Calculating exposure with flash

Started Dec 27, 2012 | Discussions thread
BAK Forum Pro • Posts: 22,372
About 1/1 and 1/2 and 1/4, etc

a/ set up your light and decide what aperture you want. Let's say for some reason you want to use f5.6

b/ Guess at some power level, based on experience, or just set it at full power.

c/ Take a meter reading. Let's say it tells you f16 is correct. Do some math in your head. f16 to f11 is one stop. f11 to f8 is another stop. And f8 to f5.6 is one more stop. That's three stops total.

d/ Adust the power level by turning to 1/2, taking care of one stop, and then to 1/4, killing a second stop, and then to 1/8, which kills the third stop. Each change cuts the expose in half, which is a stop.

Take another meter reading, and you'll be close to f5.6, which is what you want to use.

It's easy to move the light a bit closer or farther away to get right to f5.6 instead of near to it. And some flash units let you make very small changes in power, often as precise as 1/10 of a stop.


Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow