Tag Archives: water

09/21/14

Low cost laser barrier Photography

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After trying to capture an exploding water balloon with a very rudimentary method (see here), I dedided to try again but using a low cost laser barrier and a LDR (Light-dependent Resistor) to get more accurate results.

Materials:

  • 1 Laser diode (5v, a pack of 10 is very cheap on eBay).
  • 5v Power supply (or 4xAA batteries) for powering the laser.
  • 1 small LDR (Light-dependant Resistor)
  • 100K variable resistor
  • N3 camera connector (Canon 5D) or minijack depending on camera model.
  • Bag of water balloons
  • Also a flash is necessary to freeze the motion, and also using it at the minimum power possible.

Circuit:
 
Knowing that to shoot the camera with an external cable we need to short-circuit two wires (Shutter and Ground), I put a 100K variable resistor between the two wires and saw that the camera shoot when I set the resistance lower than 25K.
Once we know that resistance, we know that if the sum of the variable resistor + LDR is < 25K, the camera will shoot.
To build the circuit I just put the LDR and the variable resistor in serial and then connected them to the shutter and ground cables of the camera. The variable resistor serves to callibrate the initial status and set the camera to a point that almost shoots. Then, when we point the laser to the LDR, its resistance lowers and the overall resistance between the Shutter and Ground cables will be < 25k, so the camera will shoot. In normal conditions, when the water balloon is in front of the LDR, the camera won’t shoot because the LDR resistance is too high to trigger the camera. When the water balloon explodes, the laser beam will illuminate the LDR.

Camera and flash settings:

  •  Shutter: 1/125 (if there’s ambient light it should be faster).
  •  Lens focus set to manual.
  •  ISO 400
  • Apperture: f/8-f/12 to get enough DOF.
  • Flash power set to 1/64 and zoom at 105, about 60cm from the water balloon (on the left). Also, the flash is triggered from a remote emitter in the camera.

Once all is prepared, we just have to tie a water ballon to the rope so that it is placed between the laser and the LDR, and when we make the balloon explode with a needle the camera will automatically shoot.

Original idea:

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Setup and circuit:

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Results:

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Notes:

  • I built the same circuit with a LDR of a greater size and it didn’t work so well, so I recommend using a LDR of the same size as the laser point if possible.
  • I noticed a significant delay between the balloon exploding and the camera shooting, which I didn’t find so slow in my old Canon 40D. To solve this I recommend setting the water balloon higher than the camera frame, so that the balloon doesn’t appear in the frame until the water balloon falls.
02/24/13

DIY Water Balloon Photography Tutorial

One of the interesting techniques I hadn’t still tried until now was to capture an exploding water balloon just in the moment the plastic breaks, but the water still has the shape of a balloon. I didn’t want to invest any money in laser barriers or something similar, so I built a very simple mechanism that wouldn’t give me the perfect timing but maybe an acceptable approach.

Materials I used:

  • 2 sewing needles
  • A pice of plastic of about 20cm of length to build the lever.
  • 3 meter camera cable (for ease, depending on camera position)
  • A plastic washbowl
  • A small flash with wireless remote
  • A bag of small water balloons
  • A hot glue gun if possible (or just glue)
  • A tripod to hold the mechanism and water balloon, and another to hold the camera.
  • A mop!

Camera and flash settings:

  • Shutter of 1/100 or similar is enough, because we’ll illuminate the water balloon with the small flash only.
  • I recommend using an apperture of f/8 or narrower, because sometimes water goes in many directions and this way we’ll get more dof.
  • For the tests the flash was at 0.5m approx, at 1/64 of power. I recommend using the lowest power if possible to get a more sharp result.
  • Camera focus must be set to manual and I also recommend to adjust the frame for each photo since the size of the water balloons is not always the same.

Shutter trigger construction:

About the shutter trigger, my Canon 5D MKII uses an N3 connector, so I cut an old shutter cable to build the new one. It has three wires (Ground, Shutter, Focus) that will allow us to make a photo by doing a short circuit between Shutter and Ground wires. I’ve marked with a green dot the two necessary pins in the photo of the N3 connector. It’s not necessary to use the Focus wire since the camera will be in manual focus.

To build the other side of the wire, I welded each wire (Shutter, Ground) to a needle. Then I used the hot glue gun to attach the needles to a long piece of plastic with a little inclination so that if the needles touch a rigid surface they will touch each other. My initial idea was that the water of the balloon would short circuit the two wires, but at practice it didn’t result in my case, so with a little inclination in the needles they also touched each other when breaking the water balloon.

To hold the lever I used the materials I had at home, but it’s possible to hold it in many other (and better) ways.

Once the setup is mounted, a water balloon is hold with a string in front of the lever so that when the lever is released it will break the balloon and the needles will also touch each other to activate the camera shutter and make the photo, so the only thing we have to do is hold the lever in a higher position and release it to make each photo.

Photos of the parts and results:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Video of the mechanism in action:

As you can see the results are quite different between each other, because the timing was a little unpredictable. There are a lot of ways to improve this first test, trying to anticipate the explosion by placing the shutter cables in another place in the lever or changing the way the wires touch each other.

Opinions and questions welcomed 😉