Tuesday, 16 August 2011

The Forth Bridges

If you are unfortunate/dim-witted enough to also follow my twitter feed, you may have seen a message yesterday which combined a popular Christmas ditty with news of a neutral density filter. You probably wondered what I was going on about and promptly unsubscribed. Here is a link to resubscribe, re-follow, re-gret..... 

So what is a neutral density filter anyway? It is a filter which doesn't really do anything other than reduce the amount of light hitting the sensor, ie no colour casts, no warming, no chilling, no polarising, or at least that is the theory. Bored yet? You will be. They come in several different strengths, measured in stops of light. One stop, two stops, six stops, ten stops. A one stop will look a bit grey. A two stop version also grey, but darker, and so on. Like sunglasses I suppose. A ten stop one looks black, you can barely see through it. Supposedly used to photograph people welding and so on, industrial forging. Yawn. A far better use is to be able to create long exposures in broad daylight without burning out. In the normal course of things, even if you set your aperture to something really tiny like f22, and reduced your ISO to the lowest it will go, any long exposure measured in seconds is going to allow so much light to hit the sensor that you will get an almost totally white image. Every wondered how people do those chocolate box waterfall pics where the water is all creamy and soft? I reckon they use very strong neutral density filters. I have no idea how the maths works, and I have yet to find a waterfall, but supposedly a ten stop ND filter reduces the light throughput by 1000x. You can happily have a thirty second exposure at midday, and this is the oneI went for.

I decided to try it out on the Firth of Forth Bridges, the theory being that the bridges would stay still, and that the Firth would go all creamy. In position, filter on, I had a look through the viewfinder to compose the shot. Ah, first issue encountered. Black. I took off the filter so I could actually see what I was taking, and then flipped the lens to manual focus (I think of everything!) and put the filter back on. Click. Would it work?

Well, it does, and there is a huge amount of potential, but I think it is going to take a lot of work to have a successful chocolate box-illustrating career. It is basically trial and error as to what happens, almost entirely guesswork with the camera in manual mode, fiddling with different apertures and shutter speeds. If I head up to the hills, I will try and find a suitable waterfall, but for now, the sea will have to do. What I can say it that it is jolly good fun, very much like this blog post. Ahem.


  1. I actually do find this interesting! The photos are really good, too

  2. The second one in particular is stunning.

  3. I agree. The second one tops it. Be good to give it a go with a Dipper somewhere with fast-flowing water, or some coastal waders.

  4. Really nice shots!

    Just enough detail on the technical front and not boring at all.