The Portable Photo Studio
(A FAQ on Canon Wireless Flash Photography)
There is a lot of interest these days in Canon’s wireless flash solutions, and there also seems to be a lot of dis-information floating around out there. I am going to offer up the details on the setup that I am very happy with, and the results of my real world use of these products in conjunction with Canon’s DIGITAL camera bodies. Due to the length of this document, The Portable Studio equipment list is on a separate page HERE. In this article, the term Dxx refers to any of: EOS D30, EOS D60 and the new EOS 10D.
Questions, and comments are welcome, all flames are automatically routed to /dev/null!
For your convenience, here is an index of the questions, just click on the question to go to the page with the answer. If you are new to Wireless Flash, you may want to just read through page by page, since I have tried to keep the questions ordered in such as way as to provide an informative document with a logical sequence.
Q1: What do I need to get started?
Q2: I’m new to this wireless flash stuff. What is a slave, and what is a master?
Q3: I’m confused about Channels, and Groups (also called Slave IDs). Explain.
Q4: What is a Ratio, and how does it relate to a Group?
Q5: What are the differences between the ST-E2, and a 550EX used in Master Mode?
Q7: Can I assign more than one Wireless Slave the same Slave ID, and why would I do this?
Q8: Can I use the ST-E2 with just one slave, and why would I do this?
Q9: Does Flash Exposure Compensation work with the ST-E2?
Q10: Which Wireless Slave do you prefer, the 550EX, or the 420EX? Why?
Q11: I’m getting very inconsistent flash exposure results in ETTL mode, what’s wrong?
Q12: I’m using a EOS 1D(s), and things look a little dark, what’s wrong?
Q13: Do you use your Wireless setup in ETTL mode, or Manual mode? Why?
Q14: Which is better, Canon Wireless Flash solutions, or dedicated studio flash systems?
Q16: What camera settings do you typically use with your Wireless Flash setup?
Q17: Have you ever used a Wireless Flash setup with a Canon film body?
Q18: Does the ST-E2 work with any of the PowerShot Cameras?
Q1: What do I need to get started?
A1: You need at least one “master” controller device, and at least one “slave” device.
Wireless Master (Controller) Devices:
ST-E2 Wireless Transmitter
550EX Flash Unit
MR-14EX Flash Unit (Macro Ring Light)
MR-24EX Flash Unit (Macro Flash System)
Wireless Slave Devices:
550EX Flash Unit
420EX Flash Unit
Q2: I’m new to this wireless flash stuff. What is a slave, and what is a master?
A2: A wireless Master is any of the above mentioned Canon flash units. It is the device that the camera uses to transmit flash trigger information via pulses of light to the other flash heads, so that a group of Canon flash units will work as one. There is just ONE wireless master in any given flash setup, and it is the device attached to the camera hot shoe (or alternately, on a flash bracket, connected to the camera via a hot shoe extension cable). A wireless slave is a Canon flash that can read these pulses of light sent out by the master, and use them to fire the flash tube at just the right moment, with the correct level of light output, anywhere from 1:1 all the way down to 1:128. Currently there is just one Canon flash device that can be a Wireless Master, and a Wireless Slave, and this is the extremely versatile 550EX. While often overlooked, both of the new Canon Macro flash units can be used as wireless master devices. Some great, dramatic results can be obtained by adding one or more slaves to your macro flash setup.
Q3: I’m confused about Channels, and Groups (also called Slave IDs). Explain.
A3: Channels allow different wireless setups to be operated in the same area without interference between the individual setups. Every master can talk to the slaves on ONE of four unique channels. You need to make sure all of your equipment is on the same channel, otherwise it will not be operating as part of your wireless setup. Presumably Canon did this so that up to four photographers could work with up to four different Wireless systems in the same room without triggering each other’s equipment. On the other hand, Groups, or Slave IDs allow the master device on your camera to send up to three different instructions to three or more slave units. Each slave with the same Slave ID will operate as a Group (even if it is just a “group of one”), and will receive the same instructions from the master device as every other slave in the group, should there be more than one. This allows the use of Ratios, see the next question for further details.
Q4: What is a Ratio, and how does it relate to a group?
A4: To answer this question, we need to have a quick look at one of the most important aspects of studio photography (and movie cinematography as well), the concept of Key lights, and Fill lights. Few would argue that shadows are a very important part of the human visual experience, giving us clues as to size, shape, and distance. One of the keys to being an artful photographer is mastering light and shadow, and this is where Key and Fill lights play a big role. To create shadow, and simulate light patterns that our brain is familiar with, it is usually desirable to have one light brighter than the others, just as the Sun is the brightest light outdoors. But lighting a subject with just one light can create deep shadow, and often result in unappealing results. It is often desirable to set some additional lights at one or more strategic locations around a subject, but make them considerably dimmer than the main light. These are called Fill lights. Canon uses the term Ratio to describe the ability of a Wireless Master device to set two (ST-E2) or three (550EX) different brightness levels amongst the Wireless Slave devices. A typical example might go something like this. You decide that you want to do a portrait of your 10 year old son inside an old building in your town. You want the lighting to be dramatic, since you have dressed him up in a period costume for this special occasion. You get him to strike a pose against a grainy old wooden support beam, and you arrange one 550EX flash on a stand about 30 degrees to your left, and the other about 40 degrees to your right. You then use the Ratio buttons on your ST-E2 to set the flash on the left to fire at full power (the Key light), and the flash on the right to fire at 1/8 power (the fill light). You select your focusing point, compose, and shoot. The resulting shot will give the impression of a moody yester year picture, with lots of shadow on the right side of his face, but the 550EX that fired at 1/8 the power on the right side ensures that there is still a reasonable amount of detail visible on the right side of his face and body.
Q5: What are the differences between the ST-E2, and a 550EX used in Master Mode?
A5: Probably the biggest difference between the ST-E2, and the 550EX used in Master mode is the number of groups controllable by each. The ST-E2, being based on older (circa 1998) technology, can control only two unique Groups, A, and B, whereas the newer 550EX, when used as a Wireless Master is able to control three unique Slave IDs: A, B, and C. There is also the difference of size, and weight: The ST-E2 is a tiny little box (smaller that the diminutive 220EX flash head), and adds virtually no weight to your camera body. If you do not need the feature of a third group for ratio control, you will likely prefer the profile of your camera with the ST-E2 attached. Also, I like the speed, and simplicity of the ST-E2 user interface.
Q6: I really like the idea of three groups, but I rarely / never use direct lighting of my subjects. Can I turn OFF the flash output completely of my on-camera 550EX operating as a Wireless Master?
A6: Yes! Check out page 104 of the 550EX User Guide to find out how, or just keep playing with the “Set/Sel” button until that menu pops up. You can then turn off the on-camera 550Ex’s light output altogether. Do NOT use the camera body custom function that adjusts flash firing and focus assist to “Emits/Does not fire”, since it is the 550EX’s main Xenon flash tube that emits the trigger pulses for the Slave Units, and this CF setting disables the main flash tube altogether. This custom function should only be selected if you are using the camera body in low light situations where auto focus is an issue, but you do not wish the flash to fire. It will work with all the Canon flash units right down to the diminutive 220EX, and even this small flash can provide a better AF assist beam than the on camera AF lights provided with the Dxx series bodies.
Q7: Can I assign more than one Wireless Slave the same Slave ID, and why would I do this?
A7: Yes, you can put several / many flash heads operating in Wireless Slave mode on the same Slave ID. In the simplest scenario, you do this because you do not need to set the ratio of light output between the different flash heads. Another popular reason is that you require more light output to light up a large group of people, or a large object. Let’s say you want to light a large object, and that you want to have most of the light coming from one side (referred to as a Key light), but you still need a bit of fill lighting on the other side. You discover that one 550EX firing at full power in the Key light position does not provide sufficient light for your needs. Add a second 550EX Wireless slave on the same Slave ID as your first Key light, and place it very close to the existing key light. All Wireless Slave units assigned the same Slave ID will fire at the same output, so you now have two 550EX units acting as one Key light. Another reason to use two or more Wireless Slaves per Group is to reduce flash recycle time. I have often been in the situation where shooting in a particular location, a single 550EX per light stand is firing at, or very near full power. This results in at least a 4 second recycle time, lengthening as the batteries wear down. And while four seconds does not seem like much, you can easily loose a great pose or expression. When working with “regular” people (as opposed to professional models), their best expression or pose often happens after the flash fires, and those eternal four seconds can mean the difference between a shot that the client likes, versus one that the client does not. The same applies to working with animals… they seldom co-operate with your photographic desires, and Murphy’s Law ensures that the perfect moment passes while your flash recycles. The solution is to put more than one Wireless Slave on each light stand (or location if you are not using light stands). Two 550EXs firing at half power recycle so quickly that they can actually keep up with a 3-5 frame burst from a Dxx, or 1Ds camera (Or a 1D is low speed continuous mode).
Q8: Can I use the ST-E2 with just one slave, and why would I do this?
A8: Yes. I like doing this for outdoor daylight fill flash, because it gives an extremely natural catch light in the eyes. My preferred settings are to disable “Auto Reduction of Fill Flash” via the custom functions on the camera body, and to manually set flash underexposure on the camera body between 2/3 to 1-2/3 stops of under exposure. I would normally do this in conjunction with Aperture Priority (Av) mode to give a nice, natural exposure balance to the background. If the ambient light is fairly bright, you will typically need to activate the high speed sync option on the ST-E2 as well (H lightning bolt). If ambient lighting is low, you may need a tripod or monopod, because the camera will set the shutter speed quite low to balance the exposure of the subject with the background. Then place the slave flash head anywhere from 10 to 45 degrees angle from the position you wish to stand in to photograph the subject. Trees, fences, and passers by make handy light stands if your photo session occurs on the spur of the moment.
Q9: Does Flash Exposure Compensation work with the ST-E2? The User Guide says camera based flash exposure compensation does not work, but you just told me to do this in the question above.
A9: The User Guide lies! I am happy to report that Flash Exposure Compensation works very nicely with the ST-E2 when used with any of the Dxx or 1xx series DIGITAL bodies. You can prove this to yourself by setting any of the above mentioned bodies to Tv or Av mode, and dialing in some exposure comp on the camera, and taking a picture with your slave flash unit(s) operational. I can only assume that the information in the ST-E2 user guide (which does not appear to have been updated since it’s original printing in 1998) refers to the EOS 3, and possibly other film bodies of that era.
Q10: Which Wireless Slave do you prefer, the 550EX, or the 420EX? Why?
A10: The 550EX is an incredibly powerful, and versatile flash unit, andcarries a hefty price tag to go with it. If I was just going to use one flash attached to my camera, I would go with the 420EX for it’s lighter weight, smaller size, and lower cost. But since I almost exclusively use multiple flash units, I find that I need the versatility of the 550EX. While the 420EX is a great little unit, with a lot of light output, it lacks most of the advanced configuration features of the 550EX when used in a Wireless setup. One of the most crippling features that the 420EX lacks in a Wireless setup (for me) is Manual mode. I invariably find the 420EX cramping my style when I am forced to use one as part of a multi light setup.
Q11: I’m getting very inconsistent flash exposure results in ETTL mode, what’s wrong?
A11: This question has little or nothing to do with Wireless Flash photography, and is way outside the scope of this document. Basically, it has to do with the way the Canon ETTL flash metering system works, and some common misunderstanding that most aspiring hobbyists, and even some professionals have about the system. 95% of all ETTL exposure problems can be traced back to the camera user having recomposed the scene (moving the camera) after pressing the shutter button half way, and allowing the camera to meter the scene. The short answer solution to this problem is: NEVER, NEVER recompose a scene after allowing the camera to meter it. Use your camera body custom functions to link metering to the active focus point, and move the active focusing point to reflect the part of the scene you want in focus. Since the Dxx bodies to date only have three focus points, and they are not often where you need them to be, you must learn to use the Flash Exposure Lock function on the camera body. The EOS 1xx series cameras with their plethora of focus points are much more likely to have a focus point where you need it – use it! Another option when shooting Wireless is to use Manual mode, see the next question.
See these great ETTL Flash FAQs if you really want to master Canon ETTL flash.
Q12: I’m using a EOS 1D(s), and things look a little dark, what’s wrong?
A12: This is a very good question, and the jury is still out on this one. It would seem that the EOS 1D, and the 1Ds both underexpose the flash by 2/3 to 1 stop. Some say this is to prevent blown out highlights, since it is easier to recover an underexposed picture than an overexposed one. I have never seen an official statement from Canon on this, and I can easily and consistently reproduce this situation on both the 1D and 1Ds that I have access to. The flash underexposure is only obvious when the flash is the only source of light, and only manifests itself when the flash unit(s) are in ETTL mode. My solution is to dial in about 1 stop of flash exposure comp, which takes care of the problem. Interestingly, the amount of flash underexposure on the 1D(s) produces near perfect results when the camera is set to Av mode, and the flash is being used as fill (as I discuss in Q8,Q13 and Q16), which might lead one to wonder if perhaps Canon engineers set the camera up to give perfectly natural fill flash, and then expect the user to adjust the camera accordingly when the flash is the only source of light. In a twisted kind of way, this makes perfect sense, since these bodies are targeted at professional photographers who would typically use studio flash systems when flash is the only source of light. Since studio lights require full manual adjustment of the camera (as discussed in Q13 and Q16), the default flash underexposure leaves the camera perfectly configured for the only occasion that a pro would typically use on camera or wireless ETTL flash – daylight fill flash. Regardless, it would be nice if Canon would document this somewhere!
Q13: Do you use your Wireless setup in ETTL mode, or Manual mode? Why?
A13: I usually use Manual mode. I seldom find that the focusing points are where I need them to be, and therefore need to use Flash Exposure Lock (FEL). Experience has shown that most regular people, and even many professional models will drop their pose after they think the flash has fired, and unfortunately FEL fires a test flash that most people mistaken as the real flash. Even with my subjects warned of the test flash, I find that it cramps my shooting style. It also doubles the number of flashes fired, and discharges the batteries faster, which can be a problem when shooting for long periods of time. I find that I can work much faster by setting each 550EX to the power ratio I want, and then moving the light stands or subjects as required during a shoot. The big exception to this rule is when I use one or more 550EXs as fill flash outside. Since I often ask a passer by, or someone’s child to be a “living light stand”, the test shots, and moving of the light(s) required to set up a manual mode shot are too tedious, and I use ETTL mode in conjunction with FEL. Also, trees, fences, and walls (other spur of the moment light stands) don’t tend to be too co-operative when it comes to changing positions either.
Q14: Which is better, Canon Wireless Flash solutions, or dedicated studio flash systems?
A14: The answer to this question depends on a lot of things. Let me start by saying that I MUCH PREFER using studio flash systems. There is simply no substitute for the pure power, and virtually instantaneous recycle times of a good set of studio strobes. Not to mention the vast array of really cool light modifiers that can be used with studio strobes… scan through a bunch of fashion mags, and look closely at the models’ eyes… you will quickly see what I mean. Also, there is the issue of cost. You can actually get a very nice studio strobe with a lot more light output, complete with a basic set of light modifiers for the same or less money than a 550EX. In my opinion, one of the best values in studio lighting comes from a manufacturer with the unlikely name of “Alien Bees”. Having said that, there are MANY occasions where dragging around a bunch of studio strobes is completely out of the question. This is where the beauty of the Canon Wireless solution really shines. With just a medium sized suitcase, and a camera backpack, you can travel almost anywhere in the world, set up, and be taking studio quality shots in a matter of minutes (well, OK, the traveling part might take a bit longer).
Q15: Can I use the St-E2 to trigger a studio flash unit and avoid having to attach a wire to my camera’s PC socket?
A15: Yes, but with a little modification. The basic problem is that while the near IR output of the ST-E2 is quite sufficient to trigger the optical sensors on most studio flash heads, the studio flash systems mistake the initial transmission of control data that the ST-E2 sends out to the Slaves as the signal to fire. So when the camera body sends the “fire all Slaves” command out via the ST-E2, and releases the shutter, the studio slaves have already fired but not yet recycled enough to fire again. The result is an underexposed or black frame. The solution lies in something as simple as a small piece of paper. By inserting a piece of paper in the hotshoe as you slide the ST-E2 in place, you can cover the four side contacts, while leaving the center contact exposed. This has the effect of turning whatever is mounted on the hotshoe into a non-ETTL device. Indeed, it is the center contact that would be used to fire the studio strobes if your camera lacked a PC socket, and a hotshoe to PC adaptor was used. Similarly, it is the center contact that is used to fire any type of third party “dumb” flash unit, such as the famous Vivitar 283. Fortunately for us, the signal to “fire all Slaves” is transmitted to the ST-E2 via the center contact, and is in fact just a simple flash, disguised by the red filter on the front of the ST-E2. It may require a bit of fiddling to get the paper in just the right place, but once inserted, you will be rewarded with a really handy little optical trigger for virtually any studio flash system that supports optical slaving. Note that this also disables the AF assist lamp, so you will need to insure that there is sufficient light in the studio to allow for un-aided focusing.
Q16: What camera settings do you typically use with your Wireless Flash setup?
A16: While this isn’t strictly a Wireless Flash topic, when I see comments like “What’s wrong with my camera, I’ve got it set to Av, and the shutter speed is really slow, even with the flash on”, or “ Such and such isn’t working, I’ve got the camera set to P mode…” I feel that it is worth discussing how you SHOULD be configuring your camera, if you are the lucky owner of any or all of the equipment mentioned in this FAQ. Let’s start by de-bunking this one: “What’s wrong with my camera, I’ve got it set to Av, and the shutter speed is really slow, even with the flash on”. This very correct and desirable camera behavior is documented on at least one page of every EOS camera manual as far back as I have access to, which is 1993. Aperture Priority (Av) mode is designed to balance the background exposure (ambient light) with the foreground exposure (flash). So if it is night time, and the background is quite dark, your shutter speed will naturally be quite slow since the camera is trying to properly expose darkness! Av mode is my personal favorite for outdoor fill flash work, as discussed in Q8. I leave the flash(es) in ETTL mode, dial in some flash underexposure, and the result is a photo with a naturally lit subject, and a nicely balanced background. If you do it right, the fact that a flash was used should hardly be noticeable. Most other times when I am working with flash, either on the hot shoe, or Wireless, I have the camera in full manual mode (M). Is that a few “that’s too difficult”s and “but I bought this camera with all this automatic stuff”s I hear out there? Face it, you are the only one who really knows what you are trying to achieve. In most cases where the flash is the only source of light, such as the studio, you probably want your shutter speed to be the X-sync speed, since shutter speed is irrelevant in the exposure, it’s only purpose being to stop or allow blur if there is motion (click here if you are having trouble with this concept). That being the case, I usually set the shutter speed between 180 and 250 (depending on which body I am using) to prevent blur if possible, and then choose an aperture that will be pleasing to the subject matter, and the composition. For the type of work I do, this typically falls in the range of f4.0 to f8.0. So we have determined the shutter speed, and the aperture, now what? Your final decision is whether to set the flash to ETTL mode, or to go totally manual. In ETTL mode (given that you use it properly), the camera will take care of everything else, all you have to do is take the picture. If the flash(es) are set to manual mode, then you will need to take a few test shots to get the levels right. When evaluating the test shots, use the “info” display, and look at the histogram to evaluate your exposure, since the on-board LCD screen tends to show the image considerably brighter than it actually is, depending on camera model, and user configurable LCD brightness settings. It is also useful to remember that you can adjust the ISO setting to compensate for larger or smaller rooms and subjects without having to change aperture, although for quality reasons, I normally stick with ISO 100 or 200. Common pitfalls to avoid: Shutter Priority (Tv) mode in conjunction with flash will always use the largest aperture of your lens. If you are using lenses with big apertures, you are going to end up with really short depth of field, and on some off brand lenses, really soft pictures. Program mode (P) – I think Canon engineers put this mode on the camera just in case you absolutely have to allow someone who knows nothing about cameras to take a picture of you and your loved ones in some tourist spot. It is a general shooting mode that is good for just about nothing except possibly a family snapshot taken by a passer by. It will usually pick shutter and aperture values completely unsuitable for commercial grade photography. If you have a Dxx body with PIC modes (mountain, face, flower, runner, etc), you should forget they exist altogether. This is evidenced by the fact that no EOS 1 professional series camera has ever had these modes at all. Learn how, when and why to use M, Tv and Av modes, and you will find your shots looking better and better.
Q17: Have you ever used a Wireless Master Slave setup with a Canon film body?
A17: No. I am sure that after posting this FAQ, I will be told in no uncertain terms that it works great with the EOS xxx film body. In fact, I am sure I could borrow a friend’s film body, and shoot some great sessions on it. But as I mentioned in a question above, my preference of Manual mode under certain circumstances would make using film bodies very inconvenient for me.
Q18: Does the ST-E2 work with any of the PowerShot Cameras?
A18: You wouldn’t think so from the literature, but I was surprised to discover that the ST-E2 does work on the PowerShot G2 (haven’t had a G3 to try yet), albeit with some fairly serious caveats. First off, Canon really crippled the G2 hot shoe, and off-board flash capabilities. This is a shame, since for the price, they could have easily ported some of the technology from the low end Rebel film cameras over to their highest end point and shoot. My three biggest complaints are: First, the G2 can not use the off-board flash / ST-E2 focus assist light, leaving you stuck with the worthless onboard focus assist system. Second, the G2 can not use (as in does not fire) an off-board flash when the camera is set to full manual (M) mode, which makes life very difficult when you wish to control both aperture, and shutter speed. And third, the G2 can not use an off-board flash in high speed continuous mode, Duhhh, hello, there is NOTHING high speed, or continuous about the on-board flash (This is not really a ST-E2 issue, more an off-board flash complaint in general). Having said that, if you can live with the settings that P mode dreams up, or you can fight out an acceptable Av or Tv setting that pleases you, and works from a technical perspective, AND you can get enough light on the subject to get a decent focus lock, voila, you can use the ST-E2 to fire one or more Wireless Slaves!
That just about wraps up the Canon Wireless Flash FAQ for now, so let’s go have a look at The Portable Studio.
If you are having trouble with the concept of shutter speed not affecting exposure when the only light source is the flash, consider this: The typical duration of a Xenon flash tube discharge is typically 1/5000 to 1/64000 of a second. If this is the case, does changing the shutter speed from 1/60 of a second to 1/200 of a second make any difference to the exposure? No, it does not. If your flash is set to ETTL mode, the camera will quench (or shut down) the flash when it has received enough light. In manual mode, or with studio strobes, it is up to you to measure what constitutes sufficient light, and adjust by moving the light source, or adjusting the output of the light source. You could also compensate by adjusting the ISO speed, and or the aperture. Regardless, when flash is your only source of light, the only setting relevant to the proper exposure of the film, or sensor chip is the aperture, never the shutter speed.