With my canon equipment, I set one speedlight to master, and the other speedlight to slave (via the wireless system). I set the Elinchroms to ignite when the Canon flashes go off, via their built-in slave unit. I do it this way because out-of-the-box, the Elinchroms can be triggered by the light output of the speedlites, not vice versa.
I set all flashes to manual flash only. This way I can control the light best.
- first create your setup
- Then just set the Speedlights to M and dial in a fraction of full power, i.e. 1/32 or 1/8
- Set the Elinchroms to any sensible number to complement your exposure
- fire some shots and check which flashes need adjustment
- tweak until happy
- Do your shoot.
You would typically first use your Elinchroms and you would only need to use your speedlites when you need more light sources, such as a hairlight or extra strobes to blow out the background.
This is what I would do.
You could also use a radio transmitter with receivers, one for each flash. Or use the Elinchrom Skyport system, you'd have to buy a universal receiver for each flash (about $100 each). That would set you back $200, where you can have it all with basic functionality. I do need to say that radio transmitters are more reliable.
As for manual or E-TTL: You could use ETTL for your SB900's, but the Elinchroms won't flash automatically and need to be set to manual anyway. You can get tricky effects, because the SB900 output can vary depending on the light absorbing/reflective behaviour of your subject. If it's a live subject, it will change pose and your exposure may vary along with it, because the camera aims at getting average exposures. Having different flash output for each consecutive shot is not something you want, because you will spend more time in post. But you could just give it a try and see what happens. You can always switch to manual any time you like. You will find that manual is easier, you just need to do it once and you'll be sold on it.
If you, like me, like to shoot occasionally a portrait at f2.8 or wider, go for the RX300 !
Need more power ? Increasing your ISO is an option.
Often the problem is "too much light" and not as much "not enough" in such a "small" studio.
I'd suggest going for the 300RX instead of BXRi 500/250. BXRi does not support computer remote function which I think is a great tool for studio. In Asia, there is another FX Master Ri 600 kit for around USD 1k. It contains 2 flashes (with std reflector) + 1 remote trigger. This FX Master series supports computer remote feature.
