On our last post we saw what high speed triggers are available, on this post we will build our first trigger and and take the very first high speed photo.
I started doing high-speed photography after being wowed by images I saw on the Filckr. Images made by hobbyists like me. As a very experimental (purely for fun) activity, I wasn’t about to commit large amounts of money to it.
Turns out to be tremendous fun, so over the time since I started in the summer of 2008 I have have “upgraded” my triggers in that I have encased the experimental circuits in plastic boxes and fitted 3.5mm jack sockets and proper case-mounted controls – ie with proper knobs and switches – to make them more portable and more robust.
Totally over the top really, and an unnecessary expense – the cases, sockets and switches cost 3 times as much as the parts inside! Still, once I had discovered what a great game this was, it seemed worth the time and effort to break out the ancient soldering iron and commit the circuits on prototyping boards (aka breadboards) to soldered stripboard, cased.
I’m slightly ashamed to say that my first delay circuit is still on a breadboard stuck down inside the box. I know, I know… outrageously lax but it has been used lots, carried around to flickr meets etc., and it still works just fine!
Your First Trigger – Sound Trigger
All the circuits are courtesy of the helpful people at HiViz.com – you can source your own components if you like, but I was quite unsure about what I was doing then so I bought their kit of parts. This is what came: Not too scary, is it!
This is what I built in less than half an hour, following the instructions on the hiviz site
The “RF-04” device is the transmitter of my original (2008) wireless flash trigger – it normally fits on the camera hot shoe, but by connecting the ouput of the sound trigger (3.5mm jack plug on the right) to it I can fire the flash remotely. If you don’t mind wires, that jack plug can be replaced by a hot-shoe adapter, say, for the flash to sit on. Or maybe a PC connector if your flash has the appropriate socket. It would just need a much longer lead
The cheapo method of adjusting the delay between sound-pickup and flash-firing is to move the sound trigger further away from the sound source – such as a bursting balloon or a pistol firing. For the optical gate, move the infra-red beam nearer to or further from event to be captured. The best method is a digital timer between the sound trigger and the flash, allowing for accurate and repeatable settings. The middle way (yes, you guessed – my way) is a simple and inexpensive analogue-controlled delay circuit like the HiViz one.
The set of pictuers below documents the build
(1) The optical gate as a set of parts
(2) The working optical gate on the breadboard
(3) The delay unit parts
and (4) the final, working photo-gate + delay circuit in its box.
The final picture (5) is the finished product ready to go. It looks far more complicated when boxed [picture 4] because of all the wires connecting the knobs, switches, and sockets!
Note that in the final picture, the output of the circuits is plugged into a wireless shutter release instead of the wireless flash trigger used above. It works with either, but the slow events that I was using the optical gate for (cherry drop!) allowed me to fire the camera shutter, and I put the wireless flash transmitter on the camera in the normal way – so the camera fires the flash units.
The First Shot – The Egg Sacrifice
For these high impact – and much higher speed – events, the latency in my wireless shutter release – and even the inherent shutter lag, even though tiny in a dslr, say – makes it desirable to fire the flash directly from the trigger circuitry. So this time, the camera is left with the shutter open throughout the “event” and the flashes are connected directly to the ouput of the delay circuit. Also, the impacter (in my case a crossbow) is fast, so that a short delay is needed. The delay circuit is switched to a range of 0 to 0.1 seconds to give finer control. A range of 0 to 0.01 seconds also works, but only with the crossbow pretty close to the target.
A second problem is that to capture these faster events, the flash duration needs to be as short as possible – set at 1/128th power – and that means not much light. You can use higher ISO and a large aperture, but if you have access to multiple flashes life will be a lot easier! Two flashes at 1/128th give as much light as one at 1/64th (ie one whole stop better) but keeping the all-important very short duration. Even when I started in 2008, old flash units could be picked up on eBay for £10 (gbp) or so! That’s why I have three ancient Vivitar 283’s – boosting the light output but keeping the short flash**.
The crossbow makes a nice solid “thump” when it is fired, so a sound trigger works well here. Just as before, a few test shots are required to set the delay so that the bolt appears exactly where the target will be. Actually, it’s slightly quicker to get the bolt in frame and then put the target right there! These pictures are from a collaborative shoot with two interested members of my local flickr group (the Hull pool) – they will appear again later!
The shot here is quite repeatable. A slightly longer delay will see the arrow pictured to the right, a slightly shorter delay will see the arrow further left, as shown in this sequence:
As soon as the position and exposure are set, it’s time to put in the target and take the shot!
How Accurate Can/Should I be?
These analogue controls don’t give a delay measured in an exact number of milliseconds, but the fine control is outstanding – as shown here:
The type of target determines the effectiveness of the shots:
Now, how fun was that? On our next post we will build a better trigger and drop some cherries – prepare for photogate.
** A note of warning about using old flashes: two of these Vivitars are the oldest sort with high sync voltages. That means they work as normal, firing when the hotshoe terminals are connected, but the two pins are presented with around 250v by the flash unit’s circuitry. That was fine for old mechanical film cameras, but feeding that voltage into modern electronics is not good. In fact, it’s bad! It will fry most cameras and flash triggers, so special care is needed with them… I used a couple of “peanut” slaves (optical triggers) so one (low sync-voltage) flash connected to the event trigger – the delay unit in fact – is fired, and the flash from that immediately fires the other two. The time taken is of the same order as the flash itself, so it does work! More recently, a friend upgraded his flash triggers, so I bought his old ones – CT301’s – because they can “take the heat” from the old Vivitars and suffer no harm.
The prices of the old flashes have rocketed up now, so they cost about the same as a new YN 460 (for example). Now that the inexpensive (kind of) YN etc flashes are available, maybe the old stuff will become less salable and therefore cheaper again!
About The Author
Brian Davies is a photographer and a Retired educationalist based in Hull, UK. You can follow his flickr stream here.