One of the questions I often get asked when out shooting is what type of filter I'm using and why I use that neutral density photographic filters. There is a lot of information out there on the subject of photographic filters but what I hope to establish is how I use them as a landscape photographer and scenes that I think are best suited for their usage. *Note: I'm not paid by any company or corporation and all opinions are my own based on the gear that I use.
Neutral-Density Photographic Filters
I was first introduced to neutral density filters in 2007 and that's when I purchased my first filter, a 55mm 0.9 Hoya ND filter. While I anticipated this filter would be a game-changer for my photography, it was not quite what I had thought it was going to be. First, it was harder to focus the camera because at the time I was only using autofocus. The AF points struggled to find focus at times and without knowing it I had a lot of "soft" photos as a result. While neutral density filters do allow for deeper color saturation, many have what is called "color cast" and will manipulate your photos to look tinted; especially in the corners.
The more that I researched the topic of neutral density filters, the more I realized that my preference would be to use them to show motion in water and in landscapes. Because I wanted to achieve this specific look, I knew that I would need a darker filter. The first filter that I bought was suitable but not ideal, so I bit the bullet and bought a much darker filter; a 1.8 ND filter.
The difference between the 0.9 and the 1.8 is in how dark the filter is meaning that it is going to filter out more light requiring longer exposures. For the 0.9 ND filter, I found that in broad daylight I was still taking photos that were not long enough to achieve the look I wanted. I would stop down or narrow the aperture and yet I wasn't getting the silky smooth water look that I wanted. When the 1.8 filter arrived, I affectionately nicknamed it the welding mask. I couldn't see through the filter which made autofocus even more difficult, yet as I got the hang of working with the filter the results I was getting were more aligned with what I saw in my head.
In case you're wondering what the decimals mean when it comes to neutral density filters, here is a guide. The decimal corresponds to how much stops of light will be filtered, which means that you'll need a longer exposure to get the same results as you would find without a filter. The ND filter blocks light from hitting the sensor, so you'll need a longer shutter speed to overcome this.
ND2 or 0.3 - 1 stop
ND4 or 0.6 - 2 stops
ND8 or 0.9 - 3 stops
ND 16 or 1.2 - 4 stops
ND64 or 1.8 - 6 stops
ND100 or 3.0 - 10 stops
Also, refer to this article on Wikipedia about neutral density ratings.
I also have a 10 stop ND filter that I use from time to time, its usage is dictated by what I want to add motion to and how much available light there is where I'm shooting. I have found that my 1.8 or 6 stop ND filter is one of the more versitle neutral density filters out there for what I'm looking to achieve.
Example Photos Taken With Neutral Density Filters
As you can see from the examples above, I utilize photographic neutral density filters to show motion. In three of the photos, I'm taking photos of waterfalls and this is my primary usage for the neutral density filters. In the second photo, I'm using the long exposure of 30 seconds to show the movement in the clouds on a summer day. This is one of the first times I have used this effect in a landscape photo because I so rarely shoot during the middle of the day.
The best thing to remember when deciding on a neutral density filter is to remember what effect(s) you are going to be looking to achieve and then buy what suits that need. As always, if you have any questions or comments about neutral density filters or their application please ask below in the comments and I'll be happy to reply. Next time, I'll be going over graduated neutral density filters and their application.