I recently purchased the Elinchrom Ranger RX with an A Head and tried to test it out on a location shoot. I know that freezing action depends on the flash duration of the strobe which is 1/1450th at max power. So keeping that in mind I placed the strobe about 8 ft away from the model and used Rembrandt lighting at a 45/45, turned the power to half which would compute about 1/700th of a second (more than enough to freeze action).
I set my camera to AI Servo and had the model flare her dress to capture the flow of the fabric, but to my surprise most of my shots were out of focus and my AF point was directed at the models face at all times. Also, you could still see trails of blur from the fabric when it was in motion. Am i doing something wrong? What is the most effective technique to use when capturing motion while using strobes on location? I do appreciate your feedback