Blog - Davecorbett

After playing with water-drop photos I began to want to try something different.  There are far better people at drop photos and there are countless computerized systems out there.  At some point that begins to feel more like robotics and programming than photography.

I began day-dreaming about how I could combine color and motion and capture a high-speed image.

As these ideas often do, this one hit me about 3 am.  I made some sketches and after about a week I built the paint-a-pult.

The Paint-a-pult

The design is similar to a Roman catapult.  It's powered by rubber bands to pull the paintbrush quickly up against a stop-bar.

When the brass tubes that hold the brushes hit the bar, it closes an electric circuit which starts the MIOPS Nero trigger.  The trigger then fires the Yongnuo YN560II flash after a preset interval.
Most of these photos are shot about 10-14 milliseconds after the brass tube hits the stop-bar.

Dancing Paint

These are my first few experiments with paint.  I tried various combinations of delay, paint thickness and the angle of the brush when it hits the stop bar.

Multiple colors

Here I've added a second brush or multiple colors on a single brush.

These are just kid's poster paints, but I'll be experimenting with acrylic and other paints soon.

I set up a second camera to catch the paint-a-pult in action from another angle.
Both cameras have their shutters open and they capture the strobes when triggered by the trigger mechanism in the catapult arm.

I had to hang shower curtains all around the area.  When the paintbrush bristles snap back to vertical, they spray paint in a near-perfect 180° arc.  I also had to put plastic on the ceiling.


Piercing water balloons with an X-Acto knife.

This is my simple setup to capture photos of water balloons being popped by an X-Acto knife.

I tried several methods of triggering my MIOPS Nero trigger.  I thought of using the laser-trigger mode, but worried that the laser would be visible on the metal knife.  I tried the "DIY" mode that would close an electric circuit when the knife stopped, but I kept getting double flashes for some unexplained reason.

Finally I used the sound-mode trigger.  When the metal clip on the carbon-fiber rod hits the brass tube, it makes a "thunk" sound.  I mounted the MIOPS trigger on the same piece of wood as the brass tube.  The sound of the impact travels through the wood to the trigger very well, and I could use a low sensitivity setting.  This allowed me to work in the dark without worrying about other noises triggering the flash units.

Flash unit in plastic cup

I put a Yongnuo YN560-II flash unit into the plastic cup.  The flash is set to 1/128th power which will give a pulse of light that is 1/12000th of a second long.  I also wrapped the flash unit in plastic film just in case some water splashed upwards.

I've tried wireless radio triggers with my high-speed photos, but they don't synchronize fast enough.  I made a custom flash-trigger cable by splicing 3 cables into one plug for my MIOPS trigger.  The solved my synchronization problem and has worked very well.

I attached the knife to a carbon-fiber rod with tape.  I hot-glued a brass tube to the wood cross-bar.  I used a metal clamp to stop the knife exactly where I wanted, allowing me to set how far the knife penetrated the balloon when the flash units were fired.

I used a second clip to set the knife into a "safe position" so that I could position the balloon on the plastic cup with the knife safely out of the way.

 This is my MIOPS Nero trigger, set to sound trigger mode.   When the knife falls and then is stopped by the metal clip, it makes a "Thunk" sound.  With the trigger mounted to the same piece of wood, the sound travels very effectively.

This gave me three variables to control - Depth of penetration (controlled by the position of the clip on the rod) the delay of the MIOPS trigger (mostly about 5 milliseconds) and the size of the balloon.  The last one was the most the most  difficult to control.  If I wanted to get REALLY nerdy about accuracy, I suppose I could have weighed the balloons and adjusted them to be the same.  The more water in the balloon, the taller it will be - affecting the depth of penetration of the blade.

The balloon is positioned and ready for the knife drop.

One flash is in the plastic cup under the balloon and will provide the primary illumination.  The light will pass through the balloon and take on the color of the balloon.  A second flash is positioned at a 45-degree angle to show the skin of the balloon.

Both flashes are hard-wired to the MIOPS trigger Flash port.

Here is the rig, ready to shoot.

All the action takes place in almost total darkness.  I set the camera to a 2-second exposure at F/16 at ISO 100. I shot several test-exposures to determine the best ISO/F-Stop combination.

The effective shutter-speed is the duration of the flash units.  In this case, I have the flash units set to 1/128th power which yields a 1/12,000th of a second  pulse duration.   The camera shutter is open in the dark for about 2 seconds which gives me just enough time to drop the knife.

The camera is a Canon Rebel T4i with the 55-250mm Lens.  Both Flash units are Yongnuo YN560-II.  ISO is 100 and I shot at F/16.

Cookie splash

This photo of a cookie splashing into a glass of milk was shot using my MIOPS trigger using the sound trigger function. 

I made a wire harness to hold the cookie to the square brass tubing clamped to the top rail of my rig.  I later Photoshopped out the two wires that extended up behind the top of the cookie.

Here is the CookieDropper 3000™

A larger piece of square brass tube is glued to the wooden block.  A slightly smaller square tube is inside and can slide freely.  The metal clip stops the tubing at the height I've chosen, just below the lip of the glass.

As with the water balloon series, the tube slides down and when the metal clip hits the larger tube, it makes a "thunk" sound which travels through the wood to the MIOPS sound trigger. This allows me to turn the sound sensitivity down quite a lot and I don't have to worry about extraneous sounds triggering the flashes at the wrong time.

Strawberry Splash

This was a very simple setup using the laser-trigger function of the MIOPS trigger.

I've found that the timing is most consistent when the object that is falling has some time to  fall and gain speed before breaking the laser beam.  Putting the beam too high results in unpredictable results.  In this case, the laser beam is just a few inches above the frame of the shot.

The messy aftermath

Strawberry aquarium splash

After shooting the strawberry falling into the cream, it was fairly quick and easy to reset for shooting a drop into an aquarium.

I moved the laser and MIOPS trigger up to just above the top of the aquarium.  I kept the yardstick in place as an aid to dropping the strawberry in the same position.

Not shown in this photo is the white foam-core sheet I placed behind the aquarium for a light background.

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