You're missing the fact that the amount of flash exposure you can work
into a shot is dependent only on the f stop. So if I shoot a backlit
portrait outdoors at f5.6, 1.250th, I can fill flash in at that 5.6
value. If I'm forced to stop down to f6.7 because I can't go beyond
1/180th in shutter speed, I lose flash exposure and increase DOF.
Ideally, I'd like to have flash synch up to 1/1000th, but that's
complex and cost;y. And high-speed synch doesn't help much, because
the flash power is greatly diminished by multiple firings.
Paul
On May 21, 2009, at 10:51 PM, Matthew Miller wrote:
On Thu, May 21, 2009 at 07:10:28PM -0600, William Robb wrote:
The difference between 1/180th and 1/250th flash synch is
substantial
when shooting a brightly backlit subject in bright daylight.
A lot can happen in 0.0016 seconds.
C'est what?
For example, someone walking by at a brisk pace of 4mph will move an
additional tenth of an inch. With a 1/250th sync, you could have
caught them
moving only 0.3 inches, but noooo, with Pentax's horrible 1/180th,
we're
stuck with a whole 0.4 inches of movement.
Of course, with hummingbirds, it's even worse. Why, at 1/180th, the
hummingbird's wings have gone through a whole 38% of a stroke. With
1/250th,
that'd be reduced to a mere 28%.
Okay, seriously -- the time difference just doesn't seem that much.
(1/643
of a second *different*.) Neither does half a stop. I accept that
there's
some narrow cases where it'd help, but I can't see it as the huge
deal that
it seems to be to some folks. What am I missing?
--
Matthew Miller [email protected] <http://mattdm.org/
>
The Definitive Pentax P-TTL Flash Model Guide: <http://pttl.mattdm.org/
>
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