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Sebastian Gross
02-28-2014, 08:28 AM
hey there,

i had a shooting recently where i had to adjust my bmcc 2.5k EF to a smartphone screen of which i didn't know the exact screen frequency (because it was a prototype).

i live in PAL land and my assumption was that the refresh rate of the screen would be somewhere close to 60Hz, simply compared to other models.
so if 50Hz equals a 180 shutter, 60Hz should equal a 216 shutter in PAL land.

but no shutter value seemed to balance out the "hum" running down the screen. and yes i made sure that i exited the menu after each value change.

the only thing that did the job was switching to an unconventional 29.97fps with an 180 shutter, which not only left me with questions but also with quick decision making like switching to a 100% controlled environment with 100% flicker free lamps so i wouldn't run into any obstacles.

job worked fine but i'd like to unravel this (even with the unknown variable X which is the actual screen refresh rate of that smartphone).

any suggestions / experience on that?

much obliged.

sebastian.

jtfarabee
03-03-2014, 12:45 PM
Was there a lot of motion in the scene? If I am shooting a static shot of another screen, I usually set the shutter angle very wide (sometimes 360) to make sure it doesn't flicker. Even if the screen refreshed at 60hz, you would need to be either perfectly in sync with the refresh, or film at a slower shutter speed to make sure that you are capturing a full refresh cycle.