Flicker free HMI meaning?

You will not see any flickering at standard frame rates of 24 and 30 but when you shoot high speed or change you shutter angle you will pick up flicker.
 
I've worked on both the Arri 1200w HMIs and (unfortunately) those chinese 1200w HMIs. There is not flicker on the chinese ones

Kinda offtpic: From what I could tell the color temperature and everything seems the same, the Arri looked like it threw a bit more light, but one thing you WILL notice from the chinese hmi is immense wear/tear, since Arri has done the science in airflow, and china just copies/pasta, that puppy will break down fast. And be careful with their electronic ballasts, I recall we've had one of them refuse to strike one time. And another 575 fixture that decided its brand new bulb wasn't hip enough to live its full life.

Good luck
 
Let's clarify on flicker at 24/30, because that's only related to film cameras. Film cameras have flicker-free filming speeds, but CMOS video cameras do not. You could get banding or flicker at any frame rate, if you use the wrong shutter speed. Or you could get flicker-free performance at any frame rate, if you use the right shutter speed. When using an HMI (especially a magnetic-ballast HMI) with an MOS-based video sensor, there are "safe shutter speeds", not "safe frame rates". And those safe shutter speeds are dependent on your power line frequency. If in 60Hz territory (like the USA) then the safe shutter speeds are divisors of 120, so 1/120, 2/120, 3/120, 4/120, and 5/120 are safe shutter speeds (or, put another/better way, 1/120, 1/60, 1/40, 1/30, or 1/24). If you're in PAL/50Hz territory, then the safe shutter speeds are 1/100, 2/100, and 4/100 (1/100, 1/50, and 1/25).
 
Barry_Green said:
...Film cameras have flicker-free filming speeds, but CMOS video cameras do not...
Click to expand...

Film cameras' flicker potential is just as dependent on shutter speed/angle as digital cameras. Only archaic or supercheap film cameras have fixed shutter angles. 144 degrees is a standard setting on adjustable shutters for just this reason.
 
You must log in or register to reply here.
Back
Top