transparency problem using chroma key

lucseawalker wrote on 11/1/2011, 4:51 PM

I filmed somebody in front of a green cloth and I want to replace the green cloth by a photo.

I put the photo on track 1 and the video sequence on track 2.

I use chromo key effect on the video to have the green cloth disappear and itv works.

The problem is that I still see the photo superimpose on my video! The video is not clear, looks like both the photo and video are mixed together ...

What should I do?

 

I am using Magix Movie Edit Pro 17 Plus version 10.0.11.0 on a WindowXP Pro SP3

Comments

yvon-robert wrote on 11/1/2011, 5:17 PM

Hi,

Rule 1 When you use a green screen the subject (Talent) must be about 6 feet in front of the green screen.

Rule 2 The green screen is lith unifomely using 2 lights at 15 degrees, one placed at left and the other placed at right.

Rule 3 The talent is lith using 3 lights, one the main light strong on subject at 45 degrees, the second light  call the fill light about 50% intensity or less of the main light  at 45 degrees on the opposite side. And the third light to light the talent at the back on the shoulder this light is just enough to separate the talent from the green screen and avoid a green outline on the head and the shoulder just enough power.

Rule 4 Run the camera in manual mode manual focus and focus on the talent.

Regards,

YR

 

johnebaker wrote on 11/1/2011, 5:43 PM

Hi

Just to add to YR' post - the colour of the green cloth must be a very bright green - almost lime green to get the best result.  

The 'mixing' effect you are getting is almost certainly caused by variation of the green colour of the background green cloth due to not being smooth enough or lit correctly - see below.

To expand on the lighting - the subject (talent) should be the source for the manual exposure setting of the camera take this reading with the subject lit but the background unlit and manually focus on the subject as well. Then turn on the light(s) for the background, ideally you want to slightly over expose the background so any variation in light intensity is flattened out.  

Note you can also use a dead black, bright blue or white cloth with chroma key - it all depends what colours are in the subjects clothing. For example a blonde haired subject wearing very light clothes would probably be better against a black background

HTH

John

Last changed by johnebaker on 11/1/2011, 5:43 PM, changed a total of 1 times.

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yvon-robert wrote on 11/1/2011, 9:20 PM

Hi John I can add extra hints:

Color of the green screen is Pantone DS 284-3C or corresponding to CMYK 60-0-70-20 normally when I use a picture I use pure green as green color.

2) If talent is 6 feet from green screen the camera in front of talent must be normally 6 feet when possible.

3) Side walls left and right must be dark to avoig reflection on talent. (Black drape)

4) For lights I suggest to use the new spiral neon 5500K, all light must be the same color. (Daylight neon)

Uniform lighting of green screen is a must, visual inspection or you shot a picture and use the pipet (eye dropper) to check variation using a paint program.

Regards,

YR