Maximizing Chroma Key Extraction Efficiency In Special Cases

[Lin Evans]

A Technique for Maximizing Chroma Key Extraction With PicturesToExe

One of the issues with using Chroma Key Extraction with nearly any software not specifically designed for that purpose is that there is almost always a light green or blue “halo” which will surround the video subject shot against a green screen or blue screen backdrop. Even with powerful software designed to specifically extract subjects from green screen video, it is sometimes an issue.

Of course there are certain “rules” which must be followed when doing the initial video capture. There must be no wrinkles in the backdrop which tends to change the uniformity of the shading, add shadows and make extraction much more problematic. Then the subject of the extraction must be sufficiently far away from the backdrop so that the green or blue shade doesn’t cast unwanted color reflections and of course the backdrop must be properly lit to create uniformity of color making it much easier to extract.

With all of the above done properly, chroma extraction with PTE will still usually leave a slight green “halo” around the subject. After extraction, placing the subject on a backdrop of complementary color (such as green) will de-emphasize this issue, but in some cases, especially with amenable subjects, there is another way to proceed.

Below are some screen snaps to show one way of dealing with this issue in PTE with amenable subjects. I created the running horse for chroma key extraction using Particle Illusion, a software widely used by the movie industry for special effects.

Original – notice light green “halo” around the horse

Conversion to Sepia – changes color of horse to a nice chestnut hue

Conversion to grayscale – very close to original except no visible green halo!

So essentially, what has been done is that in PTE the chroma key extracted video has been converted to either sepia or grayscale. In the case of amenable subjects this effectively removes the green halo without resorting to use of green backdrops to “blend” the halo. Obviously, if the chroma key extraction is of a video subject not amenable to this, it will not help, but in many cases the subject may already be of a more or less monochrome shade and the color adjustment feature of PicturesToExe can be put to optimal use.

Lin