Thread: You can with a Nikon, not with a Canon ;-))
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Old September 13th 07, 11:53 AM posted to aus.photo,fr.rec.photo,rec.photo.digital
Sosumi
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Posts: 461
Default You can with a Nikon, not with a Canon ;-))

I think itīs a great idea!
Thanks, Iīm going to try it!

"Wayne" wrote in message
...
In article ,
says...

Thatīs all. The camera thinks it has no flash and all automatic stuff is
gone, but the flash DOES fire!! So I was able to FREEZE falling water from
the tap in the kitchen. Very cool!!


The obvious question is why would you want to set the shutter speed to
1/4000
second for this? A totally unnecessary complication.

Flash exposure is only about aperture and flash power. NOT about shutter
speed. You only want the shutter to be open for flash. The only time you
would care about exact shutter speed is for ambient lighting, if somehow
mixed
in the same frame (like outdoors in daylight - then matching the two
exposures is necessary). At any one given aperture and ISO, then shutter
speed controls ambient exposure, and flash power controls flash exposure.
This is simply how things work.

With regard to freezing your falling water, try this:

Set lens aperture to maybe f/16 (for depth, am assuming up close)

Set shutter speed to Bulb, where it stays open as long as you hold the
button
down (a couple of seconds). Set ISO 200.

Set SB-800 flash to Manual, at lowest 1/128 power level (for fastest
speed),
at perhaps 8 inches (20 cm) from water subject (assuming flash zoom
setting
is at 24mm). Vary this ballpark distance in or out, as needed for proper
exposure.

Open shutter (hold button down in Bulb)

Start the water drop moving, or whatever.

Fire SB-800 flash in manual from maybe 8 inches (for water drops)
(assuming it is timed to be at the right instant desired as subject).

Then we are done, so close shutter by letting go of shutter button to shut
it.
Shutter was open maybe 1 or 2 seconds (shutter speed), but the water drop
is
perfectly frozen by the flash speed.. Which duration is 1/41,400 second
for
Nikon SB-800 at 1/128 power.

The 1/41,400 second flash is much faster than the 1/4000 second shutter,
and
the shutter has no effect at all (so long as it was open). Even when the
shutter speed was two seconds, it still has no effect at all (in this
case).

The 1/41,4000 second flash duration stops the motion. Not the shutter.
Indoors in a halfway dim room, the ambient will not register in a couple
of
seconds.

Theoretically, you might choose to use a tremendously slow flash unit with
a
fast enough shutter speed to matter, but why would you possibly want to?

See http://www.scantips.com/speed.html about why speed lights are called
speed
lights, and regarding stopping motion with flash.

--
Wayne
http://www.scantips.com "A few scanning tips"