SB700 has built in optical slave! SU4 Mode

Started Sep 20, 2011 | Discussions
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blickblocks Regular Member • Posts: 101
SB700 has built in optical slave! SU4 Mode

Now, this isn't such a huge deal for people with camera bodies that can handle being a CLS Commander, but it is a handy feature nonetheless that I certainly didn't expect. In the menu, under "Remote" you can select SU4 mode, which allows the flash to optically slave when set as a remote flash. The TTL setting becomes an automatic mode and manual, well, manual. On your camera body turn off TTL and set the flash to a low power on manual, and this will allow the SB700 to fire when the shutter is open.

Anybody know the details of the auto mode when used as an SU4 slave? I'm intrigued. Since you don't input distance, ISO, or aperture how does it know? Optical sensor?

Alex Notpro
Alex Notpro Contributing Member • Posts: 982
Re: SB700 has built in optical slave! SU4 Mode

How does it deal with pre-flash? Do you have to disable pre-flash by going to manual flash?

I'm waiting for my own SB-700 to arrive, and will test this out when it does I have a D5100, which lacks CLS Commander mode.

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blickblocks OP Regular Member • Posts: 101
Re: SB700 has built in optical slave! SU4 Mode

Alex Notpro wrote:

How does it deal with pre-flash? Do you have to disable pre-flash by going to manual flash?

I'm waiting for my own SB-700 to arrive, and will test this out when it does I have a D5100, which lacks CLS Commander mode.

Yes, you must put the built in flash in manual, not iTTL, so there is a single flash.

I'm so happy with my SB700, the only disappointment is that it doesn't work with regular TTL, so it's not compatible with most film bodies (I think the F6 is the only one it works with, my backup body is an F100). I'm sure you will enjoy yours!

GraemeF Junior Member • Posts: 28
Re: SB700 has built in optical slave! SU4 Mode

blickblocks wrote:

I'm so happy with my SB700, the only disappointment is that it doesn't work with regular TTL, so it's not compatible with most film bodies (I think the F6 is the only one it works with, my backup body is an F100). I'm sure you will enjoy yours!

The SB-900 has the same issue - point blank refused to talk to my F5! If you want TTL compatibility with any of the older film bodies, you need the SB-600 or SB-800.

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instamatic Veteran Member • Posts: 3,563
Re: SB700 has built in optical slave! SU4 Mode

Hello,

SU-4 mode allows for wireless TTL flash photography on film cameras that rely on off-the film flash metering. Those are cameras like the F100, F5, N80, N75, and N65 I think. On the digital side, Fuji S2 can use this mode I think. F6 uses the current iTTL/CLS approach, but I think it should also be backwards compatible, one of the few bodies actually, with the D2x / D2h being perhaps the others I think.

When you set the SU-4 mode on a flash, in my case I have experience with the SB-800's and an F100, the flash will automatically detect whether it is mounted on a camera or not. If it is mounted it will automatically turn into "master" mode. If it is not mounted, it will automatically become a "remote" unit. Preflashes will be automatically cancelled AFAIK aside from post flashes to quench the remote speedlights. I don't know if there are any other preflashes emitted or not.

In a properly set up SU-4 configuration, you will get TTL control with all the flashes firing, but you won't be able to adjust flash exposure compensation on individual lights. In practice it still looks very well, and is a quite useful mode if you still occasionally use film and have a body that supports this flash mode. I think using flash modifiers may negatively affect as the flashes are not independent of each other in flash duration. I haven't tried, so I don't know.

The other benefit of the SU-4 mode is the manual mode, in which the flash becomes a dumb-fire remote unit and you can set it's power manually on the speedlight itself. It will become triggered by any other flash in it's proximity. Preflashes from other units will trigger that SU-4 configured flash prematurely.

blickblocks OP Regular Member • Posts: 101
Re: SB700 has built in optical slave! SU4 Mode

The SB700 won't work in TTL when it's placed on the camera. That's pretty odd that you could slave it in SU-4 to a TTL compatible master speedlight and still maintain TTL...I need to call Nikon and see what they have to say about this.

instamatic Veteran Member • Posts: 3,563
Re: SB700 has built in optical slave! SU4 Mode

Possibly they have done away with the SU-4 "Master" feature on the SB-700 just like they done away with TTL compatibility with the film cameras sans the F6.

My SB-800 clearly becomes an SU-4 TTL master when mounted on the F100, and the appropriate indicator on the flash's screen on the back says so.

So the SB-700 is probably not "fully" SU-4 compliant, just designed for the "remote" mode.

This further increases the value of the SB-800 in my eyes.

blickblocks OP Regular Member • Posts: 101
Re: SB700 has built in optical slave! SU4 Mode

instamatic wrote:

Possibly they have done away with the SU-4 "Master" feature on the SB-700 just like they done away with TTL compatibility with the film cameras sans the F6.

My SB-800 clearly becomes an SU-4 TTL master when mounted on the F100, and the appropriate indicator on the flash's screen on the back says so.

So the SB-700 is probably not "fully" SU-4 compliant, just designed for the "remote" mode.

This further increases the value of the SB-800 in my eyes.

Hmm. I had decided against the 800 given it's propensity for melting but if I could do SU-4 with 800 as master and CLS with 700 as master it might be worth having both around.

blickblocks OP Regular Member • Posts: 101
Re: SB700 has built in optical slave! SU4 Mode

I finally sent Nikon a complaint, because as much as I'd expect myself to buy another speedlight anyways, it's just silly that this flash isn't TTL compatible.

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