Instruction manual

19
2.1 ISO, Shutter Speed, and Aperture
Airborne Photographers have to know the camera settings and how to set or
change them, so they can ensure the camera is properly set up for the mission
and quickly adjust to on-scene conditions. When you are flying is not the time to
learn how to change a camera setting.
The Videography Information Technology (VIT) Specialist needs to know how
to set or change camera settings in order to better understand what the camera
can and cannot do, and help train Airborne Photographer trainees on camera use.
Digital cameras work by opening their shutter for a brief time to allow light to
enter and interact with a light-sensitive photo-receptor; usually either a Charge
Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS)
sensor. Each pixel notes the variation in light rays that travel through the lens and
passes this information on to the camera’s microprocessor in the form of varying
electrical charges. The electrical charges are converted into digital bits and
stored on the memory card.
In addition to the camera shutter a camera lens can change the diameter of
its aperture, thus letting in more or less light. Thus sensor sensitivity setting
(ISO), the camera’s shutter speed and the size of the lens aperture all affect light
sensitivity and thus image exposure.
2.1.1 ISO
ISO defines how sensitive a camera’s sensor is to light. In digital cameras,
instead of changing film you can simply adjust the camera’s light sensitivity (ISO
rating). The higher the sensitivity, the less light is needed to make an exposure.
[Note: The International Organization for Standardization (ISO) has a
performance-based ISO speed standard for digital cameras, just as they have for
film. It defines ISO speed in terms of the amount of light needed to achieve a
certain quality.]
Lower ISO settings (where the sensor is less sensitive to light) are best used
in bright lighting conditions; higher ISO settings (the sensor is more sensitive to
light) can help in low-light situations such as early evening, winter or overcast
conditions. [However, higher sensitivity also amplifies undesired noise, which can
cause fringing or artifacts to appear in the photo. Most higher-end cameras don’t
show a noticeable increase in noise below ISO 800.]
Remember that changing the ISO setting affects aperture and shutter speed.
Some examples of when to use various ISO settings are:
Auto: The camera automatically sets the ISO speed according the brightness
of the scene, increasing or decreasing the sensitivity. You have no control over
which ISO number is used, but most digital cameras are set to ISO 100 (with
some as low as ISO 50). ISO 100 is the usual setting for most CAP videography.
50-80: For taking photos in bright light; excellent for close-ups, landscape,
and portraits, these settings produce fine detail and image quality