Light Activated Shutter Release for Canon DSLR Cameras
WARNING: I take no responsibility whatsoever if you manage to destroy your nice camera while trying to make this project. If you are worried about the risk, don't attempt it! I'm not an electrical engineer, and I don't even play one on TV. I am just a hack with a bit too much time on my hands. Most of the time I don't have a clue what the hell I am doing when I start a project. This was one of those projects! As a result, if you screw up your fancy camera, don't blame me…
A few weeks back someone posted an article on how to build a remote shutter release for Canon DSLR cameras. I've wanted one of these for a year or two but I was always too cheap to go out and buy one. As a result, I jumped on that project and made one the same day.
As chance would have it, a few days later my local camera club had a discussion on photographing water and other liquids. Well, this got me thinking…
The next day I went out and bought a photoresistor and a relay, and after a few minutes with the soldiering iron, I had built myself a light activated shutter release. I then rigged up the following "studio", and proceeded to take a few hundred photos of milk splashing in a pan filled with lots more milk.
Ok, ok… So I know that this is a blatant rip-off of Harold Edgerton's beautiful work of 50 years ago as seen here, and I also know that he achieved much better results.
But gimme a break!
He was shooting at 1/1M of a second, in a lab environment, with years and years of research to back him up! I did all this in one afternoon and evening, using my Canon 300D and a cheap flash!
How I did it:
- I started with the plans from Michael A. Covington's previous article on making a cable release for Canon EOS cameras found here.
- I then soldiered the two exposure button leads to the normally-closed poles of my relay. The relay that I used was a mini-PCB format device rated at 120vac, which was about 15 times the capability that I actually needed for the project.
- Next, I took my photoresistor and soldered it to one of the coil leads on the relay. I can't tell you the specs on this device because Maplin's (the RadioShack of the United Kingdom) doesn't print the specs on the packaging, and I forgot what I purchased. Yeah, I know, I could put it on the meter and figure it out. Unfortunately for you, this was the only portion of the project that I took care with and used heat-shrink on all the exposed connections! As a result, you should do what I did and just guess at what resistance to use. These things are cheap, so buy a few of em and use what works best.
- I then took my power source and connected one power lead to the other side of the photoresistor and the other power lead to the other side of the coil. Polarity doesn't matter here. For my power source, I used a 9vdc AC adaptor that I scrounged from something else. I wasn't worried about damaging my camera because the coil in the relay is electrically isolated from the switch. That said, if you wire up your relay incorrectly and fry your camera, don't come cryin to me!
- Next, I built a mounting rig using foam-core board with a "U" shape cut into the end. On one arm of this "U" I taped my photoresistor. On the other arm I taped a little LED flashlight pointing at the photoresistor, with a gap of about 1 inch between the two.
- Finally, I started taking pictures!
Ok, so what does this little hack do? Well, the flashlight pointed at the photoresistor allows the photoresistor to pass voltage to the coil on the relay. With the light on, the coil is energized and the normally-closed switch in the relay is held open by the electromagnet created by the energized coil. This switch will be held open until something interrupts the light hitting the photoresistor, at which point the voltage to the coil is cut and the relay's switch reverts back to it's normally-closed position. As soon as this switch closes, it triggers the camera to take a picture.
Guess what I use to interrupt the flow of light to the photoresistor? You got it! I use a droplet of milk passing through the light beam's path. I used the pen barrel to act as a funnel for the fluid that I was dripping down. This helped me with my aim and it also helped minimize the mess.
Now, one thing you should know about photoresistors. They have a little bit of slop in their activation and deactivation. As a result, I set my flashlight back far enough that it wasn't strong enough to activate the photoresistor by itself, but it was strong enough to hold it active if some other light source activated it in the first place. This little feature ended up being a good thing. When I wanted to activate the photoresistor, and thus energize the relay's coil, I held a second flashlight pointed toward the photoresistor. This was sufficient to activate the device. Then, I slowly removed the second flashlight, leaving the primary flashlight to hold the photoresistor active.
Once the milk droplet passed into the light, the photoresistor was deactivated. But when the droplet passed all the way through the light, the primary flashlight wasn't sufficient to reactivate the photoresistor on it's own. This kept the device from firing a number of repeat shots one after the next. Taking multiple shots might sound like a good idea. It isn't.
This whole process requires the flash to "freeze" the action in the photograph. Flashes take a little time to recharge and by the time they are ready for the next shot, the action is already over. As a result, if you were to take multiple shots you'd just end up with black, blurry frames after the first good exposure.
Ok, so now you understand how I trigger the exposure. There is one other thing that you need to understand. Don't focus your camera at the photoresistor. Instead, aim the camera down a bit. Personally, I found that I needed to aim the camera about 16 inches below the switch to account for the lag in the camera's electronics. Finding this sweet spot and then getting my focus correct took almost as long as building the whole setup in the first place!
As you can see from my photos, I have a lot of work to do to improve this process. Deal with it! It's 2:30am, and I'm going to bed! *smiles*
I've identified a few ways to make to whole thing work a bit better once I get about making the next revision, including using an alternative to the photoresistor that is sensitive to a laserpointer instead of a conventional flashlight. This would allow me to make my trigger as wide as I'd like. This could be a great way to take photo-finish images at a footrace or some other sporting event.
So there you have it. Have some fun taking pictures!
Oh, and one final thing… Try not to spill milk all over your camera or your living room carpet. *ARRGH!*
Jessica Bussert
Sample Photos
My First Test Shot
Before I assembled the studio rig, I wanted to make sure that my trigger was working. The easiest, non-messy way was to drop my lenscap past the flashlight. It worked!!! WOOHOO!!!
A Drop of Water
Next, I wanted to try another test with plain old water before I wasted a quart of milk. I was pleased...
Milk Droplets
So let's get out the milk...
More Milk
Here I was starting to get my focus a little tighter. My backdrop was a scrap of old, black mat board and I had to move to a clean spot with every drop because of the backsplash!
And Still More Milk!
Finally, I seemed to get the focus correct. I like how the reflected flash made those funky "shock wave" lines on the mat board.
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