Long Exposure Photography with Neutral Density Filters

For 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 for the most is smoothing out water, but it works great for creating dramatic blurred clouds and adding a sense of movement to any scene.

You can also use these techniques for photographing static subjects where you want to blur out people walking around, as well as getting wide apertures for shallow depth of field in bright conditions, although for this a lighter ND filter would be fine.

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 just isn’t going to be enough! I would recommend if you want real effect, going straight in for a 10 stop filter, which are a bit more specialist and expensive but worth the investment. On the same 1/250 example you would now be getting a 4s exposure and usually you can tighten the aperture, drop the ISO and get a good 20-30s from this in daylight.

You can always stack filters, before I got my 10 stop ND I used two ND8 filters to get 6 stops, however this is more hassle and likely to introduce vignetting on wider lenses.

There are a few 10 stop filters on the market varying in price and quality, 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. The Lee Big Stopper and B&W 110 are two of the most popular, but have a read of the link below.

http://www.the-digital-picture.com/Reviews/10-Stop-Neutral-Density-Filter.aspx

Having read this I did a bit more investigation and found no more complaints on the Hoya Pro ND 1000 ghosting effect mentioned here. As it seemed an excellent performer in all other aspects and 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 and would happily recommend it.

Using the Filter

There are a few key things you will really need to think about when shooting 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. I would recommend taking the shot without the filter a couple of times to get the composition right without having a long wait each time.
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 without the filter. Get your focus set on auto or manual, then make sure to be on manual focus before putting the filter on, be careful not to knock the focus ring at this point. You can always check focus in live view afterwards with the magnified focal point which is handy.
3. Exposure time – I would normally shoot in aperture priority but sometimes manual works best. Your camera should work out the shutter speed by itself in Av mode, 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. You will need a remote shutter release for BULB mode to keep the shutter open with no movement of the camera.
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. Try to avoid really windy days as you’ll struggle to keep the camera steady even on a good tripod over 30+ seconds.

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! Small differences in exposure time can really change the feel of the image, for instance a longer exposure on the 30s sea groyne photo at the top of this post would have completely removed the texture from the water.

You want some movement in the shot to make a long exposure worthwhile, this is often water or clouds, and you can choose to either smooth these right out for a minimalist look, or keep a level of detail there to show some dramatic movement.

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