Sadly, I have yet to find the "perfect" solution for off camera flash using speed lights. I've been through RadioPoppers (an early adopter), thru PocketWizard TT5 (also an early adopter) and am now using the Canon 600EX RT and transmitter. Each of these have had their annoyances.
First a question:
Can the 600EX RT focus assist beam be turned up?
It has been awhile (not since the days of using RadioPoppers) since I last put a 580EX II on camera and used the AF assist to help me shoot weddings and other events. I don't remember ever feeling aggravated that I couldn't focus in the dark, the AF assist always seemed to work flawlessly for me.
Last weekend I shot an event (not terribly dark, lots of disco lights flashing, nothing unusual, really) using the Canon 5D Mark III with the 600EX RT on camera and I had a terrible time focusing. It was embarrassing. Not just the dancing (where everyone is moving - which has never really been challenging before), but even some of the portraits I did (meaning people holding still / posing for the camera) with the lighting going on in the background were VERY hard to focus.
I've been through Canon 1DIII, 5D, 5DII and 5DIII with Canon 580EX, 580EXII and now the 600EX and this is the first time I've really felt like I was having a hard time focusing at an event.
A side question, WHY didn't the transmitter come with a focus assist beam? I bought two transmitters because I generally run two cameras simultaneously with several speedlights positioned around the room. But I have to give up at least one of my speedlights when shooting events in order to get AF assist.
When I was using the PocketWizard TT5, it also didn't have AF assist. But what it did have as a hotshoe. So I put a video light in the hot shoe and used the video light to help me focus during events. I didn't really like lighting people up with a video light - but at least it didn't cost me another speedlight to get focus assist.
However, the RT transmitter not only doesn't have AF assist, but it also doesn't have a hotshoe. So I'm left wondering where to attach my video light and ended up having to use a speedlight instead. I verified that the focus assist beam was working (I could see it lighting up people's faces), but it was very dim compared to what I remembered of my old 580, 580EX and 580EXII assist beams.
So there's my question... can I turn up the power of the beam?
And ultimately... can we get a transmitter that has built in AF assist?
The thing that I absolutely LOVE about the TT5 is the AC-3 Zone Controller. With 3 physical sliders and 3 physical dials, I can very quickly, in the dark, set any light off or on - ettl or manual and at whatever power level I wanted (ettl or manual).
With the RT transmitter, you have to wade thru CONTEXT SENSITIVE MENUS - one wrong push of a button and it takes you several more pushes just to get back to where you need to be. And then turning a light on or off requires getting into the right part of the menu, scrolling up or down to get to the correct group, pushing another button to toggle on or off or another button to select the power level and more buttons to turn the power levels up or down. The entire process is TEDIUS and ERROR PRONE which creates huge delays (as compared to the TT5 which, with the flick of a switch changed to the exact setting I wanted and I could do it with my eyes closed).
So my request, for the future, is ... can we get a transmitter that has real buttons and sliders to control the power levels? The LCD is uber cool ... but tedius.
Now I'm not claiming theTT5 is perfect. I would not have switched to the 600 if I thought it was. But my point at the beginning is valid. I have yet to find the "perfect" off camera flash control system.
Well I read your post a few times. I picked up a Canon 5D3 about 6 weeks ago and a 600 last week. Last evening I did a bunch of shooting in dark rooms and the combo seemed to perform well. Seemed pretty bright to me. I have not been in the field with disco lights yet so I can't comment. I will have to go to a non-important event for further testing.
I can see losing AF focus assist being a pain especially for you with 2 cameras. Gets expensive to tie up two 600 units so you can have focus assist. If I set up additional flashes I normally have a flash on my camera and bounce if I can. I typically only have two extra flashes going at this point but it sounds like you have more. I shoot with two cameras as well. Not sure where I will go with this. I just may just keep my 580 for my crop and 70-200 combo, go solo and use the 600 and other flashes for the 5D3, 24-70 and additional flash combos. Wider coverage. Of course if I'm doing portraits the flash is off camera and there is always enough ambient light. Here is where I will enjoy this unit. Being able to adjust all the flashes from the ST-E3-RT. Hopefully Canon will respond with focus assist.
My gripe was how to fire the flashes remotely with my Sekonic L-358. I use a PCB trigger attached with Velcro to the L-358 and receivers at the flash/es. I asked for some suggestions on other sites and a simple solution came up. Walk around with the transmitter and use the test fire button. Two things in hand but I can always hang the L-358 around my neck. I'm hoping Sekonic or someone comes up with a Canon transmitter module. Currently it only works with PW.
I posted a question on this forum - my first. I wanted to know if I connect a receiver in the remote release terminal of the ST-E3-ER and fire it from the transmitter attached to my L-358. I don't have a ST-E3-RT yet - I'm about to order it. Since I am trying to get away from third party RT I don't need an answer to that. I'll just use the test button until something better comes up like a Canon transmitter module for a sekonic light meter.
Now there are three improvements required.
I was at a wedding last night and using the 600EX-RT on ETTL with my 5D3 and the 24-70mm f/2.8 II. I was shooting 'blind' when all the lights were turned-off but for the disco flashing LED lights. Admittedly, there is a lag of approx. 1 to 1.5 sec for the flash to 'pop' but each time it was focused and properly exposed. I was actually amazed and loving the result. Turning-up the focus assist beam my very well shorten the lag but otherwise, right now I am happy with it.