Understanding and Using Optical Slaves, Pt. 1

First off, this is a long-overdue post. It arguably could have been in Lighting 101. But this week (four-plus years later) we'll be looking at choosing and using optical slaves.

In this post, how to figure out which kind is right for you.

Only Two Things Matter

Slaves are not particularly complicated. They see a light pulse, and then they complete a circuit -- hopefully firing your second flash in the process.

There are only two variables that should concern you -- connectivity and sensitivity. (Okay, price, maybe. But as you'll see later, it is better to wait a little bit and buy a little further up the scale if you possibly can.)


How sensitive a slave is doesn't mean squat if it will not connect to your flash. Typical connectors are HH (meaning US-style household plug), 1/4" plug, 1/8" (3.5mm) plug, PC plug and specialized connectors such as the weird Vivitar thingie.

There are hot-shoe based slaves, too, but you will always pay a premium for them. Which is why the very first rule of slaves is to:


Sorry for the all caps, but I do not even consider a flash unless it has a built-in slave. But if your flash hasn't got one, you'll have to choose a slave that will connect to it. And God help you if you have a series of flashes with different connectors. With decent slaves starting at north of $50, you can see how the necessary duplication could get expensive fast.

If you have 1/4" and 1/8" jacks on your flashes, you can solve the compatibility problem with a cheap adapter. Ditto getting to an HH jack, if you have a couple bucks and some soldering skills. But the most important point is that you should be considering the down-the-road costs when you are buying flashes. And buying a flash without a built-in slave or an external PC jack makes life complicated for you later.

Long story short, there is a lot of elegance in a flash system with a jack you can sync with low-cost cords and a built-in slave. That was the thinking behind the LP160 -- to duplicate the bigger monoblocs' ease of syncing.


Once you have your slave hooked up to your flash, you are halfway home. Now you have to get it to actually fire.

This is where lots of people pay the newb tax -- when they buy a no-name eBay slave that technically fits their flash but fires about 30% of the time. (But hey! They're $10!)

There are two kinds of slave circuits -- passive and powered. The above eBay specials are almost always passive. And when they do work it will typically be in an indoor situation -- low ambient, lots of bounce surfaces, and for good measure you should probably throw in some pretty high master flash energy levels, too.

Passive slaves will typically advertise a range of ~100 feet. Take that with a grain of salt. It is calculated under ideal circumstances with powerful master flashes.

To be fair, there are decent passive slave designs. But they typically will be for short-range, bright flash situations. My advice is to save a little longer and opt for a powered design.

Trust me, you really want a powered slave. You'd think they'd require batteries -- and they used to. But a while back someone got the bright idea to use the voltage from the flash's trigger circuit to power the slave. Presto, no batts needed.

The range on a powered slave can be very impressive. You'll see advertised ranged of ~600 feet and up. Grain of salt there, too. But you can compare apples to apples from the same manufacturers to see which slaves they consider to be their best.

Take a look at this slave product range from Wein, who has a good reputation for high quality slaves. You'll see a wide range of connectors and sensitivities available.

How do you tell which ones are powered slaves, and thus more sensitive?

You'll see prefixes like "super" and "ultra" being batted about. And the prices will rise, too.

And "super" and "ultra" are not far from the truth. If you have problems with these slaves, it is more likely to be from false positives (random fires). These are likely not random at all, but rather triggers from environmental light pulses -- the sun gleaming off of a passing car, perhaps.

But the takeaway is that an expensive slave is usually worth the money.

Built-In is Better

Here is a photo from a ways back, illustrating just how good the built-in slave is on a Nikon SB-800 when in SU-4 mode.

Built-in slaves (more so the modern ones as opposed to the ones from 20 years ago) are almost always "super slaves." And the internal connectors are all soldered, which is better than any flavor of jack.

That photo was taken in the middle of the day. That flash was triggered by the internal slave seeing the on-camera speedlight. Impressive.

So if you are buying flashes, stick with those models with a well-regarded built-in slave. You'll save money in the long run, and you add a lot of versatility to your lighting schemes.

We'll talk about that -- and how to get the most out of your slave's range and sensitivity -- in Pt. 2.


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Blogger edo said...

Thank you for a informative update. I just like to ask your opinion about using master - slave or remote trigger, in which situation master - slave serves better? Thanks


July 26, 2010 1:17 AM  
Blogger amai911 said...

Thank yo David, when you die you will go to heaven because of this blog

July 26, 2010 3:17 AM  
OpenID focused.ru said...

I have tried many times my SB-800 to fire by a flash of the D70-D90, so it's hard for me to believe you could do that in daylight. Of course, I mostly use i-TTL, not the SU mode — I think, part of light is wasted and the flash does not read the signal completely, and for a simple slave even a small flash is enough

July 26, 2010 5:17 AM  
Blogger Stu said...

Great post! These optical slaves are an excellent way to multiply your flashes without buying extra Pocket Wizards, its also another reason why the Nikon SBs are just so worth the price! They do everything well.

July 26, 2010 10:31 AM  
Blogger Phat Baby Photographer said...

Very informative, even if it makes me hate my Canon flashes even more.

July 26, 2010 11:26 AM  
Blogger Seth Clarke said...

You launched right into the what/how without explaining the why? My experience with slaves has taught me basically to never use them when you could use a trigger instead.

The built-in slave on my Metz flash doesn't seem to fire automatically if it's pointing in the same direction as the camera or firing flash. It mostly only works when you're firing head-on with the slave flash facing the firing flash.

ALSO (and this was why I eventually broke down and bought elinchroms) you can't shoot in manual and use the slave at the same time, so you can't drop the power down to 1/2, 1/4, 1/8 and so on.

SO what's the point? Are these problems unique to Metz?

July 26, 2010 1:25 PM  
Blogger Photography by Diego said...

David, I've had some problems in the past with pre-flashes fooling the optical slaves causing the flashes to fire before exposure. Have you experienced any of that?

July 26, 2010 1:25 PM  
Blogger Shawn said...

What Canon flashes do you have and why do you hate them even more? I usually work with a trio of 580EXII and am happy with how they've worked to date.

July 26, 2010 1:46 PM  
Blogger PhotoInspirations said...

Shouldn't there be a section or at least some comments discussing the "pre-flash" issue? If you are trying to use the pop-up flash as the master, some cameras have no way to turn off the pre-flash (and this includes some rather nice cameras like the 40D).

July 26, 2010 1:55 PM  
Blogger Alex said...

@ focused.ru

Hiya there, well that isn't too strange because it is a totally different system

The i-TTL relies on some really weak short pre-flashes that relay information that is quite precise and detailed!

The slave relies on one single blast of light without any information.

It's like the difference between trying to use morsecode really quickly by making husehed beep sounds or simply shouting the word out loud to the person down the street. The first won't work, the second most probably will.

Just try your slave mode first and then report back if it still isn't working!


July 26, 2010 1:58 PM  
Blogger Scott said...

I'm looking forward to the second installment on this topic. I bought two "high end" Wein optical slaves (the ones with the integrated hot shoe) two years a go and now they do not work. I suspect user-error, but I am not sure what it is I am doing wrong.

Could the level of the batteries in the flash affect the trip point of the slave? Does the optical device age and sensitivity drop over time?

July 26, 2010 2:12 PM  
Blogger Scrivyscriv said...

@ Phat Baby - I know! I bought a Canon 430EX II last year, loved it, then started trying to use it off camera. Now I am ticked off that Canon doesn't put even PC's on their "advanced amateur" flashes! I have a cheapie flash from film days that's worth maybe five bucks - and it has a jack. Why can't my expensive flash have one?

@David - thanks for linking again to that LumPro flash. I dropped one of my manual flashes this weekend and have been looking for a replacement with a recycle time shorter than the 285HV's.

July 26, 2010 2:57 PM  
Blogger Jim said...

After much study and confusion, I'm finally getting comfortable with the ETTL function of my Canon 580EX II, 550EX, and 430EX flashes. But it's pretty obvious that the company really missed the boat by failing to include built-in slaves. Rumors of a "680EX" are showing up on the interweb, and a new model might have that feature. It will probably also cost a whole lot.

July 26, 2010 3:49 PM  
Blogger Charles Verghese said...

Hi David,

I have an off topic question...

I wonder if these optical slaves can be DIY'ed into functioning as a Lightning trigger? Without thinking it out through, I am of the opinion that it could be soldered onto a camera trigger cable.

Reason I am asking is because I am trying to avoid having to pay the big bucks for a traditional lightning trigger.

What is your take?

BTW...I know, I know....you're gonna ask me why a guy in Dubai would be interested in a lightning trigger. Well, it's because the rains come here so rarely and I'd love to capture any thunderstorm passing by....oh yes, we do have 'em here sometimes!!

July 26, 2010 5:38 PM  
Blogger Darren Whitley said...

Can you discuss how to find a slave that will work with electronic flashes? My experiments with attempting to trigger the 580EX with a peanut was a total failure. Slaving a Vivitar was a total success. So it left me having to go to Pocket Wizards, which is a helluva price to pay.

July 26, 2010 9:38 PM  
Blogger Catherine said...

If it wasn't for this blog, lighting would be an even greater mystery than it is now. Thank you, David, for taking the time to explain this stuff.

I recently bought a Canon 580 EX II and have learned from the comments in this thread that it doesn't have a built in slave.

I'd intended to get the Canon 430 EX II in future to use as a second flash, and some Pocket Wizards Plus IIs to trigger them.

If I attach one PW+2 to my hotshoe, and the other to either of the Canon flashes, does this mean that I'd need another PW to attach to the other flash, because the two flashes can't 'talk' to each other?

Sorry for the stupid questions, I'm new! :P

July 27, 2010 6:12 AM  
Blogger Catherine said...

If it wasn't for this blog, lighting would be an even bigger mystery than it is now. Thank you, David, for taking the time to explain this stuff. Now for a beginner's question.

I recently bought a Canon 580 EX II, which I've learned from the comments in this thread doesn't have a built in master/ slave system. I had intended to buy a Canon 430 EX II in the future to use as a second off-camera flash and some (2) Pocket Wizard Plus IIs to trigger them.

Does this mean that after mounting one PW+2 to my hotshoe, and the other to one of the Canon flashes, I'd need another PW to trigger the second flash, because my flashes can't 'talk' to each other?

July 27, 2010 6:18 AM  
Blogger Pixyst said...

@Darren Whitley
I had similar problems initially triggering an SB-800 with a peanut slave until I put the SB-800 into full manual mode.

July 27, 2010 9:48 AM  
Blogger Setcamper said...

Add me to the list of confused with the Canon speedlites. I thought the 580EX II was a master unit and the 430EX II or additional 580's could be used as slaves. It's even shown in a diagram in my 430 manual.

Is that option only available when when the 580EX II is mounted on camera? Can't you use a remote trigger on camera with a receiver on your main off camera (in this case a 580EX II), and then let that trigger the rest of your slaves?

July 27, 2010 11:31 AM  
Blogger Setcamper said...

Add me to the list of confused with the Canon speedlites. I thought the 580EX II was a master unit and the 430EX II or additional 580's could be used as slaves. It's even shown in a diagram in my 430 manual.

Is that option only available when when the 580EX II is mounted on camera? Can't you use a remote trigger on camera with a receiver on your main off camera (in this case a 580EX II), and then let that trigger the rest of your slaves?

July 27, 2010 11:32 AM  
Blogger Darren Whitley said...

@Pixyst, I think there's something about the Canon flashes that resist being triggered by optical triggers. I think it has something to do with how they use a pre-flash for TTL. Changing to manual had no effect on my experiments. They sell optical slaves designed to account for this from what I can tell, but the price deters experimentation. Here's a for instance: http://www.bhphotovideo.com/c/product/263025-REG/Wein_W940040D_HS_XL_D_Hot_Shoe.html


You cannot use the Canon wireless without either an ST-E2 on camera or a master flash on camera. The exception is that the 7D now has a built in trigger for Canon flashes. That's the only camera of Canon that has that AFIK. In other words, a PW triggering a Canon 580EX set as Master won't work to trigger the other light AFIK. You have to be totally propriety with a Canon equipment acting as the master. If you add Radio Poppers, you're only converting Canon proprietary signal to a radio signal. It doesn't change the need for the need to have a Canon flash or ST-E2 as your trigger.

July 27, 2010 11:09 PM  
Blogger jphphotography said...

Hi David sorry to post this here but there doesn't seem to be any other way to reach you.

I was just curious if you've ever covered the topic of insuring your equipment? I just posted an article on my blog about it but I'd really like to here your take on it.

Here's a link to my article if you or anyone else is interested.

July 27, 2010 11:12 PM  
Blogger laird said...

I love the convenience of Wein Peanuts, being small and plug right into Vivitars, but have a unusual problem. I use PW to trigger a SB800, and slave other flashes off that. Sometimes, the Vivitar slave doesn't sync at 1/250 and I have to drop down to 1/160 or slower. Other times they're fine. I use Nikon D300 in manual (not TTL) and no rear-curtain sync. Seems to be unique to Peanuts, as I've not had this happen with "off brand" slaves that slide on the hot shoe. Any ideas?

July 27, 2010 11:58 PM  
Blogger laird said...

David, possible topic: I frequently scout a business location before I shoot. Since there is usually various combos of ugly florescent lights (nowadays with compact bulbs, to boot) I shoot gray cards in various rooms. Back home I use Lightroom to measure the color temp and tint and TRY from that to estimate which filters (in 1/2 steps) to use at each location and which color balance setting (like from the 7 florescent choices on my D300) will give me a relatively realistic image on my LCD. The process is pretty hit and miss even though it would seem to be precise. I don't recall a post on this, and I'm sure we could learn more. Thanks

July 28, 2010 12:15 AM  
Blogger Neil Turner said...

I have a couple of 10 year old Wein ultra sensitive slave units and they are amazing - so amazing that a police car with flashing lights two storeys down in the street set them off! They can also be triggered by a faulty starter in a fluorescent light. Sensitive yes, annoying YESSSSS!


July 28, 2010 5:18 AM  
Blogger midwestphotoexchange said...

Finding a slave that is compatible with YOUR flash can be very very tricky. This is one of those areas where you will be very well served to search the discussion groups on Flickr to find actual user experiences. You can NOT rely on compatibility published by the various slave manufacturers / distributors.

I am yet to find an optical slave that works reliably with Canon flashes. I've tried Fotodiox, several styles of Wein, Dot-line, Nisha and a couple others I can't think of right now. Some of those work some of the time. Some work with some flashes but not with another identical model. If anyone has any recommendations on slaves that work with modern Canon flashes, please email me. Would love to carry them in our store!

Midwest Photo Exchange
moishe @ mpex . com

July 28, 2010 5:37 PM  
Blogger Kevin said...

I just purchased some sonia brand peanuts (I think they are manufactured in India?) I havent tested them outside or at great distances, but they appear to work fine with my 430EX and 580EXII. I have yet to see the odd "reboot" issue with the flashes where they supposedly lock up after each fire and need to be restarted. I found them on flashzebra but purchased quite a bit cheaper on ebay.

July 28, 2010 7:59 PM  
Blogger Kevin said...

One more comment for the canon flash systems...after attempting to trigger my 430Ex from the 580EXII (using canon "IR") which was PC Syned off camera I found out that it can only be accomplished by putting the flash onto a hotshoe adapter...I think it has something to do with the flash thinking it is on the camera.

July 28, 2010 8:02 PM  
Blogger Phat Baby Photographer said...

@Shawn - a number of other folks hit the nail on the head. Canon flashes do not have built in optical triggers. They do have IR communication but the range is limited and the reliability outdoors is dubious at best relative to radio or optical triggers. In general the TTL metering has also been less than stellar in my experience which is my primary gripe with Canon's flash system. That being said, I still get the shots I want, just with a bit more effort and expense.

July 28, 2010 10:53 PM  
Blogger xxberg said...


To be clear - The Canon 580 exII does not have an optical slave. Yes - it can be triggered via wireless eTTL, but not thru simple optical slave. Not quite the same thing.

On the other hand the fully compatible Sigma 530 DG Super of which I have 2 copies includes a very capable optical slave. It has all the features of a 580 ex II + the optical slave. But no external connectors, so you're stuck with the hot shoe.

Optical slaves are not something that I want as I always work in busy environments and I don't want other photographers triggering my flashes.

July 29, 2010 5:17 AM  
OpenID restaurantouring said...

@ Catherine
@ setcamper

If you have a 580EX II flash and a 430 EX flash, you DO NOT need another PW unit to fire them. You may lose some sync speed, but it is still possible. You just have to make sure the 580 is in master mode and the 430 or other Canon flash is in slave mode. I have done this with 2 PW+2's and 4 Canon flashes (all off-camera) in the past before and was decently successful.

Here's how to do it:
1) Set the 580EX II to master mode by holding down the zoom button until the display starts flashing.
2) Rotate the wheel until "Master" is selected (you can also set it to "off" or "slave" in this menu).
3) Set your 430EX flash to slave mode. On my 430EX, it is a simple toggle near the bottom of the flash, by the hot shoe. Not sure if this is the same for the 430EX II.

That's it. You'll want to take some test shots to make sure it works, and maybe decrease your sync speed a little to ensure that both are syncing at the same time. I know that with my old XTi camera body, I had to go as low as 1/125th of a second to get it to sync.

Watch out for your range and try to make sure nothing is blocking the view of the IR windows on the flash units -- the slave unit(s) needs to be more-or-less line-of-sight with the master flash in order for this to work. Have fun with it, and post your results to the Strobist flickr pool!

July 29, 2010 12:47 PM  
OpenID restaurantouring said...

Also, don't get the ST-E2. The PW TT1 and TT5 have made it obsolete.

The PW units are more expensive, yes, but they allow you to do a few things that the ST-E2 / Master 580EX II will never let you do, as follows:

1) sync at a faster speed for more daylight-stopping power
2) High speed sync in a much more efficient way
3) off-camera 2nd curtain sync
4) get crazy range on syncing your flashes

and a bunch more. They're worth it.

- Conway

July 29, 2010 12:50 PM  
Blogger J said...

I've had good and bad experience with Wein peanuts. They can plug right into the vivitar flashes I own, but they have only realiably worked for maybe 30 or so flashes. I had one, that completely crapped out on me after this (I would fire a flash directly at it and it still wouldn't work). The second one crapped out even quicker. After that I said to hell with this and bought another pocketwizard plus II.

August 02, 2010 1:14 AM  

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