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[OM] Re: Remote flash: was It is now official ...

Subject: [OM] Re: Remote flash: was It is now official ...
From: "Ken Norton" <ken@xxxxxxxxxxx>
Date: Fri, 31 Oct 2008 09:49:51 -0500
Chuck, I believe the latency numbers are calculated theoretical minimums.
Kinda like how Behringer calculates the specs for their audio products.  ;/

Just thinking off the top of my head:

1. Transmit rate is most likely no higher than 9600 baud.
2. Datagram could be like four bytes or 32 bits.
3. The entire datagram would take 1/300 of a second to transmit
4. To achieve 1/4000 of a second, they could only be transmitting two
bits--not including ANY processing time.
5. It is impossible to provide adequate channel assignment and protection
from falsing with only two bits.
6. If one were to do this with ONE byte datagrams, at 9600 bps, it would
take 1/1200 of a second for transmittion of the datagram.
7. These triggers are required to operate in the ISM (Industrial,
Scientific, Medical) bands. As such, there is plenty of other data
interference in the air on those same frequencies, so you'd need a larger
datagram to coexist with other wireless devices.

To do this right with adequate falsing prevention, device control and
assignment, I can't imagine trying to do this with fewer than 8-bits.
Figuring a 50% overhead in detection and processing, it would take 1/800 of
a second before the trigger would fire.  The next question is whether the
trigger itself is transister-based or relay based?  Either way, you will
have a ramp-time delay.

Now, consider that a strobe fires in a non-linear manner with the bulk of
the light emitted approximately 2/3 into the pulse.  Consider the other
delays within the flash's electronics itself.  I've found that using my
Minolta A1 as a test device when I fire strobes directly attached to the
camera that I get varying response rates with some flashes fully
illuminating the scene at 1/640 and others as low as 1/250.  Monolites seem
to be worse than the Vivitars.  At 1/250 everything works with the A1, but
if I'm using the ebay remotes, I need to back that off to 1/200 or less.

Maybe Wayne can shed a little light in here on this subject, but I suspect
that any claims of 1/4000 response are a "bit" optimistic.

AG


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