Art Adams and Adam Wilt teamed up recently to get the skinny on sync rates and flicker issues when shooting with HMI lighting fixtures. They very thoroughly explain the issues at hand, and offer best practice guidelines for shooting. They also make a good case for dispensing with that old-fashioned shutter degrees nonsense when shooting digital, in favor of fractions of a second. Here’s a snippet:

“An absolute shutter speed states exactly what the exposure time is: 1/48th, 1/60th, etc. A relative shutter speed is usually denoted in degrees, because that’s how film cameras work: at 24fps, a 180-degree shutter results in a 1/48th of a second exposure; but at 23.98p, a 180-degree shutter results in a 1/47.96 exposure, which is NOT an HMI safe speed.”

It’s a fantastic article, check it out.