That Shouldn’t Have Worked…

Mountain stream at Graenfjall, Iceland
Camera: Canon EOS 7D | Lens: EF-S17-85mm f/4-5.6 IS USM | Date: 26-08-2011 16:21 | ISO: 100 | Exp. bias: 0 EV | Exp. Time: 1/5s | Aperture: 14.0 | Focal Length: 26.0mm (~42.1mm) | Location: Grænafjall | State/Province: South | See map | Lens: Canon EF-S 17-85mm f4-5.6 IS USM

There’s a lovely moment in the film Sahara where Pitt and Giordano are following a typically desperate plan in the hope that if they can kill the villain his men will just surrender and lay down their arms. When, to their surprise, this starts to happen they look at each other and say simultaneously “That shouldn’t have worked…”. This is the photographic equivalent.

There are two schools of thought on how you should photograph moving water. One approach is to use a fast shutter speed and “freeze” the motion. I’m convinced that this is the best approach for large waterfalls, fast rivers or large waves, and you’ll see it in many of my photographs. As long as there’s enough light then there’s no major technical challenge with that approach.

The opposing school of thought is that you use a very slow shutter speed (typically a large fraction of 1s) and show the water as a blur. This expresses the direction of motion, but personally I don’t think it expresses the force or the dynamics so well. However, as Iceland has almost as many waterfalls as Venice has gondolas (see “Waterfalls, Waterfalls…”) I decided that this was an ideal opportunity to experiment.

I’ve come to the conclusion that the slow shutter speed approach does work, but it works best for small features with complex flow patterns, but relatively low flow speed/force. I’ve also reached the conclusion that a lazy man will work harder to avoid work than to actually do the job! :)

Here’s the official, recommended method to get a shot like the above:

  1. Pre-visualise the result you want, ideally using a cardboard rectangle instead of actually looking through your camera’s viewfinder.
  2. Set up your tripod. The heavier this is the better. If the waterfall is a long way from the road be grateful for the exercise. :)
  3. Curse when you realise that to position the tripod correctly either it, or you, are going to get very wet.
  4. Turn off image stabilisation, and mount your camera on the tripod. Attach the remote release.
  5. Fine tune the camera and tripod position to get the composition right. Curse when more of your kit gets wet.
  6. Set the exposure to get a shutter speed of 1/4 to 1s. Start by selecting the lowest ISO and a small aperture (say f22). If this isn’t enough, attach a polariser. If this is still not enough, take out the Lee/Cokin filter kit, mount up the filter holder, and slide in your neutral density filter(s).
  7. Meter carefully. Typically the highlights will be very bright if there’s any direct sunlight, and automatic metering may either over-expose or under-expose depending on how much of the scene is bright water relative to the rest.
  8. Take the shot.

In fairness, this method works well, even if your photography costs $10 a shot and you don’t see the results until six weeks after leaving the location. However, here is the alternative Andrew Johnston Patent Digital Method:

  1. Wander over to the interesting waterfall, and decide that this is one you want to photograph with blurred movement.
  2. Realise that it’s a long walk back to the jeep, and you can’t be ****d to get your tripod. Anyway, where you want to stand it would only get wet…
  3. Set your camera to its lowest ISO, aperture priority and a high aperture. On an APS-C DSLR you probably don’t want to go much higher than f16 as diffraction effects start to kick in.
  4. Make sure image stabilisation is on. If you want to control reflections and highlights attach a polariser and get it set right.
  5. Take a quick shot to check exposure. Dial in exposure compensation as required.
  6. If the resulting shutter speed is in the region of 1/10s – 1/4s you’re probably OK. If it’s too low, just reduce the aperture. If it’s still too high, take the ND filter out of the filter pack.
  7. Realise that the Cokin filter holder is in your other camera bag, which is in the jeep. See point 2. So don’t worry about the holder.
  8. Hold your camera firmly in your right hand. Hold the filter in the left hand, in front of the lens.
  9. Fine tune the composition, breathe in, and take the shot. Check the sharpness of the static elements on the LCD. If they are sharp enough then you’re done, if not go to step 8 and try again.

OK, if I’d had my Cokin filter holder in my bag I would have screwed it onto the front of the lens, which would at least have allowed me to brace my camera with both hands. What’s interesting is that Image Stabilisation technology is good enough that you can get decent hand-held shots at this shutter speed, and immediate digital review allows you to check their sharpness.

Next week – how to induce temporary paralysis so you can hand-hold for 25s for fireworks!

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