Monday, 5 July 2010

No. 1 London Bridge (again)



This was shot with a Canon 5D MkII, and the Canon 28-70mm f/3.5-4.5 I wrote about in an earlier post. For stills photography it's a decent lens, limited by poor border quality at wider apertures; the fact of having to stop down to f/8, f/11 restricts you to shooting in good light outdoors, and limits your options for fill-in flash indoors.

As a video lens it comes into its own. Video is forgiving of lenses because the resolution is relatively low, and you can get away with much lower shutter speeds, because the stuff you're shooting is moving anyway. f/11 isn't so limiting at 1/30th or 1/60th of a second. As a consequence the 28-70mm f/3.5-4.5 makes for a decent video lens, especially given that it is small and light. It's long out of production and is only available on the used market.

The 5D MkII is still available new although it's a couple of years old now. For guerrilla filmmaking the 5D's only major limitation is the size and weight, which means that you'll need a relatively hefty tripod or support. I used a Gorillapod SLR Zoom, which is the second-heftiest model the company makes and will support 3kg, which is almost as much as a human head. It's solid enough to hold the camera pointing straight upwards, albeit that the 28-70mm f/3.5-4.5 is a featherweight. It would probably struggle with the old 28-70mm f/2.8 or any of Canon's L-series zooms. If you have e.g. a Canon 550D or Nikon D5000, for example, a standard Gorillapod SLR would be more appropriate. Having said that, the standard model only holds 800g; it's a shame they don't sell a 1.3kg model. In my experience the Gorillapod's ball head is a godsend, and the flexible legs are a kind of bonus that I rarely use, but on those occasions when I need them, I have them.

For ultimate guerrilla filmmaking then something like an Olympus E-P1 with in-body stabilisation and the Panasonic GH1's range of video capture options would be the ne plus ultra, the sine qua non, the crème de la crème. It would be der musikant, mit Taschenrechner in der Hand. It would be like Holly Hunter in Miss Firecracker, small and easily portable, and good-looking. The E-P1 will go places that the 5D cannot go, because the E-P1 is a gentleman's camera, whereas the 5D is a brute.

Wanna grow / up to be / be a deshaker
The film is made out of long, five-minute video sequences sped up with VirtualDub, rather than a series of still frames. Even with support, it was a windy day and the raw footage was often a bit shaky. Furthermore, some of the shots were taken on London Bridge, which wobbles when buses go by. No amount of tripod will steady London Bridge, but fortunately there is a piece of software that will do this. It's called Deshaker and it's awesome, and just like VirtualDub it's free. I surmise all this free software was originally developed so that people could pirate home DVDs; now it powers me.

Here's what it does. The first fifteen seconds are raw and unprocessed. Notice the wobble every time a bus goes by. The second and final fifteen seconds have been run through Deshaker. They still wobble, but not so much:



It's not so apparent at this smaller size, but look at the area of background behind the YouTube logo at about 10-11 seconds in, and then fast-foward to 25 seconds to see the same snapshot de-shook. I don't have the space and time to tell you how to use Deshaker. It is nightmarishly complicated, although the brief instructions on the website work fine (you select "pass one", play the video, then select "pass two" and do your compression and filters etc and output the results). Every time I have fiddled with the options I have made the output worse.

I also did the music. Lots of M-Tron. I don't know how to write about music.

PROTIP: Earlier on I mentioned shutter speeds. Traditional Hollywood-style motion picture cameras typically shot at 1/60th, which is very slow for stills photography, but not a problem for a movie. Although the individual frames of a movie shot at 1/60th might have motion blur, the movie itself appears to have a liquid flow of motion when played back. The effect emulates the continuous flow of vision experienced by the human vision system. And it emulates the continuous flow of life itself.

In the modern era of video cameras and digital capture it is much easier to use a fast shutter speed, which produces an oddly "hyper real" look, with each individual frame captured in perfect clarity. When played back, a movie shot with a higher shutter speed looks like a series of still images one after the other. The effect is jarring. Steven Spielberg famously used the effect in the battle sequences of Saving Private Ryan, in order to express the chaos and random clarity of warfare. It's commonly used in sports and news footage, so that people can run through individual frames, but the effect becomes tiring after a while. The clarity is too much. Also, it evokes the sweating, ugly faces of rugby players. Rather than e.g. Terence Malick's Days of Heaven.

The jerky hyper-reality was long a problem with stop motion photography, and animators historically devised numerous methods of introducing fake motion blur, culminating in Industrial Light and Magic's motorised "Go Motion" effect. There's an interesting pair of articles in the Skeptical Inquirer, from 1995, about this very topic (one, two).

I digress. The point is that video shot at 1/60th or slower looks more fluid than video shot at higher shutter speeds. In daylight this is a problem, because even shooting at ISO 100, f/11, with a polarising filter, I had to use shutter speeds of 1/125th or thereabouts. I needed to use a neutral density filter. Or a cloud. There's a good overview of this topic here, on a blog about the Micro Four Third standard. It has little Lego men going around in a circle.