High-Speed Thoughts
I’ve been having way too much fun with my new camera, and (as any regular reader knows) have posted several videos. Many more are still unedited and unuploaded (is that a word?), and even more will just sit as a collection of magnetic orientations on my hard drive because they ended up being not particularly interesting, but I don’t like throwing things out if there’s any chance they might be useful at some point.
Lessons learned, in no particular order:
Some things look interesting in slow motion, some things don’t.
Obviously, slow-moving (or nonmoving) things are a waste of a shot. If you can discern details with your eyes, slowing things down won’t help much. A fan filmed in slow-motion looks just like a fan moving at a slower setting. A medium-sized bird flying along looks a lot like a bigger bird flapping more slowly. What you need is some nonlinearity — some kind of inflection — for these situations to become interesting. A bird taking off, for instance, is a lot more interesting (to me) than one just flying along. But you often do it anyway, just to see if slowing it down reveals any details.
Some things are really frikkin’ fast, and slowing them down by a factor of 14 (30 fps to 420 fps) doesn’t really put a dent in it. The sweet spot is around 100 Hz. At 10 Hz or lower you can see what’s going on without assistance, and when you get above several hundred Hz you aren’t sampling the phenomenon often enough to truly see the detail — Nyquist’s theorem in action.
These are movies — things move
This is a no-brainer, but for someone used to taking stills, it’s a problem of adapting. Zooming in too far means that when the action happens, the target quickly moves out of frame, and it’s really hard to follow and keep the target in-frame. Zoom out too far, though, and there isn’t enough detail to make the shot worthwhile. For a regular video, I’d say pick your poison. For slow-motion, I think you can err a little on the side of zooming in, because you get more frames, and still have the chance to capture something interesting.
The flip side of this is that my motion has a smaller effect on the shot. The camera has a steady-cam setting, and any of my motion is “damped” by the frame rate. Physical jitter isn’t as annoying. I use a tripod when I can, but it’s not a must unless you need both hands for the shot itself.
Lighting is really important
Another no-brainer, but it still takes getting used to. You can’t really use a flash, and you might not realize how bright flashes are. Even though the camera films at lower resolution (and I assume this is to group pixels together to gather more light) the camera still doesn’t do as well in ambient light as a still photo. 420 fps is only about two milliseconds of exposure time, and you have to gather enough light so that noise isn’t an obstacle, which limits you. I’ve purchased a couple of LED desk lights for indoor shooting, as well as outfitting a traditional el-cheapo-desk lamp with a CFL (the fixture is limited to 60 Watts, but a 100 W-equivalent-brightness CFL draws only about 20 W). The drawback to this is that cheap desk lighting gives you a 60Hz flicker. I film near a window when I can, to get sunlight involved.
A corollary to this is that the aperture is wide open, which reduces depth-of-field. The camera has an occasional tendency to auto-focus on the wrong item, and the shot ends up being blurry. But that’s not a disaster, because …
Film is free
As with all digital photography, this is another habit one has to shake off if one is used to film and developing — the spectre of not having enough film, and letting that dictate whether you take the shot. Digital cards are cheap, and you can delete bad pictures right away if necessary. You can also decide if you want to re-shoot, (if circumstances permit) if you know that a shot was bad. If I’m doing a set-up shot with consumables, like match-lighting or balloon-busting, I prepare several samples.
Regular video isn’t all the great.
Even with the steady-cam on, there is a lot of jitter when holding the camera. I haven’t tried Rhett’s water-bottle hack to add mass, because I haven’t been in many situations where I want regular-speed video.
I do stills. My SLR does not do movies, and my compact is bad.
Presumably you want to avoid too much optical zoom for another reason: each pixel of your detector gets a smaller solid angle, and so less light. As well as bright lights, lots of white or silvery stuff to reflect the light you have is essential.