Wednesday, July 28, 2010

Understanding Optical Slaves, Pt. 2

Editor's note: There are enough questions coming in via the comments that I am prepping a slave-related Q&A for later this week. If you have a question that has not yet been asked, please get it into the comments ASAP. Thanks.
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In part one, we talked about the differences in optical slaves, and why internal slaves were usually better solutions.

In this post, we'll look at the practical side -- how do you get the best performance out of your slaves?
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#$!%! Thing Didn't Fire!

Slaves are a little like radio remotes in that they are not 100% perfect and reliable. (But the good ones are damn close.)

And unless I am working in an environment alongside other photographers, I almost always use a hard cord or a PocketWizard on one flash (which becomes a "master" flash) and optically slave the others. It's generally very reliable, and a fast way to work.

So, which flash to use as a master and which to slave? The answer might be different than you think.


Power vs. Angle of Coverage

Say you have a key light firing at 1/2 power, and three more accents set at 1/64th power. Try using your most powerful flash as a master and slaving the accent lights. If that main light is gonna be bouncing off of all sorts of things, so much the better.

But if you are running flashes at only modest power levels, you might try using the flash with the widest beam spread as the master flash. Often, beam spread trumps power level as the reason for a flash to be the master. The reason is simple -- the other flashes have to be able to see the light from the master to fire.

For example:


In this instance I would use the umbrella fill flash as a master, even though it is gonna be at a lower power than the key light. Reason being, the umbrella light will go out in all directions and the other flashes will see it better than if I master sync'd the key light at bottom right.

On the other hand, if I used one of the other flashes as a master, the umbrella flash might not fire. This could happen either because of the limited beam spread of the other flashes, or because the umbrella itself was shading this flash and reducing the intensity of the light from the master flash before it reached the slave.


The More, The Merrier

Realistically, with as many flashes in a photo as in the above example, they will usually all fire no matter what.


As long as at least one slaved flash can see the master, it will likely set off at least one other slaved flash, and so on. This cascading effect means that it is actually easier to fire off of a room full of 50 slaved flashes than it is to fire, say, two.

In the Usual Suspects -style photo above (more here) there was a 2-stop down umbrella right at the camera, acting as an on-axis fill. Those slaved, low-powered accent lights were fired by the umbrella. And if they weren't, one of the many other accent lights took care of the problem for us.


Be Like McNally

Knowing how to choose your master/slave flashes correctly is a good skill to have for those of you who use Nikon CLS or Canon eTTL syncing methods, too.

One trick Joe uses for complicated setups is to use an off-camera TTL cord and hang that master flash out somewhere where all of the remote/slave flashes can better see it. There is usually a spot that will get the job done -- and often that spot is not right on top of your camera.

But you can think that way for manual-flash slave setups, too.



For instance, if you had one PW and several slaved flashes that were gonna be used as gridded key lights, you might remote-/hard-sync a background/scener/rim light (upper left) that all of the gridded flashes' slaves could see. Problem solved.

And this is an instance where the slaved flashes' rotating heads would come in handy, too. You can point the heads at your subjects and rotate the bodies of the flashes so the slaves can see the master flash. (That is why near-360-degree rotation on flash heads is so useful.)


Hiding the Sun

Sometimes the problem is that the ambient light level is very bright, causing difficulty for the slave. It has to see that pulse of light to fire your flash. And if the slave eye can actually see the sun, too, that's a lot of competition.



Shading your flash eye with a little gaffer's tape will make a big difference in the range of your slaves in daylight. Just make sure you shade the sun while leaving a clean line of sight to the master flash.


It's Firing By Itself

If your slave is so sensitive it is getting false fires (assuming it is not a total piece of crap that would false fire inside of a dark closet) that is an easy problem to fix, too.

You can "dumb down" a slave by partially covering the eye with tape until the offending false positive trigger is canceled but your master will still fire the slave. With "super" and "ultra" slaves, you might have to do this more often than you would expect. No big mystery -- they are just that good.


What's Your Favorite Slave Tip?

Do you have a favorite slave tip I left out? Do you know a great slave that doesn't break the bank?

Hit us with a comment (and/or a URL to a picture that proves how good your "giant killer" cheap slave is) in the comments.


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33 Comments:

Blogger Elysian Photography said...

One really successful thing I've managed to do on a budget with fully manual, no-slave-included flashed (I use three now-discontinued Sunpak Super 383 Autos as portable strobes) is to simply place an optical trigger on a sync cable. My models, the Kaiser economy triggers, have a dumb hot shoe which basically just triggers the dang thing. Stick a dumb hot-shoe to hotshoe (or whatever your flash will take), and you can reposition the master/slave combo just about any which way you can imagine. The trick works really well with line of sight triggers which need to fire, well, outside line of sight. Won't get you the PW range, but it's pretty damn near perfect in reliability and near indestructibility. Then all you need is one radio trigger set and you're done.

July 28, 2010 5:53 PM  
Blogger Raymond St Arnaud said...

These slaves for Canon flashes have worked for me and are reasonably priced.
http://www.flashzebra.com/opticalslaves/index.shtml

July 28, 2010 6:07 PM  
Blogger supergimp said...

I use the "Extended Range Version" optical slave that FlashZebra sells (available in various jack configurations) and have never felt them to be flaky or unreliable. Sure I have to sometime shade them or watch for false triggers and deal with that, but they work really well. I use them with (here we go...) FZ's hot shoe adapters on my SB600's because I got the 600's cheap and love the versatility to go McNally with CLS AWL with them if I want. It's worth the erector-set approach to me.

July 28, 2010 8:18 PM  
OpenID danielhoherd said...

Is it possible to use these same optical triggering techniques to fire off multiple cameras?

July 28, 2010 9:18 PM  
OpenID iainisbald said...

Talking about false firing, I shot a gig for a band a while ago with my SB-800 in SU-4 mode. It worked a treat, but when the stage strobe came on, flashing about 3-4 times a second, the poor wee SB-800 was firing as fast as it could in response.

July 28, 2010 9:19 PM  
Blogger edo said...

Interesting post,especially on which one is becoming the master.

Is it ok to use PW in master flash & trigger the slave using the master? Are we goin to have synch issue? Thank you

www.motoyuk.com

July 28, 2010 9:41 PM  
OpenID outofnapkins said...

I have run across the "standard" h-prong connector on the wein slaves before (back in my old medium format film days. I had inherited a sync cord for it but didn't know what it went to until today. For the life of me, I can't figure out when you could use one of those today without that dang cord. Would you mind including a section on the various slave connectors and when and how to select the best option/type.

July 28, 2010 10:38 PM  
Blogger ethervibes said...

Has anyone tried opening the YN-460 and taken out the optical slave positioned in the flash-head (what a bummer) and repositioned in the red-plastic area (mock-eye). Thanks

July 28, 2010 11:56 PM  
Blogger DrMuz said...

I was having problems synching my canon flashes via optical triggers until I figured out how to turn off the pre flash, now all is well.

July 28, 2010 11:59 PM  
OpenID Mark said...

in some cases, instead of pointing the flash sensor to see the triggering flash, I point is to the subject.

Hopefully the sensor will pick up the light bouncing from the subject and be enough to fire it.

Especially useful when using optical remotes outdoors with nothing to bounce with.

July 29, 2010 12:04 AM  
Blogger Scott said...

I second the sync question posed by edo. What kind of sync speed can you expect when optically firing flashes? Also, if you have a setup with cascaded slaves, how much of a hit does your sync speed take?

July 29, 2010 12:13 AM  
Blogger Boucman said...

A trick I have used a couple of time to be able to use my on-camera flash with off-camera flashes was to use my optical slave (with hot-shoe) to trigger my cactus remote.

I put the cactus transmitter on the optical slave, and the combo right next to the camera's flash. Since the OS is right next to the flash, the combo triggers really well and I can use my on-camera as an extra fill when I'm short on strobes...

July 29, 2010 3:17 AM  
Blogger Stefan said...

Hey Dave,
i think one thing wich wasn`t told for using the build in slave of some falshes is to be aware that some flashes can take a meassuringflash some cant an will fire to early and some will only work with meassuringflash (Nissin Di662 for an example). So in that case you wont be able to fire one of those Di662 with an of-cam-flash exept you use a TTL-cord or a pricey trigger wich can transmit TTL. (PW or Photix Atlas as example)

So one thing you have to watch is that the flash you`re going to buy can do both. It nearly had driven me crazy as i was trying my new bought Nissin and in the next moment I discoverde the flash for canon wasn't even able to be triggert on the centrecontact on the flashfoot so way to trigger by an radiotrigger, an opticalslave-hotshoe or even by a syncshoeadapter. Payed my noobtax on that. Now looking for 2 Lumopro 160 here in europe.

July 29, 2010 5:16 AM  
Blogger Ad said...

When shooting with optical slaves or CLS in cavernous environments which are tricky to get the slaves to fire (gymnasiums, theatre) I aim the flash forward on the light standard and place an umbrella behind it to act as a surface to bounce the pw'ed flash master off. The umbrella is not used to soften the light, its simply used to catch and reflect back the master onto the slaved light.

July 29, 2010 5:36 AM  
Blogger Matt said...

I've found that florescent lights' flickering can cause some super-sensitive optical slaves to trigger. If I can't kill them, I use a similar technique as in bright sun. It does the trick.

The lesson, as always, florescent lights is the devil.

July 29, 2010 9:33 AM  
Blogger Jim said...

I used to take event photos with a "strobe-on-a-stick," a SunPak 383 with a curly synch cord and a couple PC-to-PC junctions. Reliability was spotty at best, although multiple rubber bands around the dreaded PC connecters made a moderate improvement.

Now I use a FlashZebra 0128 adapter and their Sonia 0073 slave. For a trigger, I use the pop-up flash on my Pentax K20-D. I kill the pre-flash by using a fully manual lens (usually a 28mm). The 383 (and my backup SunPak 422) both rotate, allowing me to place the slave so it always points at the built-in while pointing the flash tube at the subject. Works great.

July 29, 2010 11:52 AM  
Blogger ethervibes said...

Thanks to Boucman for sharing the trick of coupling an optical slave and a cactus transmitter. Is there a way to attach an optical slave to the Yongnuo RF-602 transmitter so that I can use my on-camera flash as a fill. I have ordered the RF-602 and hoping it shows up in couple of weeks. Thanks

July 29, 2010 12:51 PM  
Blogger TWHunt said...

How about slaves that handle pre-pulses for TTL, Nikon's CLS, etc?

I like to use an SB-600 with CLS so I can adjust the power from my Nikon body. Are there good slaves that will ignore the pre-pulses and fire at the right time?

July 29, 2010 12:52 PM  
OpenID restaurantouring said...

@ Scott
@ edo

From my experience, you may occasionally experience synch issues, which are easily remedied by slowing down the sync speed a notch.

It varies from camera to camera, flash to flash, and sync methods.

e.g. If I use my old Canon XTi camera, I have to stop down to 1/125th of a second to sync a PW+II connected to a master 580EX II (via the female hotshoe to miniphone cable / adapter) that is triggering a slaved 430EX

BUT, if I switch to my 5D mark II, I can still sync at 1/200th of a second.

Not sure why this is.

I have also used a Nikon D40 with a LumoPro LP 120. When it is hard-wired using a miniphone to miniphone cable and a hotshoe adapter, I actually get a FASTER sync speed than the native sync advertised on the D40 -- which is awesome. When I use the optical slave + the pop up flash on the D40, I get 1/200. Not bad.

So, it depends. Check it out.

July 29, 2010 1:11 PM  
Blogger Logan365 said...

ttl preflash will set off your slaves making it look like your slaved flashes never fired.

July 29, 2010 1:12 PM  
Blogger Mitchel said...

Great article--both parts. I'd love to be able to mix slaving a couple of flashes pointed at a backdrop and at the same time use TTL for the key and fill flashes. However the pre-flashes (either visible or IR) of the hotshoe commander (Canon) set off the slaves, which don't recover in time to flash with the shutter. Aside from investing in PW's new TTL devices, are there slaves that resist pre-flashes?

July 29, 2010 1:13 PM  
Blogger Nick said...

re: Slaves that resist pre-flashes.

I recently purchased several Yongnuo YN460-IIs, and have been very happy with them. ($40 each on ebay)

Their built-in optical slaving is sensitive enough for my needs, and seems reliable enough. They offer two slave modes, one which ignores TTL preflashes.

From what I've read, the original YN460 had some reliability concerns, but I haven't heard similar comments about the YN460-II ... yet.

July 29, 2010 3:38 PM  
Blogger Joey (aka Pepe) said...

This is the geek in me taking over... ¿do you know of any measurements concerning reaction times for these optical slaves? I'd like to have an idea of the delay introduced if you were to daisy-chain these things. Also, my very limited (and possibly flawed!) testing with the LP160 didn't show any noticeable difference when using the optical slave in "normal" mode v/s "ignore TTL" mode, while using my 430 EXII in ETTL mode to trigger it.

July 29, 2010 5:43 PM  
Blogger dominique said...

Sometimes if I can't get the optical slave on the back of my White Lightning monoblocs pointing in the right direction I use a piece of paper tented and taped to the back of the light to reflect the key flash onto the optical slave.

July 30, 2010 6:01 PM  
Blogger craig said...

The only time we use slaves is in tightly controlled studio situations. Outdoors they're just unreliable - not enough bounce to set them off, or competing with the sun. Even with good slaves, there's no getting around those issues with the reliability of radios. Even in the studio, we're often using snoots and grids exclusively - slaves don't work well in that.

Even indoors you have things like flickering fluorescents that will set them off unreliably. Or, in industrial situations, the rotating strobes on things like forklifts and other heavy equipment will set them off.

All in all, we pretty much use pocketwizards on all location shoots as it saves a hell of a lot of time in figuring out 'will the slave work here?'

July 30, 2010 7:21 PM  
Blogger Stu said...

I've got a bunch of Nissin speedlights that I use with Nikon sb-800s . (The Nissins won't fire with Pocket wizards, no plug, hotshoes with pc plugs don't worth either, Nissin told me its impossible. So stuck with optical). The optical slaves all works fine if you're spraying light all over the place, with softboxes, umbrellas and stuff. But when you control the light with grids and snoots, the opticals won't fire. Does anyone out there have some special tricks to deal with this?

July 31, 2010 11:06 AM  
Blogger felix said...

TWHunt said...
"Nikon's CLS, etc?
Are there good slaves that will ignore the pre-pulses and fire at the right time?"

These work well with Nikon CLS and ignore the pre-flashes - they are very cheaply engineered but I haven't had one mis-fire or break yet:

http://www.bhphotovideo.com/c/product/634996-REG/Morris_11101_DS_1_Digital_Slave_Trigger.html

July 31, 2010 11:54 AM  
Blogger PHOTOMAMP said...

Hi,

I work usually with CLS system.
I use 1 - 4 flashes, but only 2 of them are iTTL (CLS compatible). The other two (SB25 and SB26) are triggered by optical slaves (the integrated one in the SB26 -works great!- and one external by METZ -old one, by the way, but great as well- with the SB25).
When I need more than 2 lights, I place the optical slaves where they can see the light of the CLS flashes, but not the preflash (in order to avoid they trigger withthe preflash).
Only as an example, in a clamshell lighting setup, I shot nearly between the clamsell; rim lights are CLS and frontal ones lights (the clamshell itself) optical slaved.

And of course, great post! (as usual :)

Regards,

Miguel
www.photomamp.com

August 01, 2010 5:16 AM  
Blogger Schorschi said...

I use an optical cube with hotshoe in combination with my YN RF-602 wireless triggers to set off off-camera flashes.

My camera's pop-up flash is used to trigger the optical cube that sits right in front of it on-camera, which in turn wirelessly fires off-camera flashes.

Works without problems. The reason I'm doing this is, because my camera, when set to burst mode disables the camera hotshoe.

My RF-602 has no problem coping with the burst rate of 7fps.

August 01, 2010 11:45 PM  
Blogger Greg said...

I bought three Wein peanut slaves, and was using them with some Vivitar 285hvs, from 5 feet away, and I found they only worked about one time in 10. I got rid of them and went to pocketwizards.

August 03, 2010 1:44 AM  
Blogger Martin Smith said...

@Boucman - Sync speed won't take a noticeable hit. We're talking speed of light here :)

August 03, 2010 8:08 AM  
Blogger Stuart Mackenzie said...

Just in case there are any Canon shooters here..

Syl Arena has just done an article which details the use of Optical Slaves with Canon Flash ( you need the right optical slave)

http://speedliting.com/how-to/canon-speedlites-optical-slaves/

August 10, 2010 3:57 AM  
Blogger PHOTOMAMP said...

Hi David and fellow strobist readers!

Just to let you know I have added a link to this article in my lighting blog.
I have linked this entry, in the context of a wide article talking about how many ways we have to trigger flashes disconnected from the camera (cords, optical slaves, radio triggers, TTL proprietary wireless systems).
Please, if there is any problem linking this entry, just let me know and I will deleted asap.
Thanks so much and, of course, congratulations for your work: great as usual :)
Warm regards,

Miguel
www.photomamp.com

August 17, 2010 5:04 AM  

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