Neutral Density Filters as Vital Tool for Long Exposures
Professional landscape photographers adopt many photographic techniques to create works of art that define the norm of their predecessors. As technology and photographic accessories have improved over the decades, so too has the photographer’s technique of showcasing the environment. For instance, when practising a widely underutilised technique of long exposure photography using neutral density filters, photographers can manipulate time to their advantage. By changing shutter speed and installing these custom handmade pieces of glass in front of lenses, static images become moving pictures. The end result can be quite spectacular.
Changing Shutter Speed to Control Time
Amongst professionals, long exposure photography is growing in popularity. Having the ability to control exposure times using shutter speeds is key to this style of photography. A shutter speed is the amount of time that the light hits the imaging sensor to exposure a picture.
Shutter speeds measure in fractions of a second, like 1/1000 or whole seconds. This can get confusing however another way to explain this; most people would be more familiar with the sound of a traditional camera’s shutter ‘ker-chunk’ when the picture is taken, it’s the same thing. This noise you hear is the time it takes the camera’s mirror to rise and fall, allowing light to enter the camera to create the exposure.
Long exposure photography is generally between 1 and 30 seconds, but when utilising cable release accessories, longer times are available. There is one disadvantage of these longer exposure times and it’s called noise, or ‘digital noise’.
To explain digital noise, imagine a hi-fi speaker. If you were to turn up the volume with no music, you might hear loud ‘cracks’ or ‘pop’ sounds even though there is no music playing through the speaker. This example is almost the same with photography. With longer exposure times there is a higher chance of obtaining digital noise, which appears as an unsightly grain in the photo. To rectify this, it is essential to ensure you have ‘long exposure noise reduction’ turned on in the camera’s menu. With this setting on, after the exposure, the camera will apply an algorithm to remove the digital noise. This digital noise reduction process takes the same time it took to capture the original exposure.
Other recommended settings for long exposure include changing the file format to RAW – an uncompressed file format that retains all the details of the imaging sensor. Lowering the ISO to the lowest RAW compatible setting, generally ISO 100. The base ISO of my Nikon D810 is 64. But on some cameras like FUJIFILM mirrorless cameras, the lowest ISO is 160 (e.g. Fujifilm X-T3).
Neutral Density Filters
Without a neutral density filter (ND), long exposure photography is almost impossible. ND filters are dark in appearance as they are principally used to cut out the light (called ‘stops’) from entering the camera. These light stopping filters increase the exposure time for images, allowing photographers to record for longer when it’s brighter outdoors.
There are many brands of ND filters, but the ones I recommend are LEE filters due to their exceptional glass optical quality. I use the LEE Little Stopper, which reduces the exposure time by six stops of light and LEE’s Big Stopper, capable of 10 stops of reduction.
These European handmade rectangular filters fit in holders which rest on the outer diameter of the lens. When in position, the filter will cut out the light allowing the photographer to increase exposure time, which creates some fantastic results for long exposure photography.
One of the advantages of LEE’s filter system over traditional screw-in circular filters is their ability to stack neutral density filters together in the holder. This can be an advantage if you have an ND filter that is only capable of 2 or 3 stops of light. To obtain a more significant reduction of light, stacking two filters together would be the ideal scenario.
Calculating Shutter Speed
There is something you should know when installing an neutral density filter on your lens. All ND filters have a rating. This rating relates to the number of stops of light it will reduce the exposure to. For instance, an ND2 means the filter will halve the amount of light entering the camera. With this ND2 filter, all it means is you split the shutter speed by two, i.e. if you have a fast shutter speed of 1/1000 of a second it becomes a slower 1/500 of a second. ND filters come in a range of formats, including ND2, ND4, ND6, ND8, ND64, ND100, ND200.
With all these filters you will have to work out the new shutter speed to gain the correct exposure. As you can imagine it can be quite tiresome and brain numbing when you are out in the field. To overcome this, I would recommend using, PhotoPills to solve this conundrum. Once the app is on your phone, type in your shutter speed, and the type of ND filter you are using and PhotoPills will tell you what shutter speed to use. This app, like many out there is convenient, especially if you decide to stack neutral density filters together!
Creative Long Exposure Photography
There are endless amounts of subjects and compositions to photograph when taking long exposures. Professional landscape photographers love to use this technique when shooting a range of subjects, three of these include:
Water. Next time you are at a waterfall, by the ocean or river, mount your camera on a sturdy tripod, attach an ND filter to the front of your lens and dial in longer shutter speed. Results will vary, but what you should see from a more prolonged exposure is movement in the water. The reason, while the shutter is open any movement that occurs will become blurred. In the case of water, it will look like silk running across rocks or on the shoreline. With waterfalls, the effects are ethereal and almost dreamlike.
Wind. To portray the force of the wind, photographers often photograph landscapes with cloud or foliage elements. During long exposures clouds appear as streaks of movement in the sky, resulting in interesting textures within the photograph.
Fire. If you find yourself photographing an active volcano, flowing lava or forest fire, then long exposure can assist with depicting the movement of flames, ash or embers. Again, like clouds, anything moving in the image will portray as streaks. But what’s different here is embers can appear as moving trails of lights in the air. Stars and lightning are also a favourite light source for this type of photography.
As you have read, using neutral density filters with longer exposures can yield exceptional results. This combination is one of the many techniques that separate professionals from the amateurs. When you first start out, understanding ND filters do take time. So continue to pursue until you can master the result and in no time you will be taking award-winning photos.