Collecting Images for Time-Lapse Videos

Collecting images for a time-lapse video is straightforward and very similar to the method of creating images for star trails described in Chapter 22. The basis for the technique is to acquire images at set, repeated intervals, as shown in Table 14.1. Of course, this interval needs to be equal to or longer than the shutter speed! Methods for creating the sequential exposures include repeated manual exposures (not recommended!), using the in-camera intervalometer and using an external intervalometer, as described in more detail in Chapter 22.

Once the composition and interval are set, the camera settings are adjusted and the exposures started, there is little to do other than sit back, relax, and enjoy the scene unfolding before your eyes! There are a couple of things that you will want to confirm before you start the sequence; let’s go through those now.

The importance of having a stable, locked down tripod can’t be overestimated. Even a minor shift of position midway through the collection of a nightscape sequence can effectively ruin it. As always, it is imperative to confirm that the tripod legs are fastened securely in position, and that all of the knobs and fixtures are as tight as possible. Hanging a heavy bag from the bottom of the tripod’s post to add inertia is always a good idea, especially if there are even light to moderate winds, Figure 14.1. I often carry a sturdy fabric bag to fill with rocks for just this purpose. I also carry carabiners clipped to my camera bag for the same purpose, Figure14.1. If your tripod doesn’t have a hook at the bottom of the central post from which to hang such weights, they can often be purchased as an accessory. It is not recommended to drape a bag or other weight over the entire tripod, as doing so will generate an inwardly directed force on the tripod legs. This force may cause unwanted shifts in position of the tripod legs during the night.

14.1 (a) Hanging your camera bag or other heavy object, such as a fabric or plastic bag filled with rocks or sand, can add much-needed stability to your tripod. While important for single images, the requirement for absolute stability is even greater during the many hours needed to create images used for time-lapse videos. (b) Carabiners make it easy to attach and remove your weights from your tripod.

Camera power is also an important issue to consider, since it is unlikely that a single battery will have enough charge to operate your camera for the entire duration of your image collection sequence. If your camera allows the use of an external power supply, and if this is a feasible option, then this is the way to go. Some cameras have modified battery packs available that can be inserted into the normal position for the battery and then attached to an external power source. Alternatively, an external battery grip is a very useful addition, Figure 14.2, since it can significantly prolong the time-lapse duration. Also, for some camera models, e.g. Nikon, the battery in the grip can be changed throughout the shoot without affecting the overall position or movement of the camera. When doing so, the primary battery inside the camera’s main compartment continues to operate the camera.

14.2 An external battery grip can greatly extend the shooting duration, critical for time-lapse image creation. In addition, the battery within this Nikon grip can be swapped-out, mid-shoot, further extending the shooting time. This is possible provided the battery in the camera’s main compartment retains enough power to keep the camera operating during the battery swap.

Many nightscape videos are created with essentially the same exposure settings of the camera, although one or more adjustments in exposure time or ISO might be required. As described in Chapter 22, such sequences are readily converted into a video with only minor post-processing in Lightroom. Such time lapses include motion of the Milky Way across the sky, the flickering lights of the aurora, or billowing clouds of the pre-sunset hour.

“Holy Grail” Time-Lapse Videos

Nightscape time-lapse videos that begin before sunset and continue all the way through civil, nautical, and astronomical twilights into full darkness (and the same in reverse for sunrise) experience an enormous range of exposure values (EVs); often over twenty EV! This range is far beyond the capabilities of any camera to collect correctly exposed images with a single set of exposure settings. Instead, the operator is forced to change the exposure settings of the camera significantly, multiple times, during the collection of the sequence. The many abrupt changes in exposure in images made immediately before and after such changes in camera settings can become highly distracting in the final time-lapse video unless steps are taken to mitigate their effects. The difficulty in doing so has led to these types of nightscape videos being dubbed the “Holy Grail” of time lapses.

One method for performing these adjustments, as described in detail in Chapter 22, is with the LRTimelapse software. This powerful program makes it straightforward to smoothly adjust the exposures of all the images in the holy grail sequence to produce a single, pleasing video, from pre-sunset all the way through to complete darkness.

Adding Motion to Time-Lapse Images

The ultimate feature in time-lapse video creation involves steady movement of the camera during image collection. The result is a heightened sense of drama and discovery in the final production. The downside is a substantial increase in complexity, power requirements, and transport logistics. Also, the images resulting from a time lapse with motion cannot be combined later into a star-trail image.

Panning is the main type of movement during nightscape time-lapse video production. It can be accomplished by moving the camera along a straight rail held up at either end by supports, or by slowly rotating the camera about that head of a fixed tripod. One relatively inexpensive way to accomplish panning is with the Polarie head, Figure 14.3. Designed for equatorial tracking during long exposure images of the night sky, Chapter 22, it makes an excellent mount for slowly panning across the scene during the collection of images intended for a time-lapse video.

14.3 Here, the Polarie Star Tracker Mount is used as a panning head. Its slow rotation provides a steady, rotating motion, highly suitable to adding movement during time-lapse image creation.