Shooting water balloons with lasers

<![CDATA[DSC_8557 I recently got a TriggerTrap V1 for my birthday and I’ve been doing a few experiments with it to see what’s possible and how fast it really is. In this post I’ll focus on my attempts to shoot pictures of water balloons at the moment they burst. I settled on the TriggerTrap laser detector for this task, with the TriggerTrap on one tripod, hooked up to my Nikon D7000 on a second tripod a £3 laser pen mounted to a third tripod. This pic shows the approximate setup along with a couple of shutter lag tests: triggertrap-comp In order to get reasonable performance from my camera + TriggerTrap combo I had to choose some specific settings on the camera:

  1. Manual focus: I set the camera to auto focus, aimed it at the pre-defined drop spot, then turned it to manual to remove the focus delay
  2. High shutter speed: To capture balloons mid-burst I had to use as fast a shutter speed as possible. I settled on 1/5000 sec in the end as the best compromise I could get under fairly average lighting conditions.
  3. High ISO: At 1/5000 sec there isn’t a whole lot of light getting into the camera, so I had to ramp up the ISO a bit. I opted for Auto ISO so that I could make my own shutter speed and depth of field compromises and let the camera calcluate the third point in that triangle.

Even with those optimisations there was still a significant amount of lag introduced by the D-SLR’s mirror assembly (the lower camera bag image in the drop test above). I managed to minimise that delay by using the Mirror Lock-up feature on the D7000. This cut the delay by around 70% (the mid-air camera bag image) and, more importantly, made the delay consistent and predictable. By adjusting the height of the laser beam above the target I was able to offset the remaining camera lag consistently, leading to shots like this: DSC_8527 And this: DSC_8532 From the above shots you’ll notice a common problem – the water balloons I had at home were incredibly tough. Drop them from a great height and they’d simply wobble rather than burst. I switched to good old fashioned (air) balloons and got shots like this: DSC_8536 And this: DSC_8550 That was great, but the balloons were still heavily deformed at the moment they burst, leading to shots of spraying water that weren’t recognisable as balloons. So for my final shot I added one simple ingredient – a drawing pin (thumb tack) face up on the target spot. DSC_8557 Sometimes the simplest solutions are the best.

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