Sequence viewing > Light & Lighting - Resource - ©
Lloyd Godman
Light in Photography - LIGHTING - FLASH
LIGHTING
FLASH
METERS & EXPOSURE.
Exposure
when using a flash depends upon two variables besides other considerations
like A.S.A. The distance the subject is from
the flash unit effects the amount of light reaching the subject,
while the tone of the subject itself may be a factor.
It
is possible to calculate the correct exposure for the flash
through calculation and this is done by using the "Guide numbers"
suggested by the manufacturer in relationship to the A.S.A.
and the distance the subject is from the unit. The "guide
number" relates to the power of the flash and is on the back
of some units.
This
is done by dividing the flash-to-subject distance, either
in feet or meters into the appropriate guide number to find
the correct
f stop. From the adjacent diagram if we divide 48ft into a
guide number of 96 the answer is f2. |
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IT
IS IMPORTANT THAT THE READING WITH THIS METER BE DONE WITH THE METER
POSITIONED WHERE THE SUBJECT IS, GENERALLY POINTING TOWARDS THE CAMERA
AS AN INCIDENT READING WOULD BE TAKEN.
Want to learn more? - do a workshop or one on one with Lloyd Godman
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