Using ND Filters for Long Exposure Photography

So as my first blog post I decided to cover a technique I have been using more and more recently, which is using heavy neutral density filters to create long exposure photographs, even in bright daylight conditions.

The thing I use this the most for is smoothing out water, but it also works great for creating dramatic blurred clouds, removing people from shots and adding a sense of movement to any scene.

Choosing a Filter

When looking at buying a filter, the first consideration is how dark to go. The most common ones are fairly light, ND2, ND4, ND8 for example. Even an ND8 only blocks out 3 stops of light, meaning a 1/250 shutter speed would still be 1/30, which isn’t going to blur anything! I would recommend if you want real effect, going straight in for 10 stop filter, which are a bit more specialist and expensive, but have a serious effect. On the same 1/250 example you would now be getting a 4s exposure.

There are a few of the 10 stop filters on the market, I would recommend having a good read through some reviews as some have issues with colour casting and vignetting which will give you a little extra work at processing.

Hoya Pro ND 1000 67mm

This is a very thorough review, using some good testing procedure. That said, having read this I did a bit more investigation and found no more complaints on the Hoya ghosting effect mentioned here and as it seemed an excellent performer in all other aspects for a good price I picked one up in 67mm for my Tamron 17-50mm f2.8. I bought this from London Camera Exchange for £64.

Using the Filter

There isn’t anything hugely technical to learn here and the main thing is to find subjects to shoot and give it a go.

There a few problems you will find when going to really long exposures with a filter like this.

  1. Composing – your viewfinder isn’t much use with this filter on, you can either compose in advance, lock off your tripod and then fit the filter, or use live view to show the scene with the filter on.
  2. Autofocus – the camera can’t see much more than you can so autofocus won’t really work, again the best way is to set this up first while composing, then switch to manual focus before putting the filter on, make sure not to knock the focus ring at this point.
  3. Exposure time – this your camera should work out by itself, but there’s a good chance you’ll go over 30 seconds on some occasions and need to use the BULB setting, get an app or find a lookup table to calculate exposure time, for each stop you need to double the time.
  4. Movement – do everything you can to reduce movement when using long exposures, so use a good sturdy tripod and head, either a remote shutter release or short self timer and set your camera to mirror lock up so there is no vibration when the shutter opens.

Don’t always assume shots will look better with this technique, it’s easy to get carried away, but I would always recommend while you’re there taking the same photo with a few different shutter speeds including one without the filter. This isn’t something you can add, edit or remove in processing like a lot of other techniques, so you need to make sure to get it right at the time!

Check out the two shots below which show the same scene, with identical processing, but with and without the ND filter.

Loch Ness 30s Exposure

Loch Ness 30s Exposure

Loch Ness 1/25 Exposure

Loch Ness 1/25 Exposure