How can eliminate monitor flicker from digital video?

February 14, 2005 12:29 PM

What is the easiest way to eliminate computer monitor flicker (from the refresh rate) that shows up in digital video? I'm taping some people for a company documentary and need to shoot them at their computers.
posted by strangeleftydoublethink to computers & internet (12 comments total)

1) set them up with LCDs.

2) you could try setting the refresh rate at 60hz, which should match up with the shutter, but you could get a stationary black bar.
posted by delmoi at 12:39 PM on February 14, 2005

Btw, I have actualy recorded video from an LCD and it was perfict. No flicker, no nothing.
posted by delmoi at 12:39 PM on February 14, 2005

You need to link the vertical refresh of the monitor and the camera together.

There's a name for this that I can't recall. genlink or something like that.

Here's a little guide with more info.

Here is some more help.

Basically, unless you are replacing the monitors with LCDs (which don't refresh in the same manner), you're going to be boned. :-(

Your one other choice is to feed a video feed to the monitor that is synchronized to the camera using a TV -> VGA box. This will sitll probably suck, but it's better than nothing.
posted by shepd at 12:46 PM on February 14, 2005

You need to adjust the shutter speed to match the refresh rate of the monitors, or vice versa. Your best best is 60Hz on the screens and a 1/60 shutter rate on the cameras.
posted by pmbuko at 12:46 PM on February 14, 2005

delmoi beat me to it LCDs don't refresh so they don't flicker.
posted by Mitheral at 12:48 PM on February 14, 2005

Another way to go is to set the displays to 75Hz and use an even slower shutter speed like 1/25. If you need to film the screens up close, this will cause some motion blur. If you don't really care about what's happening on the screens or their contents will be static, then do it this way.
posted by pmbuko at 12:48 PM on February 14, 2005

LCDs do refresh, but the pixels have an associated warmup and cooldown period, which prevents noticeable flickering.
posted by knave at 2:39 PM on February 14, 2005

What kind of camera are you shooting with? It is often less intrusive to synchronize the camera with the screens than the other way around. If you gave us a brand and model, somebody might be able to find out if it can be done.
posted by MrZero at 3:08 PM on February 14, 2005

It's a Canon ZR-65, so not many options on the camera side.
posted by strangeleftydoublethink at 4:06 PM on February 14, 2005

For your googling convenience, the word shepd is looking for is genlock.
posted by tss at 9:03 PM on February 14, 2005

pmbuko nailed it. I'm not familiar with the ZR-65, but most prosumer and up cameras (and a surprising number of consumer models) will let you change the shutter speed of the camera. Go through the menus or the manual -- you may very well have that option.

If you do have this option, it never hurts to show up at the location a little early so you can tinker with your shutter speeds with the actual monitors you'll be shooting...that way you can avoid the static black bar of which delmoi spoke.

Yes, shepd was looking for "genlock", but that's not quite the same thing. Genlock is typically when you have a master timing generator and synchronize everything to it...you won't be doing that in this situation.
posted by Vidiot at 10:13 PM on February 14, 2005

Get old monitors, rip the guts out, replace the screens with screenshots printed on clean white paper and put incandescent desklamps inside.

Make sure nobody moves their mouse or types anything.
posted by flabdablet at 6:32 AM on February 15, 2005