Your 40D will work like a charm with the CyberSync system. The ST-E2 is most often used for controlling an off camera lighting setup consisting of Canon Speedlites with Canon ETTL in charge of exposure, and you in charge of ratios. Hold that thought for a minute.....
You didn't mention if your Canon strobes were first gen, or Mk II models. If they are first gen, you need to buy a cheap hotshoe-to-sync cord adapter for each, as only the recent models offer built in PC sockets. In any event, If you buy a CSRB unit for each Speedlite, and a CSR(B)+ unit for each PCB light, you can fire the entire mess from a camera mounted CST unit in perfect fashion.
The reason I suggested that you buy CSR(B)+ units for your PCB strobes is that it sets you up for the future purchase of a Cyber Commander unit, which you can keep in your pocket at the sidelines, or in the stands, and change the output of all of your PCB lights to suit changing conditions, or just to suit your whims. The non "+" CSR(B) units don't offer that level of communication, and you will end up having to upgrade when the CC bug bites you.
The non "+" units do work fine for triggering non PCB strobes like your Canon Speedlites though, and save you a few bucks by not having to pay for features that you don't need. So, a basic CyberSync system can trigger all brands of lighting that you have previously (manually) set the power settings on by pressing your 40D shutter button with the tiny CST unit mounted in it's hotshoe.
Add a Cyber Commander unit later, and you can also control the output of all of the recent vintage PCB lights in your setup (including Einstein) from your seat. That rocks, but it would still be nice to also control the output of your Canon strobes from your seat. Maybe you can...
Back to your ST-E2 for a moment. I never bought one, as I couldn't see spending that much cash, and not getting a light with it. Even if I only used a 550, or a 580 as an on camera master with it's strobe switched off, it was still another fully functioning strobe in my kit. The ST-E2 also limits the number of groups you can control, as (I think), it counts as one all by itself. I do think that other than those couple of issues though, it offers the same remote control functions as any modern Canon strobe capable of master duty (like your 580).
If that is the case, the ST-E2 should allow you the ability to remotely set the power output of any canon slave unit set to manual mode that it can "see" well enough to communicate with from camera position. So, you might be able to remotely trigger AND control the output of your manual mode Canon slave strobes from a hotshoe mounted ST-E2, while your CC controlled PCB flash units are triggered by the tiny CST unit plugged into the PC sync port on the side of your 40D. That would be awesome.....
I'm going to try the scenario out using a 580EX with it's flash tube switched off mounted on the camera hotshoe as a standin master unit for your ST-E2 control unit. I see no reason why it wouldn't work just fine beyond the understood fact that a Canon master unit communicates it's orders via light waves, and can't be heard if it can't be seen, along with the minor problem that those orders are sent in a short burst at sync time....
As I understand it, the opening of the 40D camera shutter simply causes a standard X-sync message to be sent to the hotshoe and side PC terminal of the camera that lets anything connected to either port know "I'm opening now, and in 1 millisecond (?), I'll be fully opened, and I'm very likely to begin closing in another 1/125 of a second from then. Do your thing.".
If that is the case, then the camera is not waiting around for the master flash unit to respond. It is just broadcasting a statement, and going about it's business. That means that the Canon master strobe (or ST-E2) on the hotshoe must complete all of it's chatter giving orders fast enough that all listening slave units can hear the master, and comply so fast that they can still deliver light up to a full pop before the fully open shutter begins to close at any speed from the top 1/125 sync speed of the camera on down.
Bear with me here. Although I have not tried your exact scenario yet, there have been many times that I have used a hotshoe mounted 580EXII that was configured in master mode to control a bunch of manual mode 580EXxx slaves positioned out of view to properly light a large furnished interior shot (usually enough reflective surfaces to allow slaves to hear the master in a room), while a Pocket Wizard unit was plugged into the PC port to trigger other lights that were set up to illuminate hallways, stairwells, and secondary areas visible through open doors that I did not want to record as dark areas in the scene.
I have done that with 30D, 40D, and 50D cameras without any funky sync problems between the two light systems cropping up, so I'm pretty certain that if Canon is giving it's wireless system extra time to set up for a shot over the time granted for standard x-sync event, that additional time is added to the front end by a signal from one of the peripheral pins on a Canon hotshoe, and doesn't affect the timing of the actual "fire the flash tube" signal that appears at the side PC port, or the center hotshoe pin.
There may still be a potential problem issue when mixing strobist type camera flash units, and studio flash units in scenes where freezing fast motion is required, and both flash systems share the major role in lighting main subject. In that case, it's possible that the communication delay between the Canon strobes (within the sync window), or just the difference in flash peak/duration times between the two types of lights can cause an out of register double image to be captured in the frame. That said, I think you could avoid that trouble by separating duties between the two types of lights, and giving one type a several stop edge over the other type as the primary light source at spots where fast action is likely to occur (like goal zones).
Anyway, there is some food for thought. CyberSync is a very reliable standard radio trigger system that works just fine with most any light on the market. It has built in signal ports to allow it to play in the same sandbox with other remote systems, and best of all, it can be optioned up at very reasonable expense to "shock and awe" levels of lighting control. The potential to work and play with other systems that offer basic remote output control is a sweet bonus.
Sorry for posting a book in response to a simple question, but you brought up an important subject in modern photography that so many people I meet "know about", in a general sense, but they never had an opportunity to connect the dots that draw a mental image of the "why and how" details about it to allow them to really be creative in how they can make it work for them (and others). Maybe the boring detail will spark you, or one of the other people out there who are far more clever and creative than I happen to be to come up with some new ideas, or maybe someone will just hit me with a bat (typewritten, I hope), and correct my understanding of where all those electrons are headed when we press the the go button on a camera....
Voyager
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