Lay to tape with alpha channel?

[Greg Leslie]

Ceri — HDCam doesn’t support an alpha.

Usually, graphic elements that need to be keyed are layed off in two passes: a matte pass and a fill. The matte is just the black/white-shades-of-gray alpha element, and the fill has been modified to correctly show transparent pixels when keyed.

You give the tape to someone, they re-digitize the matte and fill (or copy them to another tape deck), sync them up and use the former to key the latter.

hope this helps,

Greg Leslie
Tulsa

[Doug Beal]

In the old days we’d lay off the fill and the matte as two separate layoffs that could be later injested and keyed. Unless you have an HDCamSR 4444 will not be possible in one pass.

Doug Beal
Editor / Engineer
Rock Creative Images
Nashville TN

[Mark Suszko]

We cheat this by putting the elements over a chromakey green background when laid to tape. Then key it at the other end. You coudl also use white or superblack (zero IRE on your scope) and later do a change of blend mode, or a luma or even difference key, depending on how complex the element is.