Long exposure photography has become very popular in the last couple of years, getting a lot of coverage in landscape photography magazines and on photo sharing websites.
With the ever-increasing number of options for 10-stop neutral density (ND) filters on the market, there has never been a better time to give it a go.
However, taking photographs when using such high-density filters gives rise to a set of problems that you may not have previously considered, so this article is intended to give a few useful tips that I have picked up since starting my journey learning about long exposure photography.
First, a bit of Background…
A neutral density filter should be just that: neutral; blocking out light without leaving a colour cast on the resulting image. Each ‘stop’ of an ND filter reduces the amount of light entering the camera by a factor of 2, i.e.:
- 1 stop = 21 = 2 = ND2
- 2 stops = 22 = 2 x 2 = 4 = ND4
- 3 stops = 23 = 2 x 2 x 2 = 8 = ND8
- 4 stops = 24 = 2 x 2 x 2 x 2 = 16 = ND16
- 10 stops = 210 = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 1024 = ND1024
A fairly common 2-stop filter (often referred to as ‘ND4’) reduces the amount of light hitting the sensor by a factor of 4. A 3-stop (‘ND8’) filter by a factor of 8 and so on, until you get to 10-stops, when the light is being reduced by a factor of 1024, meaning that the shutter needs to be open for over 1000x longer than without the filter.
Whilst this is the reason that you get silky smooth water or clouds rushing across the sky, it is also the reason why your workflow will need to be adapted to overcome issues as a result of the huge reduction in light.
On to the Long Exposure Photography Tips…
Tip 1: Whilst a tripod is considered a baseline requirement for many landscape photographers, it is even more important when shooting with a 10-stop filter. Exposures can easily extend to greater than a couple of minutes, so it is vital that your tripod is as sturdy as can be. This typically means ensuring that the legs are stood on firm ground, the centre column is not extended and the strap is secured so not to catch the wind.
You will often read that people recommend hanging your camera bag from the tripod to add ballast weight, however I think that it can often act as a large sail and cause greater instability if windy, so I instead tend to place a beanbag (full of uncooked rice) on top of the camera to add extra weight, without significant additional surface area.