Dynalite Power Pack - Manual (Page 9)

Getting Started with Basic Lighting
Light Meters
It is recommended that you purchase a flash meter. This device measures the amount of light coming from
your flash system. This light can vary depending on the distance of the light from the subject and various light
modifiers, which are used to change the quality of the light. Flash meters are available from manufactures
such as Sekonic, which features PocketWizard technology in select models. Most flash meters are incident
flash meters, meaning you take the meter and point it back towards the camera from the perspective of the
subject to maintain an accurate reading of light falling upon the subject. You may also wish to point your me-
ter at the direction of the light source from the position of the subject when you are using multiple lights to
understand the ratios between the lights. Some meters are reflective meters (often referred to as spot meters)
and measure the light being reflected back from the subject taken from the camera position.
Halving and Doubling
Photography is based on the principle of halving and doubling. Shutter speeds are expressed this was as well
as the amount of light between f-stops. Your flash unit works based on the same principle. That is why the
units are expressed in terms of this numerology. Consequently, 250 watt/seconds will deliver twice as much
light as 125 watt/seconds and the relationship between these settings is one stop. Another thing to consider
is the inverse square law. As you double the distance between the light and the subject, you loose two f-stops
of illumination. (See inverse square law diagram.) Keep in mind the actual f-stop values vary depending on
the actual power of the light source.