A Time Lapse Primer
by Wayne Goldwyn, SOC
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In
the following article, time lapse director of photography Wayne
Goldwyn offers insight
into many of the
practical and technical considerations involved in planning
a successful
time lapse shot. Wayne's body of work stretches over two
decades. Recently, he provided thematic shots for director
Oliver Stone
in "Natural Born Killers" and "Nixon," two motion pictures
that effectively use accelerated time passage in a symbolic
rather than a literal sense, rendering a sense of universality
to the surreal. Such is the power of these images.
Clouds skitter across the sky. Darkness descends.
Lights flicker on. Traffic streaks red and white. The moon slides
across the sky like a white hockey puck on black ice. It sinks
behind a purple horizon and, suddenly, it is dawn. Few motion
picture effects startle or captivate the eyes as much as time
lapse photography. The compression of years, days, or hours into
seconds. The life of a flower in the blink of an eye.
SETTING THE IRIS
It is a good idea to scout the location on
a day prior to the planned shoot. Take along a light meter and
determine the proper iris setting for the climax, or most beautiful
part of the event. For example if you plan to shoot the sun setting
over the ocean you will want to start rolling film two or three
hours before dusk and will want to have the iris set so that
the reds, oranges, purples and blues of sunset are exposed at
full color saturation. Even though each new sunset may be different
from the last and some may even be disappointing with respect
to cloud formations and color, you will get the best results
by setting the lens for the moment before the sun sinks below
the horizon. You will need to start rolling a couple of hours
early so that there will be some lead-in to the shot when it
is projected at 24 fps. In time lapse photography, hours or days
can be transformed into seconds when projected at normal speeds.
Normally you will shoot at a frame rate that will equal a few
seconds of projection time for each hour of shooting. Therefore,
by rolling off 50 to 120 frames of film prior to the climax of
the shot you will have from two to five seconds of lead-in time,
or a "handle," that will be needed for editing and optical transitions.
To achieve the best image be sure to choose
the proper film and shutter speed. For example, 5245 (ASA 50)
is the most flexible for daytime time lapse shots. Most time
lapse motors turn the shutter at speeds slower than the customary
1/50th of a second used in 24 fps photography. Typically, the
time lapse shutter will turn at 1/15th of a second. As a result,
for day shots you may need neutral density filters to cut down
on the light transmitted to the film plane. One alternative to
light-cutting filtration would be to use a camera such as the
Mitchell which has a variable shutter. By adjusting the shutter
to 45 degrees at 1/15th of a second, the amount of light hitting
the film will be the same as if you were using a 180 degree shutter
at 1/60th of a second. In normal daylight situations this will
translate to an iris setting somewhere between f 8 and f 16.
Using the above rules let's say you want to
shoot a 6:00 PM sunset that will reach total darkness by 8:00
PM. First, begin to set up the camera around 3:00 PM so that
it is ready to roll by 4:00 PM to make sure you have at least
a couple of hours of head on the shot. Assuming the maximum shutter
speed of your camera is 1/15th of a second and you are using
ASA 50 film, set the iris at f 5.6 for the sunset. Even though
your meter reading at 4:00 PM will be about f 32, you will want
the film to slowly "fall into exposure" at sunset, and then "fall
out of exposure" as the sky turns dark, dropping at least five
f-stops so that you will have enough "tail" on the shot.
In certain cases once the image falls out of
exposure you may want to reset the camera to a slower shutter
speed and continue shooting. For example, if you are shooting
a sunset at f 5.6 and 1/15th of a second and after the sun has
set, your meter reading goes down to f 1.0, you may be able to "squeeze
out" another sunset shot by slowing the camera down to 4 seconds
per frame and letting the shot continue to capture any remaining
dusk-to-dark transition. The resulting shot will thus contain
two dusk-to-dark transitions of light and color in the sky. An
interesting effect may be achieved in editing by dissolving the
first sunset shot into the second one. This will give you a day-to-night
transition that will appear as if it were shot with continuous
exposure compensation; as though you used an auto-iris or shutter
control during filming (see the following section on "Norris" Light
Priority Control").
EXPOSURE INTERVALS AND THE MAGNIFICATION
OF TRAVEL
How often you expose a frame will determine
the speed at which the event will take place when projected at
24 fps. If, for example, you shoot one frame every two minutes
from 4:00 PM to 8:00 PM you will have a total of 120 frames (30
frames per hour) or five seconds of screen time.
Another important element to consider is the
effective "magnification of travel" of objects across the screen,
which depends on the focal length of the taking lens. Let's say
you are shooting clouds moving from left to right across the
frame. If you choose a long focal length lens such as a 100mm,
the clouds will cross the frame quickly, magnifying their time
of travel. On the other hand, clouds will cross the frame much
slower on a 14mm lens which will "reduce" their time of travel.
Consequently when a shot calls for a wide lens you may want to
lengthen the time between shots to speed up the clouds. Or conversely,
when you have a long lens on the camera you may want to shorten
the interval between shots to slow the action down. In this manner
you can control whether the clouds upon projection will look
like fast moving smoke or slow moving masses of water vapor.
Another example of magnification of travel
occurs when shooting moving traffic on a busy freeway or city
street. Here, several variables must be considered: (a) the speed
of the traffic, (b) the distance a car travels through the frame
during exposure, (c) the total number of cars in the frame, and
(d) the amount of light falling on fixed objects such as buildings
and roadways. Before shooting you first need to decide whether
you want to have long trails of lights moving through the frame
(two or more seconds per frame) or whether you want to freeze
the movement of the cars (1/30th of a second). Keep in mind also
that a tighter long lens shot typically will have more "trailing" or "streaking" due
to the magnification of travel. Further, if there is not much
traffic you will need to increase the exposure time to get longer
trails of car lights in each frame. There is a limit however
to how much exposure time you can give each frame before the
exposure on the stationary buildings, lights, roadway and the
like will become so bright as to cause the car lights to lose
their "punch."
The most exciting traffic shots are ones where
lights are continually moving. By using a 15 second or longer
exposure time you can capture an image on each frame that will
include such added elements as office lights being turned on
or off that might otherwise be missed with a shorter exposure.
As a rule most time lapse photography will benefit from long
exposure intervals because the final projected image will show
the greatest amount of activity.
As for the iris setting, the "climax"of a dusk-to-night
metropolitan cityscape shot will occur at the moment the buildings
in the frame become brighter than the sky behind them. This will
be the best time to take your exposure reading when scouting
the location.
NORRIS "LIGHT PRIORITY CONTROL"
An important time lapse device is the Norris "Light
Priority Control" (LPC) which samples light levels and adjusts
the motor or shutter speed of the camera in 1/1000th of a second
increments. The LPC continuously adjusts the light hitting the
film plane even during the exposure of a single frame. This device
will vary the motor or shutter with respect to the illumination
of a "reference target" which is set for the modified spot meter.
The spot meter monitors the light on the target, then communicates
with the intervalometer driving the motor. By using the LPC as
an "auto iris," you can film a day-to-night transition while
maintaining a constant overall exposure. Thus, you can have a
shot of city skyline with perfect exposure from 4:00 PM to 8:00
PM. As an illustration, say you begin with an f 16 at 1/15th
of a second at 4:00 PM. As the sky darkens the motor speed will
drop to approximately 60 seconds per frame by 8:00 PM. Even though
there may have been a ten stop change in light, the iris setting
stays the same throughout the shot, maintaining a constant depth
of field.
The LPC, which Norris describes as an intervalometer
with an automatic shutter speed control, has a menu button for
setting exposure (how long), interval (how often), and burst
(how many frames). Exposure is calculated through a light meter.
As the meter reading changes, the shutter speed is adjusted to
maintain a constant exposure. Shutter speeds vary from 1/16th
of a second to 990 seconds. Intervals vary from 1/4th of a second
to 100 hours, and bursts vary from 1 to 9,999 frames per pulse.
The LPC also has a convenient memory function which will save
the last calibrated set up. With the LPC, it is easier for the
time lapse cinematographer to spend time concentrating on the
compositional and thematic elements of a shot, knowing that transitions
will be smooth and exposure even.
SHOOTING A "POWER SHOT" FOR
OLIVER STONE'S "NIXON"
One of the unique challenges for a time lapse
cinematographer is to apply the demanding photographic techniques
to the creative process. On Nixon, I was presented with such
a challenge by the creative team of director Oliver Stone, director
of photography Robert Richardson asc, producer Clayton Townsend,
editor Hank Corwin, and post production supervisor Bill Brown.
Originally, the Nixon team sent me to Washington
DC to shoot a series of shots showing the passage of time around
various national monuments. The shots I made showed sunrises,
sunsets, rising moons, and moving clouds as backdrops to the
Washington and Lincoln Memorials and the dome of the United States
Capitol. The resulting shots were eye-catching, perhaps even
a little mystical, and did a good job of reflecting time passing.
After viewing my footage, however, Oliver Stone and the rest
of the team decided that they needed a more dramatic shot that
would portray the awesome power of the federal government. They
wanted a shot which would be "menacing", even "cryptic." Finally,
they decided on a shot of the Capitol that would show it as a "power
center" that was the "nucleus of energy" of the nation. So, in
August 1995, I was sent to DC for a second time to get the "power
shot."
Shortly before my trip, inventor Dan Norris
had sent a prototype of the LPC to me for experimentation. Because
of the LPC's unique ability to maintain a constant overall expo-sure
on a specific object while compensating for light changes around
it, I felt it would be the perfect item to help me achieve Stone's
vision by visually centering the shot on an unchanging and stable
Capitol, a rock amid a tumultuous sea of change.
Once in the nation's capital, I chose a camera
position atop a pillar about twelve feet above the ground. From
that vantage, the Capitol loomed over Pennsylvania Avenue. At
dusk, the "stars and stripes" created by the moving cars would
emerge and fill the lower half of the screen with the tremendous
energy of skittering lights. My goal was to provide a shot where
the Capitol would be engulfed in energy, like the nucleus of
an atom surrounded by randomly careening electrons.
The day-to-night transition I needed to photograph
was to take place between 6:30 and 8:00 pm, so around 4:00 pm,
as sunlight was striking the dome directly and as the light was
starting to turn yellow and drop in color temperature, I aimed
the LPC at the Capitol and started to roll film. Initially, the
shutter speed was 1/15 of a second per frame at 15 second intervals.
By nighttime, around 10:00 pm, the exposure was 60 seconds per
frame at 60.25 second intervals. Thus during the shot the illumination
on the Capitol essentially dropped by ten f-stops. As the shutter
speed decreased each moving car cast longer and longer light
streaks across the film stock. In addition an increasing number
of car lights passed through each frame. When the length of exposure
began to exceed the time between frames, the LPC automatically
expanded the time interval. Time magnified to the point where
everything began to move faster. More cars streaked through the
frame. Traffic signals cycled from green to yellow to red with
increasing rapidity until they became blurred flashes of color.
This gave the shot a greater feeling of excitement and created
the effect of a panic or an emergency. The resulting shot was
just what the director ordered. The Capitol is the focus of the
shot; there is an almost eerie absence of activity on the dome;
neither its illumination nor color appears to change as day turns
to night. In contrast, on Pennsylvania Avenue, traffic almost
explodes with activity. Thematically, the stability of our form
of government stands solidly above a ceaseless frenetic flow
of political intrigue and madness writhing beneath the surface.
That a government such as ours may withstand the Machiavellian
machinations of a politician and President such as Richard Milhous
Nixon is one of the strongest messages of the film. The shot
accurately echoed this sentiment.
On the following night, I attempted to recreate
this shot without using the LPC. The result was interesting,
even beautiful, but lacked the sense of combustion and pressure
of the LPC version and did not seem to have a point of "ignition" or "blast
off." To achieve Oliver Stone's vision, a contrast of sanity
and madness, I needed the unique capabilities of the LPC. At
the intersection of art and time lapse, there is a need to direct
an audience's attention to a certain image. Here, it was the
Capitol. In other motion pictures, it may be a character's home
or a dying rose given by a lover. On such occasions, the LPC
will be an important arrow in the time lapse cinematographer's
quiver of techniques. With such a tool the artistic possibilities
for telling a story through time passage are endless.
TEN STEPS TO TIME LAPSE
- Get permission to put the camera where you need it to avoid
the disappointment and embarrassment of getting shut down in
the middle of an all-day or all-night shot.
- Make sure your film is the right speed for your application.
For example, when shooting a star-filled nighttime sky use
high speed film, and when shooting a cloud-filled daytime sky
use low speed film.
- Set up your time lapse camera on location several hours before
the planned event or transition is to occur. Start the shot
early so you will have enough 'head' or lead-in time of exposed
frames on the shot.
- Rope or cone off the area around the camera, paying special
attention to the area in front of the lens so that passersby
will not ruin the shot inadvertently.
- Mount the camera securely and check that it is evenly balanced
on the support. Once the camera is rolling, make sure no one
touches it.
- Determine the desired screen time of the shot. Base your
interval calculations on the desired length, but lean toward
a slightly longer shot because nature is unpredictable. In
post production it is easy to speed up a shot but nearly impossible
to slow one down.
- If you expect light conditions to change, set your exposure
for the 'climax' of the shot, such as a sunrise or a sunset.
- Similarly, filtration and color temperature should be set
for the climax of the shot.
- Generally, daytime shots call for clouds. Be sure you have
proper rain protection for the camera and for yourself.
- Have plenty of food and water with you.
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