the 8mm movie camera bag slung on the other. I used to tease him about resembling a pack horse.

      Then I turned around and got an even bigger bag! HA! He who laughs last....

      Voted up, interesting and useful.