How do the SB-800 and SB-600 talk?

Hi:

Anyone know how the Nikon SB-800, SB-600, D70s, D200, etc. "talk" to
each other? It's not via RF and I was told it's not via IR. Someone
told me that it's not IR but that the speedlights are "optically"
driven. Technically, IR is optical since it's light. So, I don't know
what "optically" driven means. Anybody know the mechanism? I couldn't
find it in the manual.

Thanks.
Kevin

My understanding is (ok, that should be enough disclosure) that they
work by light output as read by the iTTL sensor in the camera. Once
enough light (from all flashes - I have 2 600's slaving off one 800 on
camera) reaches the "film plane" or sensor, the rest of the flash is
stopped (time wise).

k-man schrieb:
Hi:

Anyone know how the Nikon SB-800, SB-600, D70s, D200, etc. "talk" to
each other? It's not via RF and I was told it's not via IR. Someone
told me that it's not IR but that the speedlights are "optically"
driven.

The master sends commands to the slaves vie modulated preflashes. There
is no communication channel in the opposite direction except that the
master measures the strength of the preflashes of the slaves.

Walter

You can download an info pdf from Nikon.

The Sb800 and "Master" capable cameras (D70, D2X, D200 etc). send out a
pulsed series of preflashes to monitor ambient light and subject reflection,
then the "master" designated unit will send a second coded flash sequence
which is read by the "slave" units, (other SB800 & Sb600s. The SB600 is
weaker and not able to function as a "master" unit, only as a slave) and
adjusts the power settings and a third pulse to trigger all the units.
In use what you see is a brief visible flickering of the flash units when
you fire the shutter and then the main pop of all the units going off
together. the delay between shutter release/preflash/communication
flash/final exposure flash is significant, around 1/4 - 1/2 second.

The system works brilliantly and is very accurate and quick to use where
variable conditions are involved outdoors. Fantastic for outdoor closeups of
insects/flowers etc, where one flash can be on camera and another can be
handheld for back/rimlighting by yourself or an assistant, or have it on a
lightstand.

With more than 2-3 flashes its quicker to just put them on manual, set the
power yourself (quick and easy with digital preview) and trigger using the
slave function of the nikon units which will then work nicely with bigger
metz's and studio flashes.

Bright sunlight shortens the range of this communication substantially.
The perflash and communication flashes are irritating to many people, many
many people blink on the preflashes and the actual shot ends up with closed
eyes. At least you can chimp and check on the LCD!
You can't use the master/slave systems in conjunction with studio flashes as
the preflash triggers them.

Regards,
Frank Styevko from OZ

"k-man" wrote in message
ups.com...
Hi:

Anyone know how the Nikon SB-800, SB-600, D70s, D200, etc. "talk" to
each other? It's not via RF and I was told it's not via IR. Someone
told me that it's not IR but that the speedlights are "optically"
driven. Technically, IR is optical since it's light. So, I don't know
what "optically" driven means. Anybody know the mechanism? I couldn't
find it in the manual.

Thanks.
Kevin

Thank you all very much. I wasn't aware that the pre-flashes did
anything more than send potential exposure information back to the
camera. That's an impressive system. Info gathered at the speed of
light.

Another question: With something like the SB-800, you can turn off the
flash yet still have it act as a master. I guess in that case it still
sends pre-flashes but doesn't fire during the exposure. Right?

Thanks again.
Kevin

Correct.
As mentioned previously you can also do this with i-TTL enabled cameras
(D70, D2X, D200 etc) using the inbuilt pop-up flash unit.
You set the functions for this in the cameras menus for flash operation.

The built in flash is then only used as a signalling device. I'm not sure
which part of the camera does the "recieving" though, but thatsnot important
as long as it works.

--
Regards,
Frank Styevko from OZ

"k-man" wrote in message
oups.com...
Thank you all very much. I wasn't aware that the pre-flashes did
anything more than send potential exposure information back to the
camera. That's an impressive system. Info gathered at the speed of
light.

Another question: With something like the SB-800, you can turn off the
flash yet still have it act as a master. I guess in that case it still
sends pre-flashes but doesn't fire during the exposure. Right?

Thanks again.
Kevin