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Canon Wireless Quick Start Guide
Hi, and welcome to this guide that hopefully allows you to get started with the Canon Wireless system without delving too deep into the technicalities of this subject. There are many good websites on the Canon flash system, but I haven't seen a single summary that allows you to get started easily on what you need and how it works, so here's my attempt. I won't explain to you every little setting you can make or how you can do these settings, look in your flash manual for these. I also won't go into detail on every device that may or may not work with this system, as I'm simply not familiar with them all (I have a 420EX, 430EX and 550EX). But I'll do my best to give a roundup that may just get you started.
What is Canon Wireless?
It is a system that allows you to use a master and one or more slaves to control your lights (Canon Speedlites). These devices communicate optically, with visible light when you use a flash as a master, or with infrared if you use a ST-E2 as your master. When you fully press the shutter the master sends a coded optical signal that tells the slaves to fire, and they all do so as soon as the shutter is fully open.
E-TTL
Canon Wireless allows you to use E-TTL (Evaluative Through The Lens), which is a system where the flash first does a so called preflash, and the camera then measures the reflected light from the scene. If it sees too much light it'll decrease the flash output, if it sees too little light it'll increase the flash output. In a Canon Wireless setup with multiple groups [more on groups later] the master device will tell each flash group to fire in a rapid sequence, and set each group's output based on these metering results. This sequence of preflashes and metering happens so quickly that the human eye is generally only able to see a single flash, but an optical trigger would react on the preflashes and fire too soon. If you want to use an optical trigger along with an E-TTL system you'll have to use an optical trigger that can ignore the preflashes and only react on the main flash.
What do you need for Canon Wireless?
You need a master, and one or more slaves. As a master you can use the ST-E2 transmitter, or a 550EX, 580EX or 580EXII speedlite. As slaves you can use any of the 420EX, 430EX, 550EX, 580EX and 580EXII (there might be a couple more Canon models that work, but I know these to be working at least). Note that there are also the Sigma EF-530 DG Super flashes that are supposedly compatible with the Canon Wireless system [both as master and slaves] and they're a bit cheaper than Canon Speedlites, but I've read mixed reports on their compatibility. I also have no first hand experience with these, so I won't make further references to these. They should work in theory, but I would recommend second hand Canon flashes if your budget is a problem.
Disadvantages of Canon Wireless
For one, the price. Canon Speedlites can be rather expensive. Also, the range and line of sight reliance could be a problem depending on your needs. For the ST-E2 the range is specified by Canon as: "Indoors: Approx. 12-15 m/39.4 - 49.2 ft; Outdoors: Approx. 8-10 m/ 26.2-32.8 ft" (550EX or 580EX flashes have about the same range specification). And then there is the problem that outdoors light doesn't bounce around too well. Indoors the system works great, light simply bounces around almost everything and you don't really have to use line of sight from master to slave. But outdoors you need a direct line of sight between master and slave, and direct sunlight can confuse the sensor on the slave. You need to shade its sensor or the slave won't fire, and you need to have the sensor aimed at the master. The sensor is the little dark thingy on the front of your flash (not the large red area, that's the AF assist beam).
Advantages of Canon Wireless
You get full E-TTL. This means that you are able to use High Speed Sync that allows you to go above the normal flash sync speed of your camera (usually 1/200s or 1/250s) though this will reduce the maximum flash output as well, and with E-TTL your flash output will automatically adjust when your lighting conditions change. In a studio you have full control over your light, but at an event like a wedding things move fast and setting your flash output manually is just not always a viable solution. With the Speedlites you can also manually control their output from your master if you choose not to use E-TTL. If E-TTL works well enough for you you don't need to buy radio triggers, which are an additional expense.
A quick (probably incomplete) device rundown
ST-E2: Canon's Wireless transmitter. Offers two flash groups, no manual output control (E-TTL only).
420EX: Discontinued. Very limited in a Canon Wireless configuration. Only supports E-TTL, no manual flash support whatsoever, no zoom control.
430EX: Great slave flash, full manual support for both flash output and zoom.
550EX: Discontinued. The ancient top model. Great as both master and slave. Full manual control like the 430EX.
580EX: Discontinued. The old model of the top of the line master and slave flash.
580EXII: The current top of the line Speedlite. Offers full manual control, and is the only Canon Speedlite with a builtin PC sync port. Dust- and water-resistance to match the 1DMkIII. On 40D and MkIII camera's (and perhaps the 450D) this flash can be fully controlled through the camera menu.
Note that all of the devices mentioned above also offer a focus assist beam for low light situations, but whether all of your focus points are covered by this beam depends on both the flash and the camera.
Lighting Groups
The Canon Wireless system uses groups A, B and C for the flash configuration (A and B only for the ST-E2). Groups A and B are used for lighting the foreground or subject, group C is for lighting the background. This is an important point to consider for your setup. If you set a flash to group C but you point it at your subject so your background isn't lit, E-TTL will boost up group C's output to maximum, desperately trying to light the background. Your subject will be overexposed. Put the flash in group A or B if it's pointed at the subject, put it in group C if it's not.
When you use E-TTL you work with ratio's for groups A and B. Using ratios means that you can vary group A and B output at half stop increments from 8:1 (A 8 times as bright as B) to 1:8 (B 8 times as bright as A). Group C is configured from -3 to +3 flash exposure compensation when using ratios. Note that your master flash (the 550EX/580EX) is always in group A.
If you do not use E-TTL but you go manual you can set each of group A, B and C in one stop increments from 1/1 to 1/128 flash output. For all of the flashes mentioned above you go manual by holding the Mode button pressed for a second or two, though you only need to do so on your master flash as long as the rest is set to slave mode. Note again that the 420EX will not work if you set your master to manual mode, it needs E-TTL to work at all. If you want to use a 420EX in your Canon Wireless system, E-TTL is your only option.
Getting your Master flash off-camera while preserving E-TTL
An on-camera flash doesn't provide for very flattering light. Ideally you'd want to have it off-camera instead, and there are two options to do so. You can use an E-TTL cord such as Canon's OC-E3 or a cheap clone, or you can use the ST-E2 as a master. Due to the limits of the ST-E2 (only groups A&B and no manual control) I've opted for the rather expensive Canon OC-E3 cable myself, but I've DIY modified it to extend it. Some pictures of this cable are further below.
Radio Triggers
I don't have any radio triggers myself, though I've read a lot about them. Basically, pretty much all the radio triggers (the new Radio Poppers are the exception) do not allow you to use E-TTL, which means that you will have to set the output of each flash manually if you want to use radio triggers. Canon Speedlites might not all work well in tandem with these triggers either, and if you use a 420EX you can only flash it at full output, if it works at all. Canon Speedlites were not really designed with radio triggers in mind, they're intended to be used with the Canon Wireless system. As the purpose of this article is the Canon Wireless system I'll stay outside of the realm of radio triggers - these are incompatible systems. I'll add however that I'm looking forward to getting the Radio Poppers when they become available in Europe and my budget allows it, as Radio Poppers relay the optical Canon Wireless signal (or the Nikon equivalent) through a radio signal, so the need for line of sight is no longer a problem with those and you get a larger range.
The Pilot button
When you've set up your flashes as master and slaves you can push the Pilot button on the master to see if the slaves see the optical signal from the master. If you're using E-TTL then first group A will fire, then group B, then group C. If you use manual output settings they'll all flash at the same time when you press the Pilot button. The slaves will also wake up if they went into power saving mode when you press the Pilot button.
Modeling Light
When you press the Depth of Field preview button on the camera with your Canon Wireless setup, the Speedlites will do a 1 second strobe burst. This might help you to position your lights. Be careful using this too often, after having used this feature 10 times quickly in a row you're expected to let your flashes cool off for 10 minutes (this is stated in your Speedlite manual).
A practical example (using E-TTL) with setup shots
First I'll show you what the picture looks like with just the 550EX on-camera. Very unflattering light for my subject (lets call him Jeremy), and a nasty shadow behind Jeremy. On human subjects it would look a lot worse though.
 
Here I've added a 430EX about 45 degrees left of Jeremy. This time I have turned off the flash of the master flash, and I've just set the 430EX to group B (the A:B ratio doesn't matter here, as only the 430EX lights the subject). So the 550EX just tells the 430EX to fire without contributing to the scene itself, and E-TTL takes care of the proper flash output. Note that I'm not using light modifiers such as a shoot through umbrella here which would provide softer shadows, it wouldn't add anything useful to this Canon Wireless tutorial and my shoot through umbrella is just too darn big, it would get in the way of the setup shots. If I had used an umbrella the shadow that's so obviously visible behind Jeremy would have been more pleasing or even non-existant though. And also note that if I would have moved the key light in really close to Jeremy the falloff of the light would have caused the background to go black as the distance from subject to the background would then have been a lot larger than the light to subject distance.
 
Aside from the shadow being rather harsh, it's too dark to my liking. This time I've re-enabled the flash of the 550EX, and I've set A:B to a ratio of 1:4. Remember that the master is always in group A, and I had my 430EX in group B ... so the 430EX that is acting as key light contributes 4 times more light to the scene than the master. The master is now acting as a fill light to brighten up the dark shadows.
 
Maybe we do not like the gray background, lets make it white. I've added my 420EX (yes, it's deliberately in view) in group C and I've set group C to +1 2/3 flash exposure compensation. I did not change the grey background cloth to a white one, but the flash makes it appear as such. I also took my 550EX off-camera instead with my OC-E3 cord, and I've put a white styrofoam reflector to Jeremy's left. So we now have 2 flashes here, a 550EX off-camera master, and a 420EX at +1 2/3 stops. The reflector provides some of the fill that the master gave before when it was on-camera. I've provided 2 setup shots here, to show you that my E-TTL off-shoe cable is modified to provide a length of about 2 yards instead of the standard 2 feet ... a modification that I can heartily recommend. Note that getting the background a proper white is the only shot in this example where I had to chimp a shot, E-TTL just took care of the rest for me and they were simply all shot in sequence as I made these changes.
 
For the purposes of this example, I've now put my 430EX on a light stand behind Jeremy and gridded+snooted it to act as a hairlight (I've made no effort to gobo the flash or hide it from the frame so the camera picks up some flare). Jeremy doesn't have the great hair that your own supermodel would have, but you can see the effect of the backlighting anyway. I've taken out the 420EX, so there are two flashes here, 550EX camera left as master, and the 430EX on the opposite side of Jeremy. They were set to a 8:1 ratio for A:B (550EX in A, 430EX in B). If the hairlight is too bright a few ND gels could further power down the flash, but Jeremy is not that great a test subject for establishing the proper flash output.
 
Lighting wise the most annoying aspect of the last shot above is the shadow. If I had used my umbrella this would not have been an issue, but there's another workable solution. I've brought back my 420EX to the scene, and this time I've set it to +1 flash exposure compensation. This makes the background much brighter than in the last shot but also eliminates most of that shadow.
 
Websites for more information on the EOS Flash System
photonotes.org/articles/eos-flash/
super.nova.org/DPR/Canon/
Finally
I hope you've enjoyed my little starting guide. Comments, additions and corrections are welcome.
Lianna
Posted at 9:17AM, 18 May 2008 PDT
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