High speed sync and FP High speed sync

[gmahler5th]

What is the difference between high speed sync, which syncs at

1/250th on an F100 and FP High-Speed Sync for faster flash sync

speeds up to 1/4000 sec?

[ray]

There is nothing "high-speed" about syncing at 1/250. That is the mechanical sync speed.

Above that speed, both shutter curtains move in parallel causing the flash to strobe (turn

on and off multiple times).

 

Please note, that on the nikon film slrs, FP high speed sync is in manual flash only. No ttl.

On the newer digital slrs such as the D2h, FP high speed sync is in TTL.

[richard_cochran]

Right, 1/250 is just called X-sync, not High Speed Sync or FP sync. High Speed Sync is a synonym for FP Sync.

<p>

Anyway at X-sync of 1/250, the flash all happens in one very short

burst, so the flash can freeze motion, and all of the film gets

to receive light from the flash during the entire flash burst.

With FP sync, the flash is pulsed to create a very long stream

of light that illuminates the subject for the entire time the

shutter curtains are in motion. At those shutter speeds, the

shutter is never completely open, so most of the light

from the flash falls on the shutter curtains instead of on

the film, making FP sync less efficient. Since it's the

shutter, not the flash, that is in charge of freezing

motion with FP sync, it does a much poorer job of freezing

motion and isn't as suitable as X-sync for high speed

subjects.

<p>

See <a href="http://webs.lanset.com/rcochran/flash/hss.html">http://webs.lanset.com/rcochran/flash/hss.html</a> for details and sample photos showing how each method handles

motion.

[rhaytana__tim_adams_]

You might be interested in an article on Ken Rockwell's site related to this: http://www.kenrockwell.com/tech/syncspeed.htm

 

This non-expert photog uses FP Sync when I've got a roll of high speed film in my F100 in bright sun, I don't have the option of changing rolls and I want to get some kind of fill flash into the shot. My results are less predictable than with TTL flash, but often better than no flash at all.