Lego, the Simpsons, and Time Lapse Techniques ~ 2015-03-30

When I recently left a position building and running an IT department for over eight years my team and others chipped in to get me a truly excellent parting gift: the Lego Simpsons House. The kit originally debuted in mid-2015 and as a life-long fan of both Lego and The Simpsons this was truly thoughtful, so I decided to time lapse the build.

Time lapse photography has been a passion of mine for far less time than either Lego or The Simpsons, but it's still been several years since I really began to sink my teeth into the craft. What draws me to it is the how narrow our subjective human perception of the passage of time is — akin to the narrow slice of "visible" light in the broad electromagnetic spectrum. The imperceptibly slow changes of seemingly still elements in our world suddenly jump to life in the world of time lapse photography. Where a large composite of images can stretch photography's ability to encompass the three dimensions of space only time lapse photography can so manipulate the fourth dimension of time, and that's something worth making into a hobby.

Essential equipment

• DSLR Camera
• Tripod
• Cable release
• Variable Neutral Density Filters

I do all of my time lapse work these days with a Canon EOS 5D Mark II after graduating from a Canon EOS 30D some years back, though any DSLR camera will do. A good cable release will allow for setting automatic interval shooting, and the necessity of a tripod to keep the camera stationary for the duration of a lengthy photo shoot should be obvious. Lastly, I keep several variable neutral density (ND) filters of various sizes on hand to cut down light levels for shutter dragging (more on that technique below). For maximum flexibility I only use variable ND filters.

Everything outlined above is all that's needed to do all manner of stationary time lapse photography. For an added dynamic dimension there are (quite expensive) rigs to add motion and panning. These can also be built using microcontrollers and stepper motors, but that's out of the scope of this post.

Shoot manual and drag the shutter

First off, always shoot in manual mode when time lapsing. Aperture priority will adjust exposure times with every shot and generate an undesirable flicker effect in the final video. When shooting manually and with a cable release it's possible to add motion blur to the final video using a technique called dragging the shutter. Essentially all this entails is doing a longer exposure relative to the shot interval, so if a shot interval is once every ten seconds, doing five second exposures will generate a fluid blurring in the final video.

Doing a five second exposure, however, may be near impossible without drastically overexposing every shot. Something to cut down light levels is necessary and this is where ND filters are an essential tool in the toolbox. One can also opt for a tighter aperture (higher f-stop) and a lower ISO to cut light levels and exposure further and allow for longer exposures, but especially in daylight conditions a multi-second exposure can usually only be achieved with an ND filter. When using ND filters in bright light situations be sure to always test and examine exposures before setting a time lapse running. I've found that moderate quality variable ND filters can create uneven shadow patterns when turned up near their maximum, and this can easily be spotted in a test exposure.

Always do the exposure/sequence math

As someone who loves time lapses I find most time lapse videos to be kind of boring. As with any video drawn out stationary shots strain a viewer's attention span, as do videos shot from just a single angle. To keep time lapse videos interesting it's important to shoot several brief sequences from several angles.

For any time lapse sequence the magic number of frames is 200. Rendered to video at 24 frames/second 200 frames will generate just over 8 seconds of video. Well-produced time lapse videos tell a story of change and well-told stories have discrete elements (e.g. a beginning, middle, and end). By shooting several sequences that all end up around 8 seconds or less it's relatively easy to put together a final video that's far more engaging than a single long shot from one angle.

When setting up a sequence, to determine shot interval, consider how long the sequence will take to complete (in seconds) and divide by the magic number of 200. So, for example, a one hour sequence would break down like so:

1 hour = 60 minutes × 60 seconds = 3,600 seconds
3,600 seconds / 200 frames = 18 seconds / frame

With a shot interval of 18 seconds an exposure time of 9 seconds (half the shot interval) will yield an eye-pleasing motion blur in the final video. Selecting exposure time to dial in the right amount of motion blur also depends a lot on the subject of the time lapse. If the subject involves elements that may move in and out of the frame faster than the shot interval (e.g. a crowded scene where a person could cross the frame in less than 18 seconds) than a larger relative exposure time will yield better results. This is because with an exposure time that's half of the shot interval the camera is only exposing half the time, so half of the action will simply not be captured. For subjects that move and change much more slowly (e.g. a flower blooming) a longer exposure will be imperceptibly different from a short one, and shorter exposures are generally easier to set up.

For long dynamic sequences it becomes easier to find ways to do multiple angles. Instead of a four-hour shot from one angle of a subject consider four one-hour shots from different angles. In addition to providing more video to work with (assuming the 200 frame rule of thumb is observed) it also affords a photographer more frequent checks on how the shoot is going. Once a sequence is underway if some aspect of the setup is flawed it's very difficult to adjust gracefully without finding the interruption obvious and distracting in post-production. More sequences shot at shorter lengths create the scenario where the lessons learned in one flawed sequence can be immediately applied to the next and more of the resulting raw footage is usable.

Putting it all together

Post-processing techniques are enough for a stand-along post so I won't go too deep into that here. Suffice it to say that keeping sequences to around 200 frames, selecting exposure times proportional to shot intervals to create motion blur appropriate for the subject, and slicing up a project into multiple shot sequences to tell a story are three critical techniques in shooting time lapses that have served me well over the years.

I'll close with the final video of the Lego Simpsons House build time lapse. The project lent itself well to the three points outlined above as the kit was divided into seven sections. Each section took around 45 minutes to an hour to assemble so I generally did 10-15 second shot intervals with 5-8 second exposures. A bit of appropriate music, some dissolves, and some title frames yielded this one minute video. Enjoy!