Olympus E-3 User Manual page 54

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with the period needed to move the narrow slit between the first

and second curtain of a focal plane shutter entirely across the

frame, then we could ensure even exposure for all sections of the

Aha!

sensor.

If we consider the output graph of an FP enabled flash unit then

it would look like this:

1.2

0.8

0.6

0.4

0.2

In order to maintain the peak level of illumination, the stored

charge in the capacitor is released in a series of pulses. This

means that each "burst" of light is a fraction of the power of the

"full dump" – thus providing a lower level of light overall. This is

why FP mode flash exposure distances are considerably shorter

than those of normal emissions.

This is not really a problem, however, as most of the time one

would be using FP mode for fill-flash operations in bright sunlight

when shooting close-up portraits. The range of an FP unit's

emission is comfortably within the normal portrait photography

camera-to-subject distance ranges. In addition, the Olympus FL-

36/50 flash units constantly provide an available range read out

on their display panels so all that is needed is a glance at the

information display to check that you are within range.

GUIDE NUMBER vs. DISTANCE (MANUAL EXPOSURE)

The distance at which one may normally (i.e. non FP mode)

shoot with flash is governed by the equation

This is exactly what an FP capable flash unit does.

FP Flash Emission

Time (ms)

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