The Time-Lapse FAQ

By E.M. Kinsman

Chapter 4:  Notes on Growing Plants:  

Plants have several requirements needed to make them grow and bloom - some of these are:

a. Temperature
b. Humidity
c. Light quality
d. Light duration

Of these variables, temperature seems to be the most important. Since I photograph in a studio that averages 65 degrees in the winter and 74 in the summer. These average temperatures can be increased with the use of a variac and a heating pad. The heating pad is a 35 watt heater used to keep iguanas warm.  These are available from pet suppliers and are a 13 x13 inches square. These flat heaters can be placed under a pot to supply bottom heat to the plants. There are also special heaters that are sold to keep seeds warm for germination. Either heater system works well.

Light Duration:

The light duration can be either computer controlled, or a simple house light timer can be used in series with the computer controlled relay. Plants will become stressed if lights are left on for 24 hours a day and some will not bloom, or will bloom very slowly. The duration of lights should be kept close to what the plants are used to, if plants are collected from the wild, try to keep the grow lights in phase with the current sunrise and set.

Light Quality / Spectrum The spectrum of the glow lights can be very important for some varieties of plants. Morning glories require a spectrum close to the solar spectrum to insure blooming, the duration of the light is also very important. The simple act of turning on photo lights every few minutes can mess up the photo cycle of the plant. Poinsettias are very particular about having an uninterrupted dark or "rest" period.

I typically grow plants outside, in a green house, or collect wild specimens. These plants are moved into the photo studio at the appropriate time to photograph the desired motion. Many plants will still grow and bloom if a part is cut off and moved into the photo studio. Things like flowers can be cut, placed in water then photographed. As long as the action takes less than a few days the photography can be completed before the plant wilts. Frequently requested shots like roses take special precautions. Roses require a thin wire to be wrapped around the stem to insure proper positioning. Roses will quickly follow a light source. Roses can also be brought into the studio in potted containers, sprayed with an insecticide (unless you are trying to photograph crawling creatures) wired up, and photographed. Of all the flowering plants, photo editors request roses 10 to 1 over everything else.  The reason is that not many people can film roses, typically you have to grow your own.  Of all the plants roses are second in difficulty to poppies.

Many plants require special techniques, these process often lead to new discoveries about the motion of plants. Most plants have never been time-lapse photographed, so new discoveries are abound.

Many if not most plants exhibit phototropism, that is they follow the sun. Leaves will rise to meet the light and then bend down at night. Plants like dandelions will do this on a continuous basis, while their flowers will follow the sun. This can lead to problems if the grow light is in a different direction than the camera's lens. What happens is the plant bends towards the grow light and away from the camera. A way to control this problem is the have a large light placed near the camera. This main grow light keeps the flower, or leaf pointing in the correct direction. Wire can be used to wrap the stem. This keeps the plant in from moving.

Timing: Timing for plants is best at one shot every three minutes, or a longer duration is the plant is particularly slow moving. Flowers that open with the sun such as morning lilies will open completely in three hours, plan your duration in response to the length of the final footage. It is often best to test timing and technique for the specimen before filming.

I believe that most time-lapse sequences should be around 12 seconds. (many of mine have been digitally edited to a few seconds) Many times the length of film will be much longer than the target 12 seconds due to waiting for an event to happen. An example would be taking a frame every 3 minutes for 4 days, waiting for a flower bud to open.

In regards to timing, it is always safe to error on the side of taking frames too fast. Sequences can always be speeded up in the digital editing world. This often happens.

The rule of -thumb is the higher the magnification the shorter the time between frames.

There are many discussions on grow lights that imitate the solar spectrum. White florescent lights work just as well as the grow lights for most plants. What is very important is light levels. The brighter the better. A bank of 6 tubes of florescent lights is very nice for growing the plants.

Photo Lights: The problem with time-lapse photography and lights is the lights have to turn on and off a large number of times. Fluorescent lights are designed to do this, but are the wrong color temperature and spectrum for photography. Halogen lights that are nicely color balanced are expensive, hot, stabilize quickly, but must be left on for a minimum of ten minutes to allow the halogen chemistry to properly cycle. Although a halogen light will burn full strength to 75 hours, it will only turn on and off 400 times. The means that a halogen bulb is a very expensive source of lights, and fairly unreliable. There is a large probability that the bulb will burn out during a shoot.

The solution is to use inexpensive incandescent tungsten photo bulbs. These bulbs are about $2.50 in bulk. These lamps are balanced for 3200 degrees K and will last for 2500 duty cycles. When they start to turn brown, I replace them with a fresh lamp. I keep the used bulbs for photography requiring constant use lamps. This is the best solution to the lamp problem I have found so far.

There is the possibility to use photoflash lamps, but a special trigger circuit would have to be built. These flash units are fairly expensive. A system that opened the shutter, triggered the flash, then closed the shutter would be a nice system that could achieve large depth of focus with a small #f.

Kino flo lights: These florescent lights are specifically designed for professional photography. They can take a tremendous number of duty cycles and although they are expensive to initially purchase they will pay for themselves over time.

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