Colorful bursting water balloon (Highspeed - Arduino & Hiviz)

[pascalbovet.com]

Hello,

I'll describe you how I took the following shot:



I saw a lot of bursting water balloons on flickr (it seems as balloons are a popular highspeed subject), all looked very similar and I wanted to create something different. I haven't seen gel colored balloons before.. So here we go..

Stuff needed:
- Sound trigger (hiviz.com)
- Arduino (Arduino - HomePage)
- Water balloons (yeah, you probably need more than one )
- 2 Flashes with gels (flashzebra.com)
- Tripod
- Black linen
- A dark room where it can get messy
- Yongnuo RF602 Wireless Trigger (from ebay) *
and last but not least your cam

Preparation before the shot:
I have a hiviz sound trigger, which is attached to an arduino board. The arduino board is connected to the RF602 sender, which will trigger the flashes. The laptop is just needed as power supply for the arduino and in case I have to modify the code.The main reason for using the arduino is, that I can put a delay after the flash is triggered to ensure that the flash isn't triggering a second time.. The second reason is that the delay is adjustable with an accuracy in the range of milliseconds.. The preflash delay was set to 0ms in this setup.

For this setup I used the following approach. I'm shooting in a dark room on long exposure mode with a an aperture of about F10, during the long exposure I fire the flashes. (This will freeze the action).

I created a homemade blowgun for popping the ballon.. (I don't like it when hands or some sticks are in the picture, so best is to avoid them already in the shoot.)
As bullet I used a 4mm sphere (which is designed for bracelets. I put a needle through the hole and attached it with some tape.

Preparation for the shot:
You can find a setup picture on my flickr stream**
I placed the flashes, where I wanted them. It turned out that I get the best result, if the flashes were at 3 and 9 o'clock. The flashes were turned to 1/32 to get a short flash duration (around 1/20'000s). I cut a hole into the boxes to avoid wet flashes. I can easily turn the boxes and adjust the direction of the flashes.

I filled up the balloon with water and attached it to the broom (any scantling will do, the broom was the best thing I had) with a cord. I put the cam on manual focus and then I focus the subject (thanks to new magnified live view this is easy). Afterwards I turn of the lights and take a shot at 6 to 8 seconds, which should be totally black.. If something is reflecting you know where to place a cardboard or a blanket or something.. I sticked carton on all my windows in my basement to have a completely dark room.
When the dark image is a dark as it should be, I take a second shot with the flashes, to check whether the lighting of the main subject is okay..

Shooting time:
After the good preparation this is a no-brainer.
Press the shutter, aim, "shoot" and enjoy.

I noticed, that it is good to have so air on the top of your ballon, otherwise there will be no bang which will trigger the flashe. The flashes will trigger as soon as the water is already in the collecting tank, and thats much to late.
I did another shot with blue/mangenta gels and yesterday one with dark blue / red. The conclusion of this test is, that lighter colors will work better. If you want to shot with that colors you may have to adjust aperture, ISO or in worst case put the flash to 1/16 (which will result in a longer flash duration and more motion blur)..

Postproduction:
Just some basics. Crop, adjust levels, saturation and some sharpening.

Finally here the cam parameters:
Sony A550
SAL100M28
ISO 200 - F11 - 4s



I hope I could give you an insight in my deliberations. If you like this, you can have a look at my other highspeed shoots (for some of them you'll find a setup description on flickr.. And if not, feel free to ask )

I'm open to suggestions, constructive feedback, criticism (both, about the setup and this post, (as this is my first howto on dps)) and would like to her your comments..
If anything is not clear or you have any question, or need some detail information about the trigger / arduino, feel free to ask.

Regards
Pascal


* To Sony HVL-F42 users: The flash will not work on the trigger, when you start it up. You have to fire (somewhere I read, focussing should be enough) it once on your Sony A (there is a remote sequence which is exchanged between the cam and the flash). As soon as this is done you can use it on your trigger. I put the sleep time for my flash to 30 (or 60 min) to prevent falling asleep and resync it with my cam

**This is the setup from my bursting balloons with powdered sugar, but this one is pretty similar. The only things changed are:
The flashes are inside the top most boxes (to avoid wet flashes) and there is a collecting tank below the balloon on the floor.

[derekspacelewis]

Was lookin at your shots and loved how this water balloon is different than any other one. Great job and keep up the good work.

[White Spirit]

I just wanna ask a question
Why do this in a dark room??
Thanks

[pascalbovet.com]

Originally Posted by White Spirit

I just wanna ask a question
Why do this in a dark room??
Thanks

Thanks for the question..

There are several reason for shooting in a dark room:
- The flash duration at 1/16 or 1/32 is about 1/10000s - 1/20000s.. The shutter speed of your cam cant go that fast, so you would need a constant light source (see next point)
- If you're not using flashes with Highspeed sync or something similar (these flashes are much more expensive than used flashes), the sync speed of your cam is at about 1/160s to 1/250 (if you're lucky)..
=> Higher shutter speed / longer flash duration means more motion blur!
- According to different users, it is not easy to fire the cam at the right moment.. Maybe it takes to long from the fire impulse until the shutter release and you'll not get a constant result, as the time between sending the fire impulse and the shutter release can differ from shot to shot.. This may be just some ms but it could be enough..
(F.ex if the burst of the balloon takes 100ms until its over then its crap when the time until the shutter is released takes 200ms).. I've not tested this statement yet, I'll do this once..

So, with all these points it really seems to be the best solution, to have the cam in bulb mode with an aperture, that no ambient light is visible on the shot (without firing the flashes) and freeze the motion with the the flash duration..


Pascal

[terratrekking]

Great how-to.

Would you mind sharing your arduino source code?

Thank you for sharing :-)

[NgaiHill]

What a great shot, and thanks for the detailed how to. Photos on Flickr are awesome too.
Thanks for sharing.

[mattjordan]

Simply awesome shots, I have to get a few items so I can try these out myself.

Thanks

[pascalbovet.com]

Originally Posted by terratrekking

Great how-to.

Would you mind sharing your arduino source code?

Thank you for sharing :-)

Thanks for your comments..

I will look for the sourcecode.. Not sure whether I have exactly that one, but they are very easy:
- "Read the sensor"
- If (sensor value > some value ) then "fire flash"

I'll share the sourceode..

[pascalbovet.com]

Sorry for not replying earlier..

You may find the source code I use for the sound trigger / light barrier in this post:
Highspeed photography 101 - Lesson 7 | pascalbovet.com

Pascal

[stella7d]

Wow, that looks like a pretty cool experiment!!