Light is one of life's most necessary elements. It gives plants energy, our earth warmth,
and helps our eyes to see color and shape. For these reasons and more, light is very
important for cameras. If it is controlled right, the sensor can easily define shape
and capture a clean image which can help you make a video that can impress those around
you.
Controlling light in a camera starts with controlling exposure. Exposure refers to the
length of time that a camera's imaging device gets hit by light. Here's how it works. First,
light passes through the lens of the camera stopping at the diaphragm or iris. The iris,
which acts much like the iris in our eyes, opens slightly to let in less light or wider
to let in more light depending on the strength of the light coming into the camera. Once
it passes through the iris, it must pass through the shutter gate in some cameras. The shutter
gate covers a sensor for a determined length then opens to let light in. Lastly, light
reaches a sensor where the photons that make up light are captured, collected, converted
into electrons and read by a computer. The more electrons in each pixel, the brighter
that pixel will be during playback. The resulting ones and zeroes then get written to a recording
medium and read on a computer during editing or playback.
One of the most used methods of controlling light is by setting a camera's aperture. The
aperture controls two main functions: the amount of light that hits the camera and the
depth of field
The iris or diaphragm on a camera is a multi-bladed opening that controls how much light hits
the sensor. Much like your eye, the wider the iris, the brighter the image gets. Aperture
is measured in f - or focal stops. Each stop down represents half of the light that was
previously entering through the lens. The tricky part to remember is that the higher
the f-stop number, the smaller the opening. As such, f22 on a camcorder usually blocks
the most light while f1.8 usually means the iris is wide open.
Due to the way optics work, the wider the iris opening, the shallower the depth of field
is in an image. Depth of field refers to how much of an image your lens can focus on at
one time. If your lens can focus both near and far at the same time, you have a deep
depth of field. If only near or only far, it has a shallow depth of field. Since an
out of focus background can help you to draw focus on your subject, a shallow depth of
field is usually desired. Opening your iris to its widest setting, usually f/1.8, will
allow you to get the most shallow depth of field and draw focus to certain areas of your
image.
When controlling light, it is also helpful to know the functions of a camcorder's shutter.
The shutter is a window that sits in front of the sensor in a camcorder. This window
opens for a short period of time to cut down the amount of light that hits the sensor and
to lessen motion blur.
The simplest use for the shutter is to cut down on the amount of light that hits the
sensor. By keeping the shutter gate open for only a short period of time, a sensor can
gather very little light, making the image look darker. This can work well when in a
bright outdoor environment. However, in a darker indoor environment, shutter speed is
usually set to its minimum
The most common use for shutter speed is to either create more or less motion blur in
an image. Motion blur is when an object moves across the frame during the time a shutter
is open. This results in streaks where the the object was in the frame. Motion blur can
be eliminated by opening the shutter for very short periods of time - either 1/2000th of
a second or shorter - in order to cut down on the distance the object can travel in the
frame before the shutter closes again. A fast shutter speed is often used in sports videography
as it leads to better definition during slow motion replays.
The last method of controlling light in a camcorder is by using a built in neutral density
filter. Neutral density filters are pieces of shaded glass that are placed in front of
the lens in order to cut down the intensity of the light entering the camera. These filters
act like sunglasses for a camera. They are usually located at the front of a camera as
a switch that can select between three different filters. These filters are usually measured
by how much light they cut from the camera in f-stops.
The aperture, shutter speed, and neutral density filters in your camera are great tools for
helping you to control how light reaches your camera's sensor. Knowing how each one works
and how to use them in concert with each other can take some time. However, that knowledge
will result in beautiful images that can be captured under any lighting condition.