Most likely you have been blown away by an image that has a silky and dreamy sky or river. Perhaps you have even tried to take images like this yourself but the result is nothing like what you hoped for. Maybe you’ve even understood that this effect comes as a result of using a long shutter speed but there’s no way you’re able to get the shutter speed longer than one second. The truth is that this effect is made by the use of a dark filter placed in front of the lens. Neutral Density filters have become an essential part of most photographer’s camera bag. This introduction will give you an insight in how these filters will improve your images, how to use them and most importantly what they are.
The truth is that this effect is made by the use of a dark filter placed in front of the lens. Neutral Density filters have become an essential part of most photographer’s camera bag. This introduction will give you an insight in how these filters will improve your images, how to use them and most importantly what they are.
What Are Neutral Density Filters?
Neutral Density Filters (commonly referred to as ND Filters) are filters placed in front of the lens to reduce the amount of light entering the camera. This allows the photographer to use a slow shutter speed to create motion blur and/or create a shallower depth of field.
Let’s say that you’re photographing a waterfall and want to blur/obscure the water.
A shutter speed of five seconds is required to capture the desired effect. By using a narrow aperture in dimmed light this would be achievable but the quality won’t be optimal. Also, if you’re photographing during the daytime, or even sunrise or sunset, it can be too bright to achieve such a long exposure. The solution is an ND Filter.
Since the filter is a dark piece of glass you insert in front of your lens, it reduces the amount of light entering the camera, allowing the use of a longer shutter speed.
Various Types of ND Filters
Choosing the correct ND Filter can be complicated if you’ve never looked at them before. There are numerous brands, different degrees of darkness and even different systems.
Let’s look at what options you have:
Screw-on filters are like the name indicates filters that are screwed on the front of a lens.
The benefit of using a screw-on filter is that compared to square filters less light slips through the bottom- and top edges of the filter, which means that it’s easier to calculate the correct exposure in the beginning.Personally, I don’t find this to be a problem and I normally add this factor in my calculations for finding the correct shutter speed.
The downside to this system is the challenges you face when stacking filters. This is when you use more than one filter at the same time, which is very common.
If you want to use an ND Filter to obscure movement and a Graduated ND Filter to balance the light, you will get what’s called vignetting. The edges of the filters show in the corners of the image, creating an unwanted dark frame.
Remember that you need to purchase multiple filters if you wish to use them on different lenses. Alternatively, you can purchase adapters but make sure that the filter then is big enough to use on the lens with the widest diameter.
The square filter system is quite different than screw-on filters. To use them you need an adapter and a filter holder in addition to the filters.
First, the adapter is screwed on the lens, then the filter holder is clipped onto the adapter. When this is done you can simply slide the filters into the holder.
This system makes it possible to use multiple filters at the same time, without getting as much of vignetting.
Occasionally, you might see some vignetting when using an ultra wide-angle but rarely as much as when using screw-on filters.
The differences between brands are often noticeable when comparing the square filter systems. Most brands have different ways of creating the filter holders and adapter. For example, with NiSi Filters you can place a Circular Polarizer inside the filter holder but for other brands, you need to purchase an external adapter for that purpose.
Since lenses vary in filter sizes you may need to buy more than one adapter if you plan on using the ND filters on different lenses.
Which is Best?
Finding the filter that fits best for you can be a process in itself. In the end, it depends on your needs, preferences and budget.
Prices vary depending on brand, quality and filter type. Square Filters are normally more expensive as you also need the filter holder and adapters that cost roughly the same as the filter itself. However, the filter holder is a one-time investment and most filters fit in other brands holders (be sure to look at the specifics first if you wish to combine products).
My first ND filters were some really cheap screw-on filters from Best Buy. For a beginner, these did the job and I never experienced any major problems with them. After a while, I realized that I needed something of higher quality and darker glasses (I’ll come back to degrees of strength in a minute) so I invested in B+W screw-on filters.
I used the 10 stop filter for about one year before I changed over to a square system. At the time I used LEE Filters and despite their heavy blue color cast, I was quite pleased with the quality.
Today I’m using the NiSi Filters, which I’ve become an ambassador for, and I absolutely love them. Finally, I’ve found a high-quality filter system with no color cast.
Note that some ND filters have a color cast. Certain brands handle it better than others which are something you should consider when purchasing them.
Degrees of Strength
Now comes the complicated part; the degrees of strength!
You may have heard the terms one stop, two stop or ten stop before.
These terms tell you how many stops you need to extend the shutter speed by using that filter. In other words, how much less light reaches the sensor in the same amount of time.
ND0.3 equals 1 stop less light than without the use of filters, allowing a shutter speed of twice the time.
ND3.0 equals 10 stops and 1000 times longer shutter speed. By using a 10 stop ND filter, you can change a 1/125 second shutter speed into 8 seconds.
Here is a list of the most common degrees:
- ND0.3 – 1 stop – 2x shutter
- ND0.6 – 2 stops – 4x shutter
- ND0.9 – 3 stops – 8x shutter
- ND1.8 – 6 stops – 64x shutter
- ND3.0 – 10 stops – 1000x shutter
Some brands have also started developing even darker filters that are categorized at up to 16 stops.
Neutral Density Filters in Use
Let’s look at some examples to help understand the different effects you can achieve by using Neutral Density Filters.
The shutter speed of the image above was 1.3 seconds. Getting the same amount of light without using a filter would require a 1/3 second shutter speed.
An exposure of 1/3 you would still have a little blur or motion in the water, but not enough to create the effect I wanted.
Notice that the clouds are not blurred. This is because they aren’t moving as quickly as the water and the shutter speed was not long enough to capture that motion.
On this next image from Barcelona, the water looks like ice or glass, and the clouds are dragged in a long motion over the sky. This is the result of a 245(!) seconds shutter speed.
To achieve such a long exposure during the weak light of a sunset you need a 10 stop ND filter. This means that my shutter speed would be 1/4 seconds without the filter (245/1000 = 1/4).
Taking one or two test shots is an advantage when photographing long exposures. By doing so, you know what shutter speed you need when placing the filter in front of the lens.
If you go straight for the long exposure you have to guess how long the shutter speed should be, which often results in multiple failed attempts.
Recommended Reading: Ultimate Guide to Long Exposure Photography
Hopefully, you now have a somewhat better understanding of what ND filters are and what system to use. These filters are considered essential among most landscape photographers and I do recommend that you get some too. It’s a good way to take your images to the next level.
Do you already have ND Filters? Which type do you prefer? Let us know in the comments!
If you want to learn more about Long Exposure Photography I’ve shared everything I know in my eBook The Ultimate Guide to Long Exposure Photography. This eBook is for those who are ready to take their images to the next level and expand their creative vision.