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Old Mar 2, 2007, 4:15 AM   #1
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Hi All

I will start with the questions (my camera: Canon EOS 350D)

What determines the max flash sync speed
Camera?
Flash?
Both?

I know at the mo using onboard flash my max flash sync speed is 1/200.

If i buy the 430ex will my max flash sync speed be the same?????



Ideally i want to be able to shoot in very bright light and use the external flash as fill while stll using wide aps. so shutter speeds of like 1/1k+

Any help or clarification would be appreciated

cheers
Ken
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Old Mar 2, 2007, 7:35 AM   #2
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The 430EX has an available FP mode (a.k.a., High Speed Sync).

This allows you to use shutter speeds faster than the camera's x-sync speed.

This gets around the problem you have trying to use a flash that only gives out one flash burst (since the entire film or ccd won't be completely exposed by a single burst once you get faster than the x-sync speed.

At speeds faster than the maximum x-sync speed, the shutter curtains can't move fast enough to fully open and close during the time allocated for exposure. So, at faster shutter speeds, the second curtain begins to close before the first curtain fully opens. That results in a travelling slit of light (which means the entire film or ccd would not be exposed with a single flash burst at faster shutter speeds because the flash burst is too short).

A flash with an FP (High Speed Sync) mode gets around this limitation by pulsing the light during the entire time the shutter curtains are travelling.

Just keep in mind that you'll have a significant loss of power with a flash used that way (because it's trying to pulse the light versus using just one flash burst). IOW, as soon as you exceed the camera's x-sync speed (1/200 second with your XT) using a flash like the 430EX, you'll probably lose at least half of it's rated flash power for distance purposes at any given aperture/iso speed setting.


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Old Mar 2, 2007, 2:51 PM   #3
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thanks Jim

im all clear now

ken
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