Earlier this year I bought a high speed camera for a work project (more about this some other time, I hope). It took me a while to source the batteries, because it seems there’s only one shop on the whole island that sells them and it’s almost impossible to get them shipped over. This happens to be a safety issue, as Li-ion batteries are prone to explode etc if mishandled, and they’re a solid no-go for air freight. Well, long story short I did find the one shop that sells them and last week started playing with the camera to get used to how it handles and iron out the details to help me plan for the work project.
For a proper test, I needed something that moved fast enough, but easily repeatable. For reasons that I’ll explain, I also wanted to be able to light the subject easily and brightly, ideally with available light. I decided to use one of my film cameras, to try to get a view of what happens to the shutter in slow motion. The most photogenic of these must be the Agfa Isolette II, that I’ve talked about before. I set up in the upstairs room, lit through a glass-panelled door by the bright afternoon sun. The high speed camera shoots at about 550fps at this resolution (720p), shown here played back at (cinema standard) 24fps. This gives a slow-down factor of about 23 times. The audio is a separately recorded activation of the shutter, slowed down by the same amount.
The high speed camera in question is from an interesting Kickstarter project by Graham Rowan. The model used is the Imagetec fsp1000 Platinum, with a Fujian 35mm f/1.7 C-mount lens. This particular model was the only one that could shoot at the required frame rate and resolution for my work project. Lessons learned in the process of this test shoot:
- The sensor used (and perhaps the subsequent amplifier) is rather noisy, even at low ISO (this was at 100). Given the sensor size this is not a huge surprise, I guess I had just gotten used to how clean full-frame DSLRs are.
- You need a lot of light to shoot high speed video. I knew this, of course. If you’re shooting at 550fps, your shutter speed is somewhat faster than 1/550s. Probably significantly faster, since you’re spending most of the time writing out to memory. Based on this practical experience, outdoor daylight shooting should not present a problem. Indoors I’ll need a really strong continuous light. I dug up and tested my dad’s old 2kW halogen cine lights, though I’m sure I’ll want to buy a cooler-running LED lighting of about the same output.
- Post-processing the frames will need some thinking and planning. There is something odd with the DNG files output by the camera, which couldn’t be read by my usual RAW processing software. In the end I installed the recommended Rawtherapee, though I found I needed the latest stable version. I’ll probably want to write some scripts to automate the post-processing, we’ll see.