Tag Archives: flash

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.
04/8/14

Making of "Captivity"

In this one, I wanted to create an mood similar to a jail by projecting the light through something like “metal bars”.
I used a cutter and cardboard to create my bars and set a flash behind it on the right of the camera to project the shadows of the bars onto the composition.

I could have created shadows with a more defined borders by placing the flash farther from the cardboard, so that the relative size of the flash would be smaller, but for me it was ok this way, because it can be interpreted as an office curtain too, which I also found appropiate.

To emphasize the highlights and textures of my hand and give the impression that the person was in tension and sweating, I used a dropper with water to wet my hand. I used an old keyboard I had at home because by combining it with the b/w processing seemed more adequate to me than a modern keyboard.

Before:

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After:

04/3/14

Making of "Drowning"

To create this photo, I used my computer screen again as a softbox. I wanted to get the silhouette of the glass so I didn’t need a flash, and using a tripod I could choose the dof I wanted and then the necessary exposure time to get a white background.
I placed the razor blade very carefully before filling the glass until it held in the position I wanted, and then I started to fill the glass with water using a dropper, and also doing some photos of the composition while I was filling it, just in case the razor blade changed its position, in which case I could loose the shot.

Also, in the first attempts I noticed that the edges of the glass weren’t as defined as I wanted due to unwanted light coming from the screen, so I placed a couple of books as flags to reduce the amount of light on the sides of the glass to get a more defined silhouette.

Finally, I used photoshop to create the silhouette of a face and then its symmetry with a copy of the layer.

Before:

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After: