Wouldn’t it be great to freeze time at the exact moment to see a rain drop create splash? Every day little things like this surround us and most of the time we don’t even realize, most of the time because they happen at such a high speed we can’t see them.
We decided to rig up a sensor that would detect the exact moment when the drop created the splash. We pointed a laser light at a Light Dependent Resistor so that it would read its maximum value. As soon as the drop would cut the beam, the LDR would read a different value and that would trigger the picture. But the problem is, it happens at such a high speed, the camera’s shutter didn’t have time to operate. To fix that we did the experiment in a dark room, and set the camera in “bulb” mode, which means the shutter opens as long as the button is pressed. Then it was a case of rigging it up to the flashes and we had it.
The procedure was: lights off, camera on, FLASH!, camera off, lights on, WOW!
We did the same for the balloon by setting up a microphone that would pick up the peak when the balloon popped, triggering the picture.
We had a great time, made a real mess but definitely ended up with some really cool pictures!
Here I leave you the video of how we did it. I hope you'll enjoy it!
wow, that's kind of eerie! I just did the exact same thing about a month ago, with milk and a pair of scissors to get the camera to focus on the right spot. Very cool!
However:-
LDRs are very slow and so there is an added delay built in. Better use a photo transistor or photo diode.
I did this last year with a laser and LDR. I had to introduce a delay so it was timed properly - the speed of the LDR didn't hamper it at all. What did hamper it was having to get the autofocus-only camera to focus, arm the flash, turn the light off, arm the arduino and drop the thing all in a rather cramped bathroom (the only windowless room I have).
Just for reference, you can do freeze-motion quite effectively without the room being totally dark.. it needs to be dim, mind you, but remember the exposure is going to be done by the FLASH, not your shutter. You also don't want to have depth-of-field issues, so you are going to use a small aperture (large f number), which will limit the amount of light. If you are using a xenon strobe, the background dim lighting useful for setting things up is not consequential to the actual shot. I typically use Bulb for stop motion shots, with the shutter open for seconds.. but the strobe is of course only a thousandth of a second long. It's a matter of light energy..
You'll be interested in a project I have waiting in the wings: I've been collecting the flash units from disposable cameras, and will be building a special-effects strobe with variable triggering for multi-stop freeze framing. Right now I have six strobe units, but plan for the project to use a total of ten of them, with additional triggering for several external studio or slave flashes. I don't recommend this kind of thing to kids or anything... ANY camera flash contains HV Capacitors which RETAIN CHARGE EVEN WITH NO POWER- and can be DEADLY. (sorry, just important to mention that kind of thing!!!)
Most of us photographers here build camera/flash triggers as first projects.. it's a great way to get into the whole thing, the projects tend to be simple, and the results can be impressive. You should also build a sound trigger, I've had a lot of fun shooting wine glasses full of flourescent dye under blacklight and xmas tree bulbs, strobe triggered by the sound of the BB gun firing. You've got 90% done, now just start playing with other sensors..
Very cool!