ChromaKey effect

Videocentricity

Contributor Location: Long Beach,CA Joined: May 21, 2007 05:37 Messages: 394 Offline

Solved by

Jun 08, 2007 12:48

I'm using a green screen backdrop lit as best I am able and then adding the recorded video as a PIP.

When I use the chroma-key eye dropper to pick the background color (green) I get the expected effect and I am able to use the intensity slider to adjust the transparency from zero to a point where even the wanted image is affected.

So far so good...

However due to minute variations in the lighting intensity of the backdrop I get speckles and other errors in the final output. The more imperfect the lighting setup, the worse the speckling, so I know its my lighting at fault, not the software.

My question is - Is there any way to obtain a broader value for the chroma-key (maybe by adjusting a value in the windows registry for the chroma-key function??)

In other words make chroma-key dissolve darker-green and green and lighter-green colors in the video data not just the single color tone chosen by the eye dropper..

I have scanned the internet and see other more expensive packages offer a band of color adjustable around the color picked.

FYI I am using six tungsten pearl floods to light the wall - all purchased in a single pack so I assume they have the same color temperature. My main subject lighting is a halogen flood.
If you can't solve the problem - Change the problem

Videocentricity

Contributor Location: Long Beach,CA Joined: May 21, 2007 05:37 Messages: 394 Offline

Jul 01, 2007 17:39

This is a reply to my own original post.

For anyone considering Green Screen work, here is my solution.

The prime problems are
1. even lighting of the green screen and
2. green halo affect on the subject - especially hairlines

While still not perfect I settled on using three fluorescent strip lights as shown here

http://www.fidmania.com/studio/

By adding a 500 Watt spotlight as a backlight to the subjects head, I think I have solved the halo effect. Since its a backlight, any actual overbrightness does not seem too important.

I chose to make the frontal lighting form a semi-circle with six 100 Watt pearl lamps and I am getting a nice shadow free overall illumination. The only thing I need to beware of is reflections on eyewear when shooting the subject full-on, which can be fixed by shooting off-center.

I made the frontal lighting gantry from wood rather than metal since I dont have a workshop or metalwork skills. Fibre-board and glue did just fine for my low budget. The green screen is a felt cloth like a pool table surface.

Hope this helps anyone who is contemplating green-screen work. If you can't solve the problem - Change the problem

Dafydd B

Senior Contributor Joined: Aug 26, 2006 08:20 Messages: 11973 Offline

Jul 02, 2007 05:08

Ron,

I have read your posting and the link you gave. I think you have provided members of this forum with some useful ideas and a solution, super posting mate...keep up the good work.

I'd like to see some of your green screen work too!

Thank you.

Dafydd

Leela J

Newbie Joined: Aug 17, 2009 13:14 Messages: 2 Offline

Aug 19, 2009 18:07

Hi,

Advice needed please, I'm a newby to PowerDirector and currently trialling PD8.

I'm enjoying mastering the program and playing with chroma key effects, which we will be using for professional teaching videos, with the teacher in front of a Powerpoint animation (made into a movie), and other fun things also incoporated as Pips.

After some trials we purchased a vivid turquoise bed sheet from Walmart and it's easy to key out.

I'm experiencing the same slight prob which ever backscreen we use - a fuzzy line of the original backscreen color around the moving (human) subject always remains.

I'm using a Canon FS200 on auto focus, and I usually increase the exposure a couple of stops to get the subject light enough.

The backscreen is lit by four 250w construction lamps.

The front subject is lit by two long-life lamps - 23w but equivalent to 75w each.

Is there too much difference between front and back lighting do you think?

or is my prob to do with focus,

or can I improve my 'keying-out' technique in PowerDirector?

Any tips and tricks would be appreciated.

All respect to Dafydd, I watched a number of the tutorials on You Tube, thanks!

LeelaJ Leela, co-founder of a personal development business, just starting to make teaching videos.