Green Screen Use

Green Screen Techniques

I tought I saw a putty cat!

     In a previous post I touched on the use of green screen as a tool for video production and in this post I will elaborate on that and also include some tips for adding a green screen image to  your videos.  First of all lets consider how you can get green screen images and videos for your use.  The simplest way is to acquire images that are offered for free like this one of a Bengal Tiger that I copied from Google Images.  The same goes for Green Screen videos, a simple search for green screen videos will yield quite a few sites where you can download a variety of pre-made green screen subject matters.  Some care should be taken though if you intend to use these products in a commercial venture since there could be copyright issues.   The exception to this is the “Fair Use” condition which simply states that if you are offering your work for educational purposes (like this blog) you may use public photos in your work.  The best way to avoid problems like this of course is to produce your own original work when you are going to use it commercially, as a matter of fact Google will suspend your partners account for copyright violation.

Not that's a gun!

     So how do you produce green screen products of your own?  Well, if you are talking for photo use, it can be quite simple.  For example let’s take that green screen photo of the Tiger and add it to an existing photo like our Civil War cannon.  I am using Corel Draw and Corel Photo Paint software to make my green screen effect on my photos, but there are many other products that would do just as good a job.  First I opened Corel Draw and selected a new page, then I imported our green screen tiger image and our cannon image onto the page.  I then selected the green screen tiger and chose the edit bitmap command which automatically opens the Photopaint application.  I then used a color mask which lets you select a particular color range which in this case we want to be green so we can remove it, leaving you the remaining color ranges.  I then used a simple cut command to remove the tiger and went back into Corel Draw and selected the paste command, and magically my tiger with no green screen background appeared on the page.  After this it was a simple matter to do some resizing and adding of a shadow to create the new image of the cannon and the tiger, which is something you just don’t see everyday.

Maybe he was a mascot?

     Video is a bit more challenging but it is without a doubt the media form that makes the most use of green screen effects.  From movies to weather reports, to commercials, to Youtube uploads, the green screen adds action that enhances any video.  The phrase green screen by the way is just a generic term for what is technically called, “Chroma Key Compositing” or “Chroma Key” and the color used for chroma keying doesn’t actually have to be green.  For instance I produce a DVD for one of the National Civil War Battlefield Parks and I use National Park Service Ranges as narrators.  I have to video them in front a blue screen instead of green due to the fact that they wear green trousers and if I used green for the Chroma Key color their legs would disappear!

Green Screen and frame

Starter light set

     The major difference between chroma keying a video rather than a photo is that to do a photo you can work on a much smaller scale, in fact you may not even have to employ anything other than your computer and some image enhancing software.  Doing Video on the other hand can get more expensive.  First you have to have an area to hang the chromakey screen which sounds easy but remember the screen must go nearly from floor to ceiling, and if you intend to show your actors feet it must run along the floor also.  Proper lighting is crucial or you will have shadows and bright spots that will be difficult to deal with when you go to key them.  Lights and screens can run into quite a tidy sum so my suggestion is to start small.  You can go to most large hobby stores and purchase a piece of 32X40 foam backer board from the framing department and then go to the fabric department and buy a piece of fabric in the color appropriate for your project and cover the board with it.  Next experiment with small items, maybe even use puppet techniques to test you skills.
     Hopefully you will have success employing Chroma Key Composition because it can open up a world of possibilities for you in your video and photographic production.