Back in September 2004, Laurence Grayson explored the chroma-keying effect and explained how easy this is to create, even with entry-level editing software. But setting up blue- and green-screen effects requires an appropriately coloured background, careful lighting and software with decent keying ability. Making it look realistic is hard.
Matching the foreground with the background is where the skill lies. You need to decide how the two will go together from the beginning - both need to be shot accordingly.
However, there's another way you can create transparency effects without all the hassle of shooting against a blue screen. The idea is that you shoot your subject as normal, but have extra footage of your background which doesn't contain the foreground subject.
By careful blending and subtraction, a number of eye-catching effects can be created. You can make your subjects look partially transparent, as though they're ghosts, or you can have them miraculously appear, to create a Star Trek transporter effect.
All you need for this is software that supports more than one video layer, such as Pinnacle Studio Plus 10.0, Ulead VideoStudio 8.0 or Adobe Premiere Elements. Any higher-end program will do too.
The key to the two main effects I'm describing here is to have a background that's as static as possible. A tripod is essential - avoid moving your camera during a shoot. If you have a remote control, it may be preferable to use this to prevent you jogging the frame. If you do accidentally knock the camcorder, even just slightly, you'll have to start again.
Avoid moving backgrounds. If you have grass or trees in the background and it's a windy day, the motion is likely to spoil the effect. You'll need to shoot all your footage quickly so the lighting is the same and it's best to avoid days where the clouds keep casting varying shadows. In essence you want the background to be exactly the same whether or not your subject matter is in it - otherwise it'll end up looking blurry. This will spoil the effect.
Ghosts in the machine
Creating a ghostly figure or object is dead simple, if you'll pardon the pun - see Figure 1. All you need is two shots - one with the action in it and another containing only the background.
Simply place the action shot in a layer on top of the background footage and change its transparency settings. The way to do this depends on the software. With Adobe Premiere Elements or Pro, for example, you can vary the transparency of a layer without having to add an effect. You can use either the rubber banding on the timeline to do this, (see Figure 2) or open up the Effect Controls-Properties in Premiere Elements 2.0 with the upper layer selected. You can even vary the transparency to have your ghost fade in and out.
Ulead VideoStudio 8.0 and above offers direct transparency control via the Motion and Filter tab in Overlay mode, although you can't vary the setting with time (keyframing). To achieve a similar effect with Pinnacle Studio, you'll need the Plus version for its extra layer. Place the action clip on the second video layer and add an image in Picture, using the Full Screen preset. Then use the Transparency slider to choose how see-through you want your subject to be against the background. With Studio Plus 9.0, you can't vary the transparency with time other than using a simple fade-in/fade-out effect. Studio Plus 10, on the other hand, gives you similar levels of control to Premiere Elements. You can also play with audience perception by working in black and white - or even shooting with your camera's infrared night mode - and adding motion blur to the ghost track if your editor supports it.
Our second effect is a little more involved than the first, because we're going to add a video static effect to represent the matter-transportation process. This requires four layers of video, so only Premiere Elements, Vegas MovieStudio or a professional video-editing package will suffice.
During the "beaming down" section, your subject will be motionless, so shoot them standing still for a second or so before they move about. Then extract the first frame - File-Export-Frame in Premiere Elements - to create a still image as your entry point.
Place your background footage on the fourth video track, then leave a space and place the action footage a little further along, starting at the point where your subject was standing still. Next, drag your exported still frame to the timeline just before the action begins and extend it so that it overlaps your background (see Figure 3).
You'll now have to load up your image-editor. Open your exported still frame and use a lasso tool to draw around the subject in the shot. Invert the selection - Select-Inverse in Photoshop Elements - and press the <Delete> button to remove the background. Revert back to your subject and fill it entirely with black.
Save the file in your image editor using a file format that supports transparency (preferably PSD), load it back into Premiere Elements and place it on the third video track. Ensure it is overlapping the entire original still on the timeline.
You'll now need something to stand in as the static. For this, you could use your camcorder to record a TV channel that shows white noise, or do what the original effect creator did and record a close up of a cheerleader's Mylar pom-pom being shaken. Drop this video snow onto the second track and make it fit over the still image.
Next comes the clever bit. Find the Track Matte Key effect and apply it to your video static track. Then, open the Track Matte's properties in the Effect Controls (Premiere Elements 1.0) or Properties (Premiere Elements 2.0) window. For the Matte parameter, choose the video layer with the Photoshop file you created in the previous stage and, for Composite Using, choose "Matte Alpha".
Finally, select your Photoshop file on the timeline and turn down its Opacity to zero. Your subject should now be replaced by video static, add the fades to finish off the effect. Use keyframes and Opacity settings for this. First, fade the empty background on video track four down at the beginning of the "beam down" effect.
Next, fade the video static down slowly across its duration, so the still frame on video track one appears from underneath. To finish, add an appropriate sound to go with the visuals. Then pat yourself on the back - you've boldly gone where no video editor has gone before. Well, almost.