Monday, February 04, 2013

A Lapse in Time

One kind of cool function on my Nikon D200 camera is something I almost never use: the built-in intervalometer. It's a setting that allows the camera to take pictures at specified intervals during a given time range. This is what people use to create time-lapse videos, and even though I tried my hand at this sort of thing last Spring I haven't really seen the need to do it again. That changed a few weeks ago, when my wife and I decided to bite the bullet and get a storm shelter installed in our garage. I thought it would be a fantastic opportunity to give the ol' intervalometer a whirl, and am fairly pleased with the results:

The video contains around 1800 pictures shot at 14-second intervals throughout the course of roughly eight hours. But this post isn't so much about the movie or the tornado shelter, but how I went about creating and editing the final video.

For starters, I knew I had a couple of issues to deal with up front. The first was the issue of power, or lack thereof. My camera battery lasts a while, but there is no way it would have done a shoot like this without losing power after an hour or two. At first I thought I would ask a coworker if I could borrow his battery pack, and he graciously consented. But shortly thereafter it hit me that even the mighty battery pack would only last three or four hours, which meant I was going to have to buy a power cord. Nikon sells one for $128, but I found an off-brand model on Amazon for about $25. If someone is doing these sorts of projects on a regular basis it would probably be wise to get the name-brand adapter since other companies can use substandard electronic components that might not be good for regular use, but for the occasional project it's probably fine.

Next up was the lens. Regular readers know I'm a huge fan of the 50mm f/1.8 lens, but it just wasn't going to cut the concrete mustard on this project since the field of view on that lens is so narrow. I wanted a wide angle of view to capture all the installing action, which meant I needed a lens that could capture most of my garage from my camera's vantage point in the far back corner.  Fortunately, another coworker had just the thing: a bare-bones no-nonsense 18-55mm kit lens.  It was ideal for this type of photo shoot for a couple reasons:

• 18mm wide angle meant it could capture as much of the garage as I needed
• 3.5 maximum aperture would be fine since the photoshoot was outside in the daytime, which meant plenty of available light
• It's not incredibly expensive, so if it got broken or cracked by a piece of flying debris I could buy a replacement without breaking the bank.

Behold, the kit lens! Sometimes it's all you need to get the job done.
With the power supply and the lens checked off my list, the only thing left to do was prepare for the photo shoot itself. I found a corner in the garage that was as far back and out of the way as possible, and spent a while playing around with various settings on the camera in order to facilitate an 8-hour shoot. Because the lighting conditions would change throughout the day I decided to let the camera control most of the exposure, but I wanted individual pictures to be clear enough to people would be able to discern what was happening. After some fiddling I arrived at the following settings:

• Lens zoomed out to 18mm, to capture as much of the garage as possible.
• Focus distance set manually to infinity. Autofocus would have been a mess, because the camera would have focused on all kinds of different things throughout the day. Manual focus ensured that every picture was focused exactly the same.
• Aperture opened to f/3.5, to let in as much light as possible given that the shoot would start before there was much daylight.
• Shutter speed set at 1/60, which would capture movement without much blur. In hindsight I could have set this a little slower, like 1/30.
• ISO set to 800. Normally I don't like going up to 800 because the D200 gets a little noisy, but I was trying to get the early morning pictures to be properly exposed.
• Matrix metering, since I needed a good overall exposure. I often use Spot metering if I want to make sure a certain point on the image (usually the focus point) is properly exposed, but Matrix metering basically looks at the entire photo when adjusting exposure rather than just one point. This would be much more useful given the nature of this photo shoot than Spot or Center-Weighted metering.

I shot in Shutter Priority mode, which meant the camera would be adjusting the aperture throughout the day in order to maintain proper exposure. That was preferable to setting one aperture and letting the camera adjust shutter speed, since I wanted to minimize blur in the photographs.
Setting the intervalometer on my Nikon D200
One other thing to consider is the interval for shooting, which involved a bit of math. The intervalometer on my D200 takes up to 999 photos per session, but I knew that would not be enough to document the entire day for a time-lapse shoot. I was also going to be at work most of the day, save for one hour when I usually come home for lunch, which meant that I could essentially break the shoot up into two four-hour sessions. At 14400 seconds per session, taking 999 pictures would mean 14.41 seconds between shots. Because of this, a 15-second interval would have been ideal, but since it was morning and I wasn't thinking clearly I set the interval for 14 seconds, which it turns out was enough to capture about 3 hours 53 minutes--just shy of four hours. Fortunately, I went home for lunch a tad early and was able to reset the intervalometer a few minutes after it hit 999 pictures, so I didn't really lose any shots. The guy doing the installation was also out dumping a load of dirt, so the shots I did miss weren't even important.

If you are setting up for your own time-lapse shoot, you might try this online time-lapse calculator. It will help you figure out which intervals to use and how many pictures to shoot given the constraints and conditions of your photo shoot.

Before I went back to work I reset the timer again, which resulted in a total of 2160 pictures taken throughout the entire day. I will be posting a tutorial of how I turned those into a 2.5-minute video in a few days, but suffice it to say it was much easier thanks to some of the innovations Apple introduced with FCPX compared to their previous offerings like Final Cut Pro 7 and Final Cut Express.