Grass Valley Forums

Grass Valley Forums (http://forum.grassvalley.com/forum/index.php)
-   Editing with EDIUS (http://forum.grassvalley.com/forum/forumdisplay.php?f=7)
-   -   Blue screen or Green Screen in Edius?? (http://forum.grassvalley.com/forum/showthread.php?t=11088)

skybrady 04-15-2009 06:32 AM

Blue screen or Green Screen in Edius??
 
Hey guys - can you blue or green screen in edius?

if so how?

is it just a matter of filming somebody speaking with a blue plain (or green??) background and then using an edius feature to get rid of it and put another video behind?

any thoughts would be greatly appreciated!!

Shakeel 04-15-2009 07:29 AM

Do you mean replacing Green or Blue background with video ?
It can be done using Keyers > Chromakey

Standard Play 04-15-2009 07:30 AM

I actually just shot a music video in green screen today.

There are many Do's and Dont's. Ill try to organize this as best as i can.

Dont's
1) dont move the camera at all!! Camera must be on a tripod locked down.
This means no pans, no zooms, no camera motion at all. If the camera is moved, your subject will float around on the screen. No handheld shots!

2) dont have the subject you are shooting have anything too shiny that might reflect the green bc it will become invisible

3) dont have the subject wear anything green.


Do's
1) Pick your background out before you shoot!!! If you want a wide full body shot, you must know you can find a correctly proportioned bg. Also, If you want a tight shot, just shoulders and head, you have to get a high resolution bg that is in proportion. You cannot simply zoom in on the background in post bc it will look fuzzy.(thats if you want it to look like the same bg) If you are shooting a bg separately, make sure you zoom from the same distance away and at the same speed or it will not match up.

2) Sometimes marking the greenscreen with + marks will help you proportion the video right. Set + marks in slightly brighter color green to see, but not too far off that they wont key out. Space these about 1-2ft apart. green tape works well.

3) Use a lot of light. Screen must be lit bright and even. If not, there will be parts you may not be able to key out. Also light the subject accordingly. The studio i shot at today was called a cyclorama. the easiest way to describe it is like a skateboarding half-pipe ramp(not as much as a slope) that is pained green. This smooth slope eliminates creases and edges. Creases and edges are usually dark...key them...blah.

4) keep the subject a few feet from the screen bc you dont want to create shadow on the screen. once again, a shadow will be tough to key out.

5) Most of the time a bed sheet, or some cloth material is better than paper. Paper seems to reflect light more and can create highlights. Highlights...going back to the key issue.

6) many materials can be used. Cardboard, sheets, paper, oak tag, paint. if you are painting, you might want to get 2 shades of green depending on your lighting conditions. If you are hanging lights from high up, the top of the green screen will be brighter green than the bottom bc it is lit more. if you paint the bottom of the bg a lighter shade of green, it will help compensate for the distant lighting.

7) blue and green are used bc they are the furthest color from human skin.
if you chose a color too similar to skin, you will key out the edges around the person.

How to key out a color in edius.
effects palette-> scroll all the way down to keyers(Grey color)->chromakey.
drag it onto the mixer part of the video clip on the timeline. this clip should be on track 2. Track 1(or all tracks under your chromakeyed clip) will appear in the background

http://ediustraining.grassvalley.com/index.php
select number 6 "Effects" on left side on this site. 6.1 is chromakey.

You will not be able to add more than one keyer to a clip. If you wanted a 3d PIP and greenscreen keyed out you would have to do this....->
1) key out green on clip. dont add the background in yet!
2) open a new sequence
3) in the bin window, sequences are automatically saved as clips. select sequence one clip from the bin, and drop it in sequence 2. Now this clip is a formatted chromakey clip and the bg should be transparent. you may have to hit f7(layout) and change the settings on your fill color. this is near the bottom left. for some odd reason, when i put my fill color to black and set it to 10%, the bg is transparent. if i set it to 0% or 100% it is still there O.o... you can add a keyer, such as 3d PIP on this clip now.
4) add your bg to an underlying clip and you should be set!

also check out these vids.
http://www.youtube.com/watch?v=w6brdwY-dvU
http://www.youtube.com/watch?v=Eya3gBuA01U
if you watch the second video at around 1:50 you will see what i mean about zooming on a subject and watching them fly around the screen. if the bg doesn't change with it....


Ummm.. I think thats it lol
Sorry I wrote so much, but there is a lot that goes into this kind of a production and any little thing done wrong can kill the video.


GOODLUCK!!! :D

redgum 04-15-2009 09:40 AM

Really great advice, just clarifying number (4), keep the subject as far away from the background as possible and always light the subject and background seperately.
Green is more common for chromakey as it appears less often in human features (eyes). Everything else can be changed. Also, the DV signal is composed 2:1 toward green and in theory can key green better. And finally, the old blue screen of film days was less troublesome in that film could handle a broader range of chroma than the digital signal.

Gordon B 04-15-2009 06:31 PM

For what it's worth, I have just done some Chromakey in hi-def, it definately seems to key way better than SD.

Also to add to Standard Plays excellent post, if you are refering to something in the BG, make sure that you know where to (say) point, and make sure that the lighting of the key shot and the BG are pretty much the same.

Finally, if you are doing a piece to camera and your BG is an outdoor shot, don't make the sound too "studio", try to make it sound outdoor.

And finally, finally, try to get some movement in your BG shot, ie people walking past, traffic etc etc with sound which you can mix into your dialogue.

HTH,

Gordon.

Jerry 04-15-2009 07:43 PM

Quote:

Originally Posted by skybrady (Post 73516)
Hey guys - can you blue or green screen in edius?

if so how?

is it just a matter of filming somebody speaking with a blue plain (or green??) background and then using an edius feature to get rid of it and put another video behind?

any thoughts would be greatly appreciated!!

I think you would better served to use the green screen.
The blue channel is a "little dirtier" than the green channel.
Also, if you can capture directly to your hard drive to 4:2:2
Uncompressed format, hd preferred, your key will be cleaner and easier to
Accomplish.

STORMDAVE 04-16-2009 01:11 PM

I learned a while ago (through trial and error of course) that as much as you light your object, make sure to light the green screen also with a diffused light to keep it even. You don't really want shadows either since you might have some issues pulling keys in EDIUS. Other than that, green screen is highly recommended as Jerry mentioned in the DV and HDV (Also XDCAM) world and also the DVCPROHD and AVCINTRA world. If you're working at 4:4:4 (I don't think any of us are, since EDIUS doesn't support it) then you can use blue as well.

vortigern 04-16-2009 01:18 PM

I have found that blue seems to work better. In order to to big blue screen backgrounds I use plastic tarpaulins from DIY stores costing about 10 . They work well with EDIUS they would not pass for a feature movie but for the clients I have they are good enough. Never undrstood why green did not work well but that's how I found it.

redgum 04-16-2009 02:34 PM

Actually StormDave although DV and HDV (4:2:0 or 4:1:1 depending on where you are) work well with green I find any format (XDCAM) working in the 4:2:2 colorspace is somewhat different. The 4:2:2 colorspace contains equal parts of green and blue where it's two to one in DV/HDV.
Vortigern, chromakeying is a "creative" art that needs some technical nouse. Even the best DoP's still use trial and error to get the right look.

STORMDAVE 04-16-2009 08:27 PM

XDCAM EX is 4:2:0 (just like HDV)...XDCAM HD (the new 422 version) is 4:2:2.

4=Green
2=Blue
2=Red

So in these compressed formats, the green channel has the most information. Red and Blue get tossed out by half or more.


All times are GMT +1. The time now is 03:06 PM.


Copyright 2014 Belden Inc. All rights reserved.