Shooting a computer monitor

[SilentBob102]

Quick question from a relative newbie --

I need to have a computer monitor in a shot I composed for a music video, and I know there is a fairly simple way to avoid the "flicker" effect you get when shooting a monitor as well as those annoying lines traveling up the screen. I remember it having something to do with refresh rates.

Can someone tell me the best way to avoid all that stuff when shooting in 60i HD mode?

Thanks

[tcindie]

The best way is to composite the picture onto the screen in post. ;)

[Fletch78]

As far as I know, with modern TFT and LCD monitors, flickering is not an issue anymore as they work on 60 Hz fixed (I even shot them with a PAL 50i cam and got no flickering). However, the problem is that you'll get an annoying moirée pattern. The only way to get rid of it is to find out the right distance/zoom combination between the HV20 and the monitor. If you get it right, the tft pixels of the monitor will 'melt' together on your footage and there won't be any moirée patterns.

But after all, I'd agree with tcindie. If you're a bit familiar with compositing and tracking, it's the best solution to add the picture in post.

[Erik Bien]

Older Canons (like my GL-2) have a shooting mode called "clear scan" for this specific scenario: it basically lets you bump the shutter speed up or down until the rolling black bar goes away.

I'm pretty sure all it's doing is matching the shutter speed to the refresh rate of the monitor, so, if you're shooting 60i at 1/60th, make sure the computer's display adapter is set at a 60hz refresh rate and it should work.

[SilentBob102]

Thanks, I'll have to do some experimenting. I'd rather not have to worry about it in post.

[2Bdecided]

I think it looks obviously faked when it's added later. It's a shame the HV20 doesn't have "clear scan", but it's fairly easy to get good results filming from a CRT if you can force its frame rate to match the HV20 (60 for "NTSC", 50 for "PAL") and choose shutter speed appropriately.

Unfortunately, you usually can't make PC CRTs do 50Hz, and most don't do 100Hz either - so in Europe, without clear scan, use an LCD in shot instead!

Cheers,
David.

[Fletch78]

I think it looks obviously faked when it's added later.

I agree, most often it does look very fake, but I'm sure it can be made less obvious. I hate obvious digital effects, so I always try to match them as good as possible. Good tools are blur and grain/noise (preferably matching the rest of the shot).

If an effect or compositing is clearly obvious, it's most often because of wrong perspective and unmatching picture quality (=the effect is too clean).

[tcindie]

I think it looks obviously faked when it's added later.

So, every cell phone commercial you've seen where you can see something on the display looks fake?

Like this example (http://imagineersystems.com/demos/movies/lab_601MidRes.php)
Or this one (http://imagineersystems.com/demos/movies/monet_PPO_MobileMidRes.php)?
Or if you want to get really crazy with it... (http://imagineersystems.com/demos/movies/monet_PPO_YorkACMidRes.php)

These are all samples using Monet (http://imagineersystems.com/products/monet/), but it can be done with any tracking system in any compositing program.

(The iPhone ads use this technique too.)

[Michael Davis]

Cell phone commercials aren't made by "relative newbie"s.

[tcindie]

No, but the question was what is the best way to shoot a monitor.

The easiest method would be to shoot an LCD, but depending on your shutter speed, refresh could still be an issue (though MUCH less of a problem than CRT's).. But it's certainly not the best method, and my point was that a composited image doesn't need to look fake, and with a little bit of effort it's really not very hard to do.

[Goose]

for shooting CRT monitors you can use powerstrip to tweak the refresh rate to 50hz or 60hz etc

[w.pasman]

For a CRT it is best is to use a whole multiple of the screen refresh rate. So if you shoot a 50Hz monitor, use 1/50, 1/25 etc. The higher the refresh rate of the monitor and the slower your camera shutter the better.

Worst is to have the shutter of your camera faster than the monitor. In that case you may see only half of the monitor.
Also bad is to be close to but not exactly the monitor speed. For instance shooting a 60Hz monitor with 1/50 will give you a twice as bright band somewhere in the picture.

With LCD panels the shutter speed also matters. This is because back lights, just as most fluorescent lighting, are flickering. Best use a relatively slow shutter like 1/20.

Most issues can readily be seen on your cameras display

[lordtangent]

Flicker isn't the only problem. I'm surprised nobody has mentioned the issue of exposure here also. Considering that the monitor is pretty fixed in brightness, you need to design all the rest of the lighting in your scene around it. (Otherwise it will either look too bright or too dim in the final image)

A huge mis-match in exposure is going to look just as "fake" as a bad composite.

[cheezerman]

The absolute best way to shoot computer monitors:

http://www.youtube.com/watch?v=HZ9AcvDAqAU


:hv20-smilie70:

[tcindie]

The absolute best way to shoot computer monitors:

http://www.youtube.com/watch?v=HZ9AcvDAqAU


:hv20-smilie70:


While not nearly as funny as some of the comments were intended to be, I can relate I guess.. I've had a few monitors that I could have liked to do this to.

[Michael Davis]

With LCD panels the shutter speed also matters. This is because back lights, just as most fluorescent lighting, are flickering. Best use a relatively slow shutter like 1/20.

Bleah. 1/20th is the strobiest "video" look you could hope for.

[w.pasman]

Bleah. 1/20th is the strobiest "video" look you could hope for.

What are you trying to say?

[Michael Davis]

That 1/20 looks like crap.

[2Bdecided]

So, every cell phone commercial you've seenI haven't seen a commercial for years.

However, the examples you provided were very convincing. I think £2,750.00 is a little beyond my budget!

Cheers,
David.

[2Bdecided]

for shooting CRT monitors you can use powerstrip to tweak the refresh rate to 50hz or 60hz etcYes, powerstrip works well with many CRTs (and video cards). 50Hz progressive on a PC monitor produces quite an annoying flicker in real life (might distract the actors!), but it can look OK through a camcorder.

Cheers,
David.

[tcindie]

I think £2,750.00 is a little beyond my budget!


I'm sure it is, but...


it can be done with any tracking system in any compositing program.

I used those examples, because they were the most readily available. :)

[smp]

one of the easiest ways is to print out a copy of your desktop then tape it to your screen. Depending on how visible the computer screen is in your shot, this works. If the computer screen is the main subject of the video I would use a screen capture ap. If a subject is using the computer in the shot, then you will have to do a clear scan. If you are able to I would use an lcd monitor and not a CRT, then you don't have to worry.

[w.pasman]

That 1/20 looks like crap.

Sorry but as a general statement this is just BS.

[tcindie]

If you are able to I would use an lcd monitor and not a CRT, then you don't have to worry.

That still depends on your shutter speed.. It is possible to see the refresh at certain shutter speed settings, but for the most part you are right, LCD screens are much easier to capture on video than are CRT displays.

[Michael Davis]

Sorry but as a general statement this is just BS.If there is anything moving in the frame whatsoever, it is solely my personal opinion that anything less than 1/24 at 24p or 1/60 at 60i looks stupid. (And I don't love 24p at 1/24, but I can stand it.)

[tcindie]

I agree, but shooting 24p with a 1/24th or slower shutter is kind of pointless as it kind of defeats the purpose -- in that it won't look filmic since that would mean the shutter would be open for the full length of every frame, and that's physically not possible with a film camera.

Well, you COULD do it by removing the shutter from a film camera, but you wouldn't end up with any kind of usable picture. ;)

[w.pasman]

You can go to 1/6 in shutter prio mode.
As long as you have more or less static images on the display even 1/12 looks good to me.

[mrob7]

just put a blue screen image full screen on your monitor, then chroma key it in post and add whatever you'd like

[tcindie]

just put a blue screen image full screen on your monitor, then chroma key it in post and add whatever you'd like

Doing a corner pin without trying to chroma key it actually works better, as you can use the existing luminance on the screen for realistic reflection mapping. ;)

[Michael Davis]

You can go to 1/6 in shutter prio mode.The human ass can survive getting a bowling pin stuck in it, but I wouldn't recommend doing something just because it's possible.

[Michael Davis]

...he said, with his tongue, firmly in cheek.