Time lapse Photography - Concept & Techniques

This technique is effectively an automatic version of stop motion video, which

shoots at a very low but constant frame rate. This technique is used to encapsulate large span of time in few seconds or minutes. Instead of shooting studio-based

models it is usually used to capture organic motion or natural phenomena.

Individual frames are recorded, at pretty normal exposures, but with large

intervals in between. The interval could be anything from a few seconds to

hours or even days. The concept is to rapidly speed up events otherwise

impossible to easily observe, such as a flower growing, blooming, wilting and

finally withering, or clouds rapidly speeding by, or the erection of a large building.

Sometimes the event can be orchestrated, as in the assembly of a large

construction, other times it may be completely uncontrollable, such as the

building of a bird’s nest.

Although simple in concept and straightforward in theory, timelapse can

involve some very complex planning. Firstly the timing of the shot must be

determined. Here there are two major considerations, the time the event being

recorded will take to complete and the screen time production would like it to fill.

Imagine a shot for Euro TV (25 fps) that must last 4 seconds on screen; it will

require 100 frames. The time for the event should then be divided by this shot

length to estimate the interval between frames. Thus for a plant which has a life

cycle of 25 days we should allow a quarter of a day (6 hours) between each

frame. This is a nice simple example because our plant is being grown in a

greenhouse which is constantly illuminated for the shot. The exposure could be

a normal 1/50 second at whatever stop although this would then create a very

jerky, steppy result. If a smoother, more flowing and graceful movement is

required then perhaps some motion blur should be introduced. This could be

done in post-production (preferable) but it could also be achieved with a long

exposure time achieved by slow film, small aperture and heavy neutral density

filtering (obviously low light would not be good for the plant’s growth).

However, if our shot was of a building being erected and it took say 100 days

to build then that would mean we would expose just one image per day. Over

three months the quality and quantity of light is going to change appreciably and

therefore a number of extra decisions shall need to be made. Will exposure be

varied or kept constant? If the latter, then the image could take on a shimmering

effect as it varies in brightness from frame to frame. But if the former then it

should be done by varying exposure time, since changing aperture could affect

the look of the shot and it might appear to ‘breathe’. The exposure could be

adjusted by shutter angle, neutral density filtering or exposure time. All of these

could work but involve other decisions depending on the equipment being used

and the shooting method adopted (will the camera be attended or completely

on auto?). Having made these decisions it is necessary to decide at what part

of the day it shall be shot: at the same time each day – which will result in the

light appearing to move across the shot, which can be a very nice effect with

shadows smoothly wiping across the frame; alternatively it could be calculated

to offset the exposure by a daily increment so as to maintain a light level (for

example by going half an hour after sunrise).

Other technical issues must also be resolved such as whether a high shutter

speed or long exposure time serves the shot best, whether to use any filtration

at all and what film speed and color temperature to use (is the shot day or

night, dusk or dawn?).

But above all there is also the complexity of camera placement, lens length

and framing. If you are shooting a hole in the ground where a building will eventually

appear it will be necessary to decide on how to cover the two radically different

extremes – the empty start and filled up end. So, is the camera locked off

(most timelapse shots are) and therefore how much room must be left in the top

of frame for the building to grow into? This obviously must be calculated with reference

to the architect and builders. Alternatively, will the camera be tighter and

pan up with the building as it grows. This is very tricky to work out so that a

smooth pan will be created. The pan can be made manually by each day tilting

up the camera by a predetermined amount previously marked-up on the camera

head. The camera could also be motor driven and controlled by either a

computer or special mechanism designed for the purpose. Alternatively, it is

shot on a wide locked off angle and the frame enlarged to permit movement

within it.

Apart from photographic issues, placement and organization of the shot will

also have to be dealt with. Where and how can the camera be mounted to gain

access to the required image? Will a specially built tower have to be constructed

or can the equipment be mounted on an existing structure? What is its exposure

to the elements and therefore will it have to be in a sealed weatherproof housing

with temperature and/or humidity control? Is easy access possible and, if on film,

can reel changes be avoided or, if required, then a system capable of allowing

such changes without moving anything will be necessary. If video is being

used, will the recording media be at the camera head or at some more hospitable

location nearby and more easily accessible?

Finally special arrangements may be necessary for the site operation. In

the example above, for instance, with just one frame per day, people would pop

on and off in single frames which might not be acceptable. Therefore it might

be necessary to agree a certain time each day when the site would be clear –

obviously this might predetermine the time of exposure to be in the middle of a

meal break or other convenient time.

Timelapse, whether on a large scale, such as depicting a building site, or a

small scale, such as recording the life cycle of a chrysalis, can be tackled

using a variety of formats and techniques. The most convenient is a film camera

controlled by an intervalometer – a specialist control box which manages

the variables such as interval between exposures, camera shutter and pulldown.

The intervalometer needs to be used in association with a stop frame

motor. Most rental companies have suitable models for the camera types they

supply.

Video is more of a problem since unlike film the tape cannot be left in contact

with the heads for long periods. Thus it is necessary to edit in the single frame

recorded at each cue point. To avoid errors such as tape dropout it is customary

to record a number of frames for each exposure. Other decisions also need to

be made depending on the circumstances of the shot, such as whether to shut

down the system between exposures or to leave it in standby and whether the

recorder should be at the camera head or remote.

Apart from some DV camcorders which have a built in intervalometer function

most cameras and recorders cannot be programmed to do this. Thus a custom

controller or computer with special control software will be required to

govern the process. A far better approach is to record on to hard disk and for

this option a number of editing programs (such as Adobe Premiere) include the

necessary control functions and a far superior integrated approach. In cases

where the total event time is short – less than 2 hours – then it may be simplest

to leave the system recording at normal speed for the duration and then extract

the necessary frames during post-production.

It is also possible to use still cameras loaded with large magazines. These

can be controlled by an intervalometer and offer the advantage of a much larger

frame. Conversely they will have to be transferred to a digital system for assembly

into a sequence of matching frames. Registration is not always all it might be

in stills cameras although specialist units are available at a ‘price’. The advantage

of a larger frame for TV use is that a locked off shot can be made and then

with appropriate enlargement a move can be added afterwards.

Timelapse can be used for a vast array of subjects to produce both photorealistic

sequences such as we have discussed or for surreal or abstract imagery

by shooting natural phenomena such as clouds and water or specially created

subjects such as growing crystals or other chemical reactions.