Greenscreen advice...

[Ismail Aslam]

Hi,

I was working on a current project where i wanted to shoot a bunch of face on interviews with a greenscreen and then morph the interviewees like the sequence at the end of the micheal jackson music video 'Black or White'.

I dont currently have a greenscreen and was in the process of purchasing on and was wondering if anyone could give me any advice on what sort of material i should purchase, any recomended stores/ebay and what sort of light i might need?

Also if anyone knows of any interesting tutorials online, please let me know?

Any advice would be appreciated

Regards
Ismail

[Don Donatello]

i've been using the 5x7 fold up flexdrop 2 ( green/blue) by photoflex for past year ... works very good ...

[Ismail Aslam]

What about lighting?

[Don Donatello]

have never lit the flexdrop ..
on current project i'm using natural light ..
so the green screen is not evenly lit = no problem on the uneven lighting ..
keying software either ultra 2 , keylight (in AE) , or combustion 4 keyer ..
basically i get a good key around persons head/shoulder and garbage matte the rest of the frame ...

had some problems with a few persons hair - the messy hair look with lots of ends sticking up/down/out - problem has been when shooting 4:1:1 color space hand size camera = lot of noise in those ends of hairs .. do not have same with 2/3 CCD size camera's ...

[David Tamés]

Originally Posted by Don Donatello

lot of noise in those ends of hairs .. do not have same with 2/3 CCD size camera's ...

It's not really an issue of 1/3" chip vs. 2/3" chip, but an issue related to the way color is ecoded, 4:2:2 color (as found on most 2/3" chip cameras) vs. 4:1:1 color, used in most 1/3" cameras. The severe undersampling of the color is the source of the problem, to split hairs, so to speak. I'm sure this has been covered in detail in other threads.

[Don Donatello]

take sony 2100 and sony 500 series 2/3 chip camera .. shoot green with both and you will find the 500 series is much easier to get a clean matte ..both record to 4:1:1 ... or for that matter take any hand size SD camera ( except dvx100) and put it up against any 2/3 " CCD camera (dvcam) and the larger ccd files is much easier to work with ... IMO the larger CCD just has cleaner electronic's while the smaller CCD have to add much more electronic edge enhancement/sharpening ...
the dvx100 is the exception ..

add 4:2:2 color space and that makes keying even better/easier ...
would be interesting to compare keying HVX 200 dvcpro 50 vs. the panasonic 900 dvcpro 50

[David Tamés]

Originally Posted by Ismail Aslam

What about lighting?

There are some excellent tutorials and discussions on the net regarding green/blue screen work, so I will not go into too many details (see the list of links at the end of this post) but as far as the lighting itself goes, here are some tricks-of-the-trade:

1. light the green screen as evenly as you can, but there is no need to go overboard, as today's chroma-keyers are pretty good at dealing with slight uneveness in the background,

2. have the subject positioned as far from the green screen as possible to avoid the effect of green spill on them,

3. use backlights with a little bit of minus green (magenta) gel on them, usually 1/8 and rarely any more than 1/4, to neutralize any green that might be falling on the subject in order to make it easier to pull the matte,

4. light the subject in a manner consistent with the background, in other words, the key light should be coming from the same angle and have the same quality as it has in the background plate,

5. don't overexpose the green screen,

6. by all means, you'll learn a lot through experimentation, have your editing workstation on the set if you can, do some tests...

There are many more details, but those are the major ones to watch out for, here some tutorials on the subject for futher reading:

Down and Dirty Green Screen by Walter Graff (excellent) http://www.film-and-video.com/broadc...eenscreen.html

Chroma Key Basics for DV Guerrillas (Part 1) by Charles Roberts http://www.videouniversity.com/chroma1.htm

Chroma Key Basics for DV Guerrillas (Part 2) by Charles Roberts http://www.videouniversity.com/chroma2.htm

And there are quite a few green screen discussion to be found by doing searches here on DVi...