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Keying out LCD monitor displays

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Andy Hill
Keying out LCD monitor displays
on Sep 13, 2011 at 7:44:35 am


I'm a bit stuck on the best way to get the results I want out of after effects.

I've got a tracking shot of my office and want an element (meteor/fireball/anything really) to travel through the computer screens then eventually set alight a vase on the table.

It was shot on a Sony Excam, lit with a blue light and the movement was on a rail.

Before we filmed it I changed all the computers to a green screen saver to make it easier to key out. There are 6 monitors in total that end up in shot.

Here's where I hit some snags, keylight 1.2 doesn't pick up all the correct levels of green as they are lcd and change during the track. There is also a lot of spill from the screen savers on the desk, I've tried duplication and precomp to separate each screen on a separate layer as well as the standard keylight keying but can't seem to get rid of the spill or get a descent result from keylight.

Any ideas would be greatly appreciated :)


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Tudor "Ted" Jelescu
Re: Keying out LCD monitor displays
on Sep 13, 2011 at 11:56:15 am

This seems an easy job for Mocha - planar tracking/corner pin. Check out this tutorial for tips:

Tudor "Ted" Jelescu
Senior VFX Artist

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Michael Szalapski
Re: Keying out LCD monitor displays
on Sep 13, 2011 at 2:08:05 pm

To get rid of the spill, try the technique in this tutorial: [link]
Basically, you apply hue/saturation (to an adjustment layer, in your case) and change the colors it's going to affect to green. Tweak as needed. Then roughly mask it off, if needed.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.

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Darby Edelen
Re: Keying out LCD monitor displays
on Sep 13, 2011 at 6:58:51 pm

Ahhh, the perfect post for me to rant on the evils of green screens again. Let me clarify. Green/Blue/Colored screens are useful in a lot of cases. One of my biggest pet peeves, though, is the assumption that a Green or Blue screen is the best solution without considering the specific context of the shot.

In your case the best solution would likely have been to simply leave the monitors turned off. This has numerous benefits, among them:

1) No color cast by the monitors (you can 'add' a color cast from your replacement footage in AE).
2) Maintains environmental reflections and ambient lighting in the monitors.
3) No keying required.

You could use mocha to track the screens or if you have the foundry's camera tracker you could do it that way. Once you have your track and your new footage locked to the displays it can be integrated on the display easily using the Screen blend mode.

Black screen with subtle ambient light and reflections + footage set to 'Screen' mode + a little bit of color correction as necessary and I promise you the footage will look like it's on the display. Keeping the ambient lighting and reflections is a huge bonus for this workflow.

I implore anyone reading to consider their options before first assuming Green/Blue screen is the way to go.

Darby Edelen

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