Can't quite Key properly in FCP6. at DVinfo.net

James Collins · May 24th, 2009, 02:54 PM

I have taken some video of me against a green screen and have managed to key out most of it, apart from a section in between my legs, which was caused by a shadow.

Any suggestions for getting rid of this? Is it possible to save the video, re-import the 'almost keyed' version and then key it again for the new shade of green?

Bill Davis · May 24th, 2009, 04:15 PM

James,

What you're facing is the reality that the quality of any key effect is a function of not one thing, but at least 5 or more things.

Camera - Recording Format - Lighting - Shot Content and finally, the Software used to try to pull the key. (we'll ignore minor oddities like wardrobe pattern and color, subject eye color, etc, etc.)

Camera quality effects the ability to pull a clean key. Roughly speaking the better the camera electronics, lens and recording electronics, the cleaner the original shot and the better chance you have of a clean key.

Recording format is important if you're keying from recorded shots. Uncompressed HD will key better than highly compressed formats like DV, or HDV - and the more color sampling information you preserve - (search 4:2:2 color sampling verses 4:1:1 for example) can have a large effect on clean keying.

And, of course, lighting is CRITICAL. Not just smooth key surface lighting, but proper separation from subject to key screen through light spill control so that there's not a lot of key color spill reflected back onto the subject.

And speaking of the subject. Shot content, like whether the subject has whispy red hair or a shiny bald spot also greatly affect clean key outlines.

Finally, the more sophisticated the software being used to key the final composite, the more tools you'll have like multiple mattes to block out areas of poor lighting, secondary color keying, and shadow preservation.

Sorry, but keying is somewhat complex. Hardly ever as simple as shoot, push a button, and get a perfect Hollywood style key.

It's way easier than ever with modern digital video production tools to pull an OK key. But just as hard as it's ever been to pull a really professional one.

Hope that helps.

May 24th, 2009, 02:54 PM	#1
James Collins Regular Crew Join Date: May 2009 Location: UK Posts: 59	Can't quite Key properly in FCP6. I have taken some video of me against a green screen and have managed to key out most of it, apart from a section in between my legs, which was caused by a shadow. Any suggestions for getting rid of this? Is it possible to save the video, re-import the 'almost keyed' version and then key it again for the new shade of green?

May 24th, 2009, 04:15 PM	#2
Bill Davis Trustee Join Date: Jan 2004 Location: Scottsdale, AZ 85260 Posts: 1,538	James, What you're facing is the reality that the quality of any key effect is a function of not one thing, but at least 5 or more things. Camera - Recording Format - Lighting - Shot Content and finally, the Software used to try to pull the key. (we'll ignore minor oddities like wardrobe pattern and color, subject eye color, etc, etc.) Camera quality effects the ability to pull a clean key. Roughly speaking the better the camera electronics, lens and recording electronics, the cleaner the original shot and the better chance you have of a clean key. Recording format is important if you're keying from recorded shots. Uncompressed HD will key better than highly compressed formats like DV, or HDV - and the more color sampling information you preserve - (search 4:2:2 color sampling verses 4:1:1 for example) can have a large effect on clean keying. And, of course, lighting is CRITICAL. Not just smooth key surface lighting, but proper separation from subject to key screen through light spill control so that there's not a lot of key color spill reflected back onto the subject. And speaking of the subject. Shot content, like whether the subject has whispy red hair or a shiny bald spot also greatly affect clean key outlines. Finally, the more sophisticated the software being used to key the final composite, the more tools you'll have like multiple mattes to block out areas of poor lighting, secondary color keying, and shadow preservation. Sorry, but keying is somewhat complex. Hardly ever as simple as shoot, push a button, and get a perfect Hollywood style key. It's way easier than ever with modern digital video production tools to pull an OK key. But just as hard as it's ever been to pull a really professional one. Hope that helps.