Find out what is a ND filter and why they are an important part of the gear of every Pro photographer.
Have you ever wondered how photographers take pictures of blurry waves and misty waterfalls? The answer is ND filters.
But what is an ND filter or neutral density filter? According to Wikipedia: an ND filter is a filter that reduces or modifies the intensity of all wavelengths or colors of light equally, giving no changes in hue of color rendition.
To put it short, using an ND filter is just like putting the sunglasses on your lenses: the sensor of your digital camera will get less light. To compensate for the darker scene, you’ll need a slower shutter speed. This means that when using ND filter a sturdy tripod is mandatory.
Even though an ND filter should not “change in hue of color rendition”, this is not always true, especially with cheap filters like Cokin. Sometimes you can correct the dominance with specific software like Photoshop, sometimes the dominance is so strong that there is nothing you can do. If you want to avoid this problem, the only solution is buying expensive filters like Lee or Singh-Ray.
Technical info: what neutral density filter to buy
There are two basic filter types or systems to choose from: the screw-in and the slide-in types.
The first is circular integrated filters with a mounting ring that screws into the front thread of a lens, and with a thread on the other end to screw other filter(s) or attach a hood. You can see an example of a ND screw-in filter on the left.
The second consists of a threaded adapter to screw into the front of a lens and a filter holder with one or several slots, were square or quadrangular optical resin filters slide-in. As you can see this configuration allows you to use several filters.
Most filter holders also allow for the use of a rotating circular polarizer.
The slot-in filters are the most used by professional photographers.
The strength of a ND filter is measured in Stops. But how much is it one stop?
A stop is a doubling or halving of the amount of light let in when taking a photo.
This means that if you are shooting at 1/1000 sec, when you use a 1 stop ND filter the correct shutter speed becomes 1/500 sec. With a 2 stops ND filter it becomes 1/250 sec, with a 3 stops 1/125 sec and so forth…
ND filters are available starting from 1 stop up to 10 stops.
Lee, one of the best and also most expensive ND filter producers, released a 6 stops ND filter called Little Stopper that is great for landscape photography.
When you should use ND filters
Why should you want to use an ND filter for your pictures? Instead of changing the aperture to reduce the amount of light in the image, you could simply add on an ND filter.
An ND filter can be the only solution if you want to:
- Blurr water motion
- Reduce the depth of field in very bright light
- Reduce the visibility of moving objects, such as people in front of a monument (have you ever wondered how photographers shot the Colosseum without people in-the frame?)
- Add motion blur to subjects
- Extended time exposures
Just to give you an example, I shot this picture with the Big Stopper, the 10 stops ND filter produced by Lee.
I wanted to blur both the waves and the clouds in this picture of the Twelve Apostles so I opted for a 10 stop ND filter. The final exposure time was 30 seconds.
Of course you won’t be using a 10 stop ND filter for all your images, but when used properly, the ND filters can help you to capture stunning images. This in turn will help you to create images that you can easily sell. An ND filter can also be used to shoot several images that you can later blend in Photoshop. To learn how to digital blend your images don’t miss this post.
Recently I had the chance of trying the ND filters of a new brand: Ray Masters Filters. I’m really impressed by their quality. They are made with resin (usually filters made with resin suffer from color casts but Ray Masters don’t have this problem). You can get them here.
If you want to learn how to take better travel pictures don’t miss this post.