I'm pretty new to flash photography and have never used studio strobes. I have been researching for weeks and trying to figure out what studio flash system I want to invest in. At the moment I'm considering getting the Elinchrom 500 BXRI set. My plan is to later also get a single style RX1200 head to use as my main light when I need to overpower the sun etc and use the 500s as fill lights. Here's my issue:

- As I understand, the flash duration on the 500 BXRIs is different to that of the RX 1200
- I'm also under the impression that flash duration changes according to the power setting on the flash (with full power being shortest duration)

- Now if I want to shoot a studio portrait of an action shot with these three lights all at different power outputs...will the 500s (used as fill light) still cause motion blur even though my main light's flash duration is quick? Basically as I understand it, I will be bottlenecked to the slowest flash duration of the 3 heads when using them together. Is this correct?

Help would be really appreciated!