Q&A: How to Use Your Nikon SB-900 in Optical Slave Mode

As most of you know, the discontinued Nikon SB-800 speedlight has an awesome -- yet, oddly undocumented -- built-in slave. But given the questions I have gotten recently, many people who own the newer SB-900s are not aware that their flash has the same capability.

A walk-thru on how to access and use the built-in slave in your Nikon SB-900 speedlight, and how to get better results from any slave outdoors, inside.

SU-4 Mode Button Sequence

SU-4 mode is a legacy TTL mode which existed long before Nikon's CLS system. Props to Nikon for continuing to include it. And the day they stop including it is the day I start hoarding old flashes.

By setting your flash into both manual and SU-4 modes, as they say, dis where da magic happen.

Here's how to do it.

1. Press the "OK" button until you see a custom function menu appear. Should take a couple of seconds.

2. Using the command dial, scroll until you get to "SU-4" mode, and press "OK".

3. Use the same dial. scroll to "on." Press "OK" again.

4. Press "Exit" to get out of the menu.

5. Set your selector switch to "Remote".

You are now in SU-4 slaved mode, but you flash may be in either Manual or Automatic firing mode. You almost certainly want Manual mode. Use the "mode" button to get to "M" (or manual) mode.

Now your flash is in manual mode, and set to fire when it sees another flash. You can adjust the power level in manual mode the same way you do it if you were not in SU-4 mode.

Tips on Usage

The slave eye is just below the battery door, and is seen as a small, bright circle in the photo at left. You need to position your flash to where the head points where you want, and the eye points toward the flash which will trip this flash.

(That's why the 180-degree rotation feature is valuable on the SB-900, and why you may want to add the same feature to your SB-800.)

If you read the SB-800 SU-4 tutorial, you know just how good this slave is. I count on them all the time, and they rarely let me down. If I am shooting in a room with all SB-800s, I will usually only take one set of PWs and slave the other flashes. They rock.

Here is how you can improve your already good results when shooting outside.

When you get a misfire, the problem is usually that the slave eye window was seeing bright sun in addition to your other flash's pop. This is easy to fix.

Once you get your lights set, use some gaffer's tape and make a little "porch roof" for your slave eye that will shade the sun but not block the view to the flash being used to trip this one. Your percentages will increase dramatically.

And, Speaking of Master Flash

One common mistake when using SB-800s or SB-900s in SU-4 mode (or any other flash with a good slave, for that matter) is not taking into account any "preflashes" that may be happening before your main exposure.

These slaves are so good they will almost certainly see and preflashes from the master flash and trip your slaved flash, too. And this all happens just a few milliseconds before your exposure, so the flash does not have time to recharge and pop again when you want it to.

The fix is easy -- make sure your "master" flash is not set to "master" mode, which enables a series of TTL-measuring TTL preflashes. You want all flashes in manual, where they will issue just one, pre-set pop. This way all of your flashes will sync together, and exactly when you want.

As long as everything is set to manual, your secondary flash is set to SU-4 mode and the slave eye can see your other flash, you will be amazed at how well it all works together.

And you might even feel good about how much coin you dropped on that spiffy new Nikon SB-900 speedlight.


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Blogger Jim Felder said...

OK, so if I'm using 2 or 3 nikons in TTL mode and using my built in flash as a commander. Then I have 1 or 2 older non dedicated flashes attached to optical slaves. Those slaves will fire when my built-in flash fires correct? So it's either go manual all the way or don't use the optical slaves?

March 11, 2010 12:34 AM  
OpenID Richard Clary said...

Mr. Hobby, nice reminder. I just did the rotation enable cut on another new SB-800 I got from a guy at work WHO NEVER USED IT! I was at the Paso Robles Workshop. I have a magazine to send you that is not general circulation (concerning photo work you taught) that might be nice to see. I also may have an upcoming ride on a C-5 Galaxy. Probably some good things to share from there too... If you will send me an email or reply to this I would like to share some things. Yes, I will finally break down for an SB-900.

March 11, 2010 1:23 AM  
Blogger sulayman said...

Maybe it's just late (and I'm almost embarrassed to ask this), but ... what exactly is the difference between slave more and the remote mode that you can just flip the switch to?

Is it that slave is triggered by flash (and therefore triggerable by most cameras) and remote is triggered by IR?

March 11, 2010 1:29 AM  
Blogger David said...

Hey, Richard-

Of course I remember you from the Paso Robls class... Kinda hard for me to get in touch with you if you do not leave contact info!

Leave your email addy in a DO NOT PUBLISH comment and I can ping you back. But preferably leave it next week, as I am in the Middle East right now, with limited net time and access.

March 11, 2010 1:41 AM  
Blogger NorCalScan said...

My brother and his gf have gone to canon leaving me and my d70 and sb800 in the dust for "sharing". Until I found su-4. Now I attend some weddings they shoot and just bring my 800 along for the added light. They've never worked with more than one light so after seeing some basic strobist action in their shots they're hooked. I just wish their speedlights did the same for me. I think my wallet will have to spend for some PW anyway.

March 11, 2010 1:51 AM  
OpenID stephenzeller said...


The "Remote" position on your SB900 will put your flash into the Creative Lighting System (CLS) Remote mode so that it will receive iTTL information via the Master flash, which is either your pop-up flash (D70, D80, D90, D200, D300, D700, etc.) or another SB800 or SB900 in your camera's hot shoe.

SU-4 or "slave" mode allows your flash to be triggered by any other type of flash (non-Nikon flash, studio strobe, any pop-up flash). It also means that other photographers near you who are using a flash can trigger your flash as well, because the optical sensor looks for a contrast in light. This is also why the bright sun makes it sometimes difficult to trigger a flash in SU-4 because of the lack of contrast, thus David's mention of using gaffer's tape to create a bit of shade for the optical sensor.

Hope that helps answer your question.


March 11, 2010 2:24 AM  
OpenID Tzed250 said...

I use my SB-900 with my SB-80DX , which also has the the built in slave. They work great together!

March 11, 2010 6:35 AM  
Blogger Barnacle said...

when using both my sb800 and sb26 together, i usually use the sb26 as the slave with good results. it's a great feature!

March 11, 2010 8:25 AM  
Blogger Reinoud said...

Thanks for the tip! I searched for the optical slave setting almost 10 minutes last week without succes, so I had to think up another light setting.

March 11, 2010 9:27 AM  
Blogger Steven W. Seal Photography said...

I use the SU-4 mode on my SB-800s quite a lot. It works very well as long as there are no other photogs around shooting with flash. I usually leave them set in SU-4 mode even when using sync cords because it has an optional beep that is only available when the unit is in remote mode. It will sound when the flash has recharged. I find that very helpful.

Apparently lots of photogs out there are unaware of this feature. A while back, I was working with some of the creative folks from our corporate office who were shooting employee photos for the company’s web site. They were shooting with a three head Novatron set up and had a couple of SB-800s in their kit. The Photog grabbed one and looked at me and said “You have a couple of these, right? I sure wish there was some way to work one of them into this shot”. Needless to say I was an instant hero. Thanks DH!


March 11, 2010 10:14 AM  
Blogger Myron said...

Mostly you manuel guy's use the SU-4 mode as a manuel slave but the SU-4 stand alone is a TLL slave. Not that we really read the book but what do you suggest for us lazy auto TLL guys, or how else can we use the SU-4 mode?

March 11, 2010 1:29 PM  
Blogger kaina said...

That's very interesting! It made me wonder though: does anyone know if the Minolta 5400 HS has the same kind of capabilities? I now shoot Nikon, but a long time ago, I used to shoot Minolta, and I bought this 5400 HS strobe. I still have it, it (hopefully) still works, but I don't have money enough to buy PWs. So if there was a trick to slave the Minolta, I'd have a third flash to play with!

March 11, 2010 2:07 PM  
Blogger JODY said...

I love the SU-4 mode. Makes my life easier at times. I just can't get the bugger to work at full power. 1/2 power and below it syncs great at 1/200 on my D80. At 1/1 I can't get it to trip even at 1/30. All in all it's a great addition, and my problem is most likely user error.


March 11, 2010 3:54 PM  
Blogger Steve said...

I use this mode on my SB-80DX as well. I wish I had an SB-900 but I instead bought a couple of SB-600 flashes which don't appear to support SU-4 mode.

Am I missing some hidden menu item?

March 11, 2010 10:14 PM  
Blogger Hao Phung said...

does it work with high speed sync?

March 11, 2010 11:50 PM  
Blogger Bradley said...

Shame on Canon!! Again, Nikon shows that they are better engineered; I shoot Canon because I like the camera feel - but more simple engineering items (optical slave, pc socket, etc.) that do not show on Canon's $430 580EXii are frustrating as a Strobist.

March 12, 2010 1:07 AM  
Blogger JAC said...

How does the 'Nikon SU-4 Wireless Slave Flash Controller' compare?

Seems a relatively cheap way to turn an old flash into an SU-4 remote.

March 12, 2010 2:55 AM  
Blogger Bernhard A S said...

Thanks for the very useful post of the undocumented feature.

I am currently testing a Chinese DP1 Cell from Adorama. It promises to work with "preflash" and has a switch for "normal" and "preflash".

Strangely enough it seems to be working with an SB-900 and the Metz 54-4i with CLS as "Commanders" . However it did not fire correct with the SB-800???

Will need more testing.

Also David wrote: "And the day they stop including it is the day I start hoarding old flashes."

I thought you do that already?


March 12, 2010 5:12 AM  
Blogger sfbroome said...

I, too, use SU-4 quite a bit, but I'm confused about the "undocumented" part. It's covered on pages 84-88 of the SB-800 manual, which is where I first learned of it. Thanks for all of your incredibly instructive info on flash, David. I hope you come to Orlando again for another seminar.

March 12, 2010 6:47 AM  
Blogger David said...


They document it, but that section explains it as if all flashes need to be in SU-4 mode to work together. That is because SU-4 signals both a "start" and "stop" signal for the flash, which means you can add add'l auto flash units.

As long as you are not concerned with the "stop" command, you can use it as a slave for amy light. That triggering light does not have to be set to "master," or SU-4 or anything.

So yeah, you are right, it is there. But it is incomplete and confusing, IMO.


March 12, 2010 7:04 AM  
Blogger sfbroome said...

Thanks, David. I wasn't aware of the "start" and "stop" signal.


March 12, 2010 7:38 AM  
Blogger David said...

It's nothing fancy AFAIK, just a simple quench pin signal. Kinda like the RadioPopper does it, except for that the slaved SU-4 flash matches the pulse duration of the master.

Not foolproof in it's original mode/purpose, but pretty slick for how simple the electronics are.

March 12, 2010 8:12 AM  
Blogger anhesty said...

great post. i have an SB800 and the slave mode is awesome.

March 12, 2010 2:30 PM  
Blogger Sodabowski said...

@ kaina

You can buy standalone optical slaves (hotshoe mounted) for a few bucks on ebay, works with any hotshoe strobe. They're such a blast (... sry).

March 12, 2010 5:57 PM  
Blogger Azzurri said...

Hey Dave,

Do you know when you are gonna test the new pocket wizards for Nikon? are you going to get any beta versions?

March 13, 2010 2:42 AM  
Blogger Aaron Linsdau said...

I use the SU-4 option all the time. Many times the CLS won't fire off when the flash is too far away but sometimes the SU-4 will pop when the flash is around the corner. It's very handy.

March 13, 2010 10:44 AM  
Blogger M said...

Just a small correction to Bradley @1:07am, the Canon 580EXii does indeed have a sync socket. As to the cost, when I'm not using PW's I use a Metz Mecalux 11 optical slave, together with the strobe was about $420...although I think the price may have increased as Canon gear has all shot up in the last year.

Anyway a SB900 is currently $450, a 580EXII is $420 and an cheap optical slave is about $15 (all prices from B&H) so yes, it would be nice for the Canon to have the functionality built-in but it isn't really worth a rant.

March 13, 2010 10:44 AM  
Blogger Heipel said...

This is, as always, darn useful information.

And, omg, there's actually a video of a PW mini working with a D3 and SB900 on the PW site! Still sounds like it'll be 2011 before we see general production models available.

March 13, 2010 5:41 PM  
Blogger Patrick said...

Ah horrible version of the SB800 mod video shows up again! David, we have updated that video because everyone complained about how loud the music was. There is a much better video on our fstoppers.com site but you can also watch it here: http://vimeo.com/9918355

I still think the SB800 is superior to the SB900 in everyway except the battery door and the refresh rate. Oh well, Nikon cannot get it right EVERY time :) Hope Dubai was good...are you back?

March 13, 2010 8:28 PM  
Blogger Nina said...

Thanks for this post. I have the SB-900 and am still working on perfecting my techniques with it.

March 14, 2010 11:06 AM  
Blogger Aly-Rae said...

I am indebted to you for life!
Bought this thing almost a year ago and the thing is still an enigma to me and we've had several heated discussions over the past year about how I HATE change.
You've brought me one step closer to not regretting the purchase.

March 14, 2010 3:18 PM  
Blogger Colin Ross said...

Is there a way to set the flash to go onto standby mode in SU-4 mode? And if so, how do you 'wake it up' again?

March 15, 2010 10:54 AM  
Blogger Stewbphoto said...

Not Happy to hear that Nikon is discontinuing the SB-800... I refuse to pay $500 for a strobe.

March 15, 2010 11:45 PM  
Blogger Steven said...

@colin ross

There are settings to change the "standby" timeout on the SB-800. I assume the SB-900 works the same way.

I set mine to never go into standby mode. Then I don't have to worry about waking them back up.

however, if they do go to sleep - any flash trigger (from the slave or the hotshoe) should wake up the flash. Bad part about that is you lose that frame on your camera.

March 16, 2010 11:40 PM  
Blogger Luis said...

@Jim Felder

You can try this that works with my cheapo optical slave from ebay and my Sony Alpha camera and flash. I don't know if Nikon flashes work in the same way, but the Sony(and I guess, Minolta) only use the infra-red component of the light emitted by the master flash for getting instructions and the optical slave only uses visible light. So, I put over my built-in flash a filter that lets infra-red light to pass but blocks visible (a few layers of blank developed negative film works). In this way, my sony flash can get the orders from the camera and the slave is only triggered when this finally fires.

March 18, 2010 8:36 AM  
Blogger CAR said...

So, I'm in the studio this am shooting a huge wedding cake - and the client wants some texture in the background. A couple of SB800's and some foam core later - viola! BUT How to trigger them in sync?? Well su-4 mode of course! Worked perfectly!!

March 22, 2010 3:39 PM  
Blogger PhilScott said...

I too have a Minolta 5400HS flash lying around from my Maxxum 7 35mm days. I haven't tried it yet with an optical trigger but i think I will. I have an SB-900 and 3 x SB-800 and being able to add a 5th remote light when shooting architecture would be cool.
Let us know if you try it.

March 23, 2010 3:46 PM  
Blogger Yvonne Jordaan said...

I find it difficult to re-size my photographs. Is there a software program you can recommend? I am not that computer literate and need something very user friendly.
Thank you

April 08, 2010 3:43 PM  
Blogger Morten said...


I am confused.
You say we must not set the "master" into Master on the SB 900.
But if I do not, the room where I put the slave stays dark. (The slave do lighten, but in a small amount). As soon I set the masterblitz to master, then the second room lightens up in the way I want.

Please enlighten me.


September 03, 2010 2:04 AM  
OpenID Alinake said...

I use SU-4 a lot on my SB900, but this weekend I found myself in a strange situation. For a particular reason, I had to use the SB900 in SU-4 and also sited on a wireless receiver. One photographer would use it optical, the other wireless. While the SB-800 trigger in both modes at the same time, the SB-900 wont trigger by wireless if in Remote and SU-4 mode :(

Did any of you found an workaround on this?

November 05, 2010 3:49 AM  
Blogger Tim said...

I have come accross a slight problem using an sb-900 in slave mode. I would like to use it with two 580 ex-11's. I am firing the 580's via the infra-red ST-E2. This fires them fine - however, when I add an sb900 in slave mode, it fires but the 580's do not. Wondering if anyone has had this problem or knows a solution?

January 24, 2011 9:21 AM  
Blogger Nadz said...

does this will work on SB-900 and SB-600?

June 16, 2011 11:18 AM  
Blogger sarskaggs said...

I just bought the flash sb 900 for my Nikon. I'm trying to use the flash off of the camera on the remote setting. It will not flash off camera. What am I not doing right? Thank you!

July 18, 2011 2:55 PM  
Blogger Boni de Castellane said...

How do I manage to set the Nikon SB-600, so it goes off when I use mi 1/64 flash on a Olympus XZ1. If I set the SB-600 to remote, it just does not work :(.

September 24, 2011 10:26 PM  
Blogger Boni de Castellane said...

How can I trigger the Nikon SB-600 flash to go off, with a external flash? I already did set it to remote, but it just does not work :(.
When there is a flash by the XZ1, the SB-600 does not do anything.

September 24, 2011 10:28 PM  
Blogger Jackie Simpson said...

I use my Nikon sb-900 off camera with pocket wizards on my Nikon d5000 I was wondering if my sb-900 will beable to fire off instudio strobes.

March 14, 2012 11:07 PM  
Blogger Rob Pruitt said...

Thank you SOOO much, I've been looking everywhere for how to do with with my SB-900. You are awesome!

April 25, 2012 11:39 PM  

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