[Tom] wanted to try his hand at high-speed photography and needed some equipment to get things rolling. Not wanting to spend a ton of money on a lighting rig or trigger mechanism, he decided to build his own. In a three part series on his blog, he details the construction and testing of his high-speed setup along with the improvements and lessons learned along the way.
His adventures started out with a small off-brand Cree LED clone and an ATiny15L that was collecting dust in his workshop. He built a simple circuit that would trigger the LED to light his subject, which in [Tom’s] case was a bowl of milk. Rather than using a motion or sound trigger, he opted to mount a small piezo to the bottom bowl, firing the LED any time a droplet hits the bowl’s surface.
The pictures he took were decent, but he knew he could get better results. He purchased a new, more powerful Cree LED, and wrote a small terminal program that allows him to tweak his flash parameters using his laptop. The results he gets now are far better – in fact, he has a whole gallery of pictures you can check out.
If you want to delve into high-speed photography as well, all of the schematics and code can be found on his blog.
Maybe it’s just me, but I find the pictures rather dark.
Still a low cost would be to use cheap flashes, maybe old flashes bought at low price. I’ve seen this done with single use camera flashes(many of them). But the project is very easily adaptable to a flash triggering.
I’d be concerned about the time it takes for the LEDs to dim after flashing. White LEDs use a phosphor coating which take a significant time to stop glowing. It may not be much, but in a dark room it can muddle the exposure. You can see the effect by using a camera flash on a CRT.
It could be largely eliminated by using RGB LEDs as white, but this is far more expensive. I’d stick with xenon flashes.
Xenon flashes max out at 1/100,000th of a second due to the latency of the xenon gas. With the right led you can get down to 1/2,000,000th. An unmodified canon 580ex will only give 1/38,000th exposure. During that time a 500fps aurgun pellet will travel 1/8 of an inch!
I have to admit I am pretty basic at photography.
I thought high speed photography is all about fast shutter speed? I mean, wouldn’t it be better to use a camera with faster shutter speed? Then you don’t even need a flash light. I saw some amazing results with some Canons with CHDK.
Digital compacts have electronic shutters so they can have as fast a shutter speed as you want (within reason) whereas DSLRs (and normal film SLRs) have a mechanical shutter that can sync only to about 1/250th of a second at the fastest.
By having a dark room and a short flash of light you are effectively getting a much shorter shutter duration so you can capture things like balloons popping etc. In this case, it makes the equipment somewhat portable.
For photos like this though it’s probably a waste time using high powered LEDs – for the price of three or four you can pick up a cheap flash gun from eBay and have bright, well exposed photos with a lot of detail in the images.
You do however lose out on the pulse length control Tom mentions and you will have to wait for the flash to recycle.
I like the piezo triggering, that’s neat.
I’ve heard of something along these lines being done for making DIY holograms.
In this case they used a flashtube triggered IR YAG laser to pump a KTP crystal and generate a brief pulse of green light.
Apparently some of the laser diodes used in fast DVD writers (cough Bluray /cough) are capable of being pulsed for very short times indeed, the trick seems to be to bias the dioe just below its lasing threshold with three crossed polarising filters to block the incoherent LED light.
IIRC the polariser trick works due to quantum mechanics, similar to the two slit experiment.
Thanks for all the interest. One advantage of using an LED as light source is that it can be fired repeatedly. I used this in some of my water drop photos where there is a “crown” with a column of water in the middle. Something I haven’t seen elsewhere.
The images really are a bit dark, this could be improved by using more LEDs for relatively little extra cost.
Tom