Doug Kerr
Well-known member
For what it's worth, with a Canon EOS 40D and Canon Speedlite 580EX II, with the system in the FP mode (called "high-speed sync"), the sync timing at the flash sync PC connector on the 40D is apparently X-sync (trigger closure when the first curtain is completely open).
This was determined by making the 580EX II not contribute substantially to exposure (set to Manual, 1/128 output, and the head pointed away from the test scene) and firing a Vivitar 285HV from the PC connector on the 40D. The partial exposure of the frame, for fast shutter speeds, is the same with the system in FP mode or not.
Note that in the Canon system, with "older" EOS cameras, the system must be put in FP mode by a setting on the dedicated flash unit (e.g., 580EX II) itself, but the camera is of course aware of it. In more modern cameras, including the 40D, the FP setting can be made from the camera, but the intimation is that in that case we make a setting on the flash from the camera, which then advises the camera.
No surprise here, but just another data point on the misthaufen.
The Canon dedicated flash units do not provide a sync output to electrically fire another external flash, so I cannot test the Deal deal.
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As a matter of gratuitous historical interest, note that the "X" in "X-sync" means "zero shutter opening delay after sync closure". It goes back to the days when, to accommodate the lag in the peaking of flash lamp output, the shutter opening was delayed from sync closure (with fancier shutters, by one of two time delays for different classes of flash lamp - but often just the "M" - medium - delay, suitable for the most common "consumer" class).
When electronic flash was introduced, no such delay was needed, and a setting of "X" on the delay selector meant "delay: disable".
In fact, it was then important that the sync closure was itself delayed until the shutter was fully open, often a new wrinkle in the shutter mechanism design.
Then, the shutters often had a selector lever for "X" vs. "M" delay.
Often that delay timer was hijacked for the "self-timer function", which then was a third setting of the lever - "V" (for vorlauf, German for "pre-run"). In that case the sync timing was "X" whether that's what you wanted or not.
Best regards,
Doug
This was determined by making the 580EX II not contribute substantially to exposure (set to Manual, 1/128 output, and the head pointed away from the test scene) and firing a Vivitar 285HV from the PC connector on the 40D. The partial exposure of the frame, for fast shutter speeds, is the same with the system in FP mode or not.
In older EOS cameras, this output came directly from an electromechanical contact on the shutter, so it is not surprising that it has a consistent timing with respect to shutter operation.
Note that in the Canon system, with "older" EOS cameras, the system must be put in FP mode by a setting on the dedicated flash unit (e.g., 580EX II) itself, but the camera is of course aware of it. In more modern cameras, including the 40D, the FP setting can be made from the camera, but the intimation is that in that case we make a setting on the flash from the camera, which then advises the camera.
No surprise here, but just another data point on the misthaufen.
The Canon dedicated flash units do not provide a sync output to electrically fire another external flash, so I cannot test the Deal deal.
********
As a matter of gratuitous historical interest, note that the "X" in "X-sync" means "zero shutter opening delay after sync closure". It goes back to the days when, to accommodate the lag in the peaking of flash lamp output, the shutter opening was delayed from sync closure (with fancier shutters, by one of two time delays for different classes of flash lamp - but often just the "M" - medium - delay, suitable for the most common "consumer" class).
When electronic flash was introduced, no such delay was needed, and a setting of "X" on the delay selector meant "delay: disable".
In fact, it was then important that the sync closure was itself delayed until the shutter was fully open, often a new wrinkle in the shutter mechanism design.
Then, the shutters often had a selector lever for "X" vs. "M" delay.
Often that delay timer was hijacked for the "self-timer function", which then was a third setting of the lever - "V" (for vorlauf, German for "pre-run"). In that case the sync timing was "X" whether that's what you wanted or not.
Best regards,
Doug