The perils of using an ND filter.

Wreck, Cefn Sidan, Carmarthenshire (1/15th second at f16)

In October last year (see this post) I wrote about using a ten-stop neutral density filter at a rather surreal stretch of coastline near Aberdaron on the Llyn Peninsula. As waves came in I used exposures of several seconds to create blur and fizz from water moving amongst rather sculptural black boulders. I don’t claim for one moment that this was a new idea of mine, but I was happy to get good results from a technique that others had been using for quite some time. In fact, this kind of result has been possible since the very earliest days of photography. At first it was inevitable given the very limited sensitivity of the materials then available; there was no choice but to use long exposures. More recently apertures of f64 were possible with the large format film cameras used by certain landscape photograpers, with long exposures the inevitable result.  There are several examples in Paul Wakefield’s first book “Wales – the First Place” , published in 1982. Some photographers would use twilight only or even moonlight to obtain the same effect. But this technique really wasn’t mainstream.

Same subject, 10 stop ND filter, 2 secs, f11

Then I noticed a trend. Photographers were asking online about where to get hold of neutral density filters. For over a century and a half one of the main advances in camera technology was to make it possible to stop movement. And now people wanted to do just the opposite.  I just couldn’t understand it. I suppose I’m just a bit slow on the uptake, because images using ND filters were suddenly to be seen all over the internet.  Typically they would feature a coastal structure such as a pier surrounded by waves rendered silky and smooth by the use of a long exposure. And usually at sunset. A ten-stop filter was often used, which cut down the amount of light reaching the sensor to one thousandth of that actually available.  Lee Filters coined the term “Big Stopper” to describe theirs, while some cheapskates used glass from welding goggles as an economical substitute (….. ok, I tried that …..). Some photographs were actually very effective, but there were a much larger number of copycat images produced by the less imaginative.

Skokholm Island ; ND filter 5 secs @f11

I do now use a neutral density filter occasionally, but not necessarily when one might expect to.  An ND filter can bring an extra element of interest into a daylight seascape, for example in the image of Skokholm on the left, as well as at dusk. But there are times when I have reached for one, used it and then regretted it. Look at the main picture here. The sand snaking away from the camera in the wind is an integral part of the image, but too long an exposure removes it almost completely. Over a period of two seconds the sand particles are never in the same place for long enough to register on the sensor. Fortunately I saw the error of my ways before leaving the scene, removed the filter and had another go without it. In the previous post (click here) I described another example of NOT using an ND filter when others might have used one – in fact, were doing.

I always advise against using an ND filter to photograph waterfalls, too. I have to admit that I am a sucker for a silky waterfall shot, while others loathe them. In reality there is no correct way of making a still image of moving water, and it is down to personal preference in the end. But choose your day (cloudy, even light is ideal), use a narrow aperture (eg f16) , and a polariser, and you will easily be able to achieve an exposure of about 1/2 second – which in my opinion is just about ideal for a waterfall. An ND filter is almost never required.

So there we have it. Sometimes a little bit of subject movement will make or enhance an image , but an ND filter may remove it.  Use one at your peril!

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Repeat until it gets dark……

Porth Ysgo (recent)

In summer 2011 I discovered Porth Ysgo, a tiny cove near Aberdaron at the tip of the Lleyn peninsula. I was working on Wales at Waters Edge, my book about the Welsh coastline. It took me a while but eventually I noticed that the beach was littered with extraordinary rocks. It wasn’t so much their shape – although there were some interesting ones – but their colour; when wet they were pitch black. I used a heavy ND filter to slow down the wave motion and create a frothy foam which contrasted strongly with the solidity of the rocks. One picture appeared in the book and I vowed that one day I would go back.

Porth Ysgo (from Wales at Waters Edge)

Well it took more than six years but I finally made a return visit last week. I met up with my old friend Brian Boothby, a very fine musician and photographer, and it was with a growing sense of excitement that I descended the steep steps down to the beach. Conditions were just about right – a receding tide with a fresh onshore wind.  On this occasion I didn’t mind the cloud cover. I put the camera on the tripod immediately, fitted the ND filter and started shooting long exposures. I very rarely use it otherwise but live-view is brilliant in this situation. It gives an “actual exposure” simulation while the image in the viewfinder is virtually invisible thanks to the heavy filtration.  It all went well for a while until I noticed that I was getting some massively under-exposed images. I checked all the settings but still no joy. Then I realised what the problem was. Having set a two-second self timer to prevent camera shake, I then took my eye away from the viewfinder. Light entering the viewfinder during an exposure of several seconds was affecting the automatic meter reading by about two stops. In other words, it was cutting the exposure to something like a quarter of the correct one. It seems odd that this should be possible. Can someone explain it?

So the solution was simple. Once you have found your location and accepted that it is usually pot luck with long exposures, this type of image is actually quite easy to create:

Use live-view to compose the image.  Set the self-timer. Wait until a likely looking wave begins to enter the frame. Place the thumb over the viewfinder. Press the shutter. Repeat until it gets dark.

In fact, Brian had been exploring and found another tiny cove nearby with more extraordinary black rocks.  This time they were larger, more sculptural, and placed randomly on the shore, almost like surreal chess pieces. There were also some massive square-ish blocks, each the size of a small car, piled on top of each other well above the waterline. But salt spray was filling the air.  I managed a few more long exposures, then began to enjoy the sheer exhilaration of the conditions as darkness began to fall. Who needs photography on an evening like this?

Edit: but it’s always nice to come back with a trophy or two………

 

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