SB400 vs. SB600?

[Stoller]

... But does it fire pre-flash? D200 manual (p163-167).

SB800 does. I don't have manual at my work so I can't look at what you are refering to.

[murrays]

I am pretty sure the on-board controller communicates via pre-flash signals to the remote unit(s). I guess I am going to have to confirm this by looking it up... but I think the SU-800 and SB-800 controllers might communicate via another method?

Ok, without confirming the SU-800 and SB-800 the D80 manual does explain (p 96 - 97) that the pop-up flash will need to be up so that the "timing" sequence can be sent to the remote flash units. It also makes suggestions as mentioned previously to keep iso low, and exposure settings at levels that will not be affected by the pre-flash series.

This is correct, the camera communicates to the remote flash(s) with "pre-flash signals"; there are no infra red signals. Here's a long exposure that show's the sequence:



Explanation here: http://www.imaging-resource.com/PRODS/D70/D70P.HTM

Here's what I think is happening in the shot above:

D70 fires a "wake up" series of command pulses, to get the attention of any remotes that might be out there, lying dormant. (Note that what looks like a single bright flash here is actually a very rapid series of communication pulses, carrying digital data from the D70 to the remotes.)

D70 fires a command pulse stream to instruct the remote(s) to get ready to fire a metering pulse.

D70 fires a single, (low power) trigger pulse. The SB-800 fires in synchrony with it. This is the metering pulse.

(Then there's a pause, while the D-70 digests the results of the metering pulse, and computes the correct exposure based on its TTL measurement.)

The D70 fires a series of command pulses, instructing the remotes to get ready for the main exposure flash, and telling them what power level to fire at.

The D70 fires a single trigger pulse. The SB-800 fires in synchrony with it. This is the main exposure flash.

-murray

[Stoller]

This is correct, the camera communicates to the remote flash(s) with "pre-flash signals"; there are no infra red signals. Here's a long exposure that show's the sequence:

I'm going to have research this, I think the Pre-flashes are for metering...

[murrays]

I'm going to have research this, I think the Pre-flashes are for metering...

IIRC, infra red requires line of site between the camera and the flash. If that's the case, you can put the flash behind some obstruction (a chair, for example) and it will still work.

-murray

[murrays]

Also, from http://www.kenrockwell.com/nikon/ittlslave.htm

You have to pop up the camera's built-in flash. The light from the camera's flash becomes the controller and trigger for the other flashes. On a D50, or camera lacking built-in flash, you have to use an SB-800 or SU-800 on the camera as the controller.

-murray

[Stoller]

From dpreview.com

Additionally, for those desiring full creative control of the output of each individual Slave, the photographer can remotely control each of Slave SB-800 Speedlight unit’s flash modes directly through the Master unit.

The Master unit output can even be switched off whilst maintaining full control and communication with Slave units.

http://www.dpreview.com/news/0307/03...nikonsb800.asp

I will do some testing when I get home this evening.

[Stoller]

Ok wireless remote flash is triggered by the on board flash. I think I was getting SB800 operation confused with when I have used the SC-29 TTL remote cable and the SB800. With the cable you don't need the on board flash open and you also don't have the pre-flashes.

It all boils down to me not using my own equipment enough. Gives us something to chat about, my stupidity

[Rooz]

ok that sorts that out...sooooo, if the "light" so to speak triggers the remote flash why cant the sb400 mounted not do the same ?

can someone please buy an sb400 and sb600 to sort this out.

[murrays]

ok that sorts that out...sooooo, if the "light" so to speak triggers the remote flash why cant the sb400 mounted not do the same ?

can someone please buy an sb400 and sb600 to sort this out.

Actually, I don't think an SB600 can't be used as a trigger either, at least not on a D70s.

-murray

[achuang]

ok that sorts that out...sooooo, if the "light" so to speak triggers the remote flash why cant the sb400 mounted not do the same ?

can someone please buy an sb400 and sb600 to sort this out.

The light does trigger the remote flash, but it has to be in a specific sequence to communicate with the remote flash. This sequence of flashes is only available in the commander mode. Do you notice when you take a shot using remote flash that it takes a bit longer for the shutter to fire because of all the preflashes of the popup flash communicating with the remote? The SB400 doesn't have this commander mode built in like the SB800 so it can't control remote flashes. I feel the same Rooz, I wish that it could so I could have a bit of flash onboard the camera to give a bit of fill light. At least your D80 contributes flash to the exposure. Hope this helps. The picture and site that murrays posted is the one I'd read in the past and explained it quite well.