Head is swimming..do I understand?

Olympus introduced high shutter speed flash over 20 years ago, and it has always been true that prolonging the output of light from the flash decreases its intensity.

Think of flash capacitor as a bucket of water. If you dump all the water instantaneously, the water has a lot of force. If you prolong the output of water simply by letting the water out a spigot rather then upending the bucket, the water lasts longer but has much less force.

jrsforums wrote:
OK....I had someone work out the logic and math for me...and it seems correct.

Without going all through it, keeping at max. sync flash by increasing aperture will yield ~2 stops stronger flash vs. using high speed flash. This is based on equivalent metering for ambient.

Tim....why did I ever doubt you...???

John

BTW...the above assumes that you require the maximum output from the flash that you can possibly get. In most cases, you will require significantly less than full 1/1 power, which then makes high sppeed flash an attractive alternative.

Here is a post with the details:
http://www.prophotocom​munity.com …n/0/page/0/gone​w/1#UNREAD

John

EOS systems (all the way back to 1992 at least), meter the ambient reading, then automatically add fill, day or night. It really is that simple. Try it. Please: try it.

All the theorizing is just each individual parsing their own understanding of the EOS system. Cameras capable of true spot metering may (may) do slightly better in the OP's individual situation, but not by much.
Evaluative metering (All) does the same job and most times better, most times flawlessly.

Tust the "Force" (EOS flash system)