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Updated: 12/06/2007
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Determining the EI / ISO / ASA*Sensitivity of a Video Camera Although
video camera manufacturers talk about the lux or
foot-candle sensitivity of their cameras, few provide
any EI equivalents, which is what Directors of Photography
in film and motion pictures
have long relied on in evaluating the lighting
in scenes.
Light sensitivity is important when there is a need to consider depth of field and selective focus prospects in a particular setting. "Crossover" cameramen may also need to know if a particular video camera will be able to get pictures in the same light conditions that their 35mm camera did when it was loaded with 500 speed film. Here is a procedure for determining the EI sensitivity of a video camera. For this you will need a waveform monitor, a standard video chip chart, and a incident light meter. 1. Focus the camera on an evenly illuminated chip chart and observe the waveform. 2. Open the camera's iris until the white chip is at 100 (or the crossover chip equals 55 IRE units). 3. Take readings from the surface of the chip chart. Depending on your meter, either alternate slides on the meter until your reading equals the f-stop of the camera, or advance the EI settings until the meter agrees with the f-stop on the camera. The EI speed you end up with is the speed of your video camera. If
you want to find out what the speed indexes are at
different dB gain settings on the camera -- which
would be equivalent to push processing the film
to various degrees -- just repeat the process with
each gain boost setting.
When you get done, you can make a chart for yourself showing all of your video gain settings and the equivalent EI speeds.
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