VISUAL QUICKPRO GUIDE PINNACLE LIQUID EDITION 6 FOR WINDOWS [Electronic resources] نسخه متنی

Using Chroma Keying

There are a number of different names for chroma keying including the more familiar blue- or green-screen compositing.

You often see this on national TV when the weather appears on a screen behind the weather person. In fact, the presenter is pointing to a blank green or blue screen and is looking at an image on a monitor in front of him or her.

Blue-screen compositing is used extensively in movies to put objects and people into a shot. This is what allows Superman to fly and Spider-Man to spin webs around the city without either of them having to dangle from a helicopter.

To create a chroma-based video clip, you need some fairly special equipment; just having a blue or green background isn't really enough to produce truly professional results. First, you must have the correct lighting to remove shadows and to allow the background to be a uniform shade of blue or green. If you don't do this correctly, the composite suffers from strange areas on the screen that appear to glimmer slightly as the light moves inside the shot. A modern audience will spot these and when they do, your effect falls flat.

However, once you successfully shoot the clip and Liquid Edition captures it, the process of removing the green or blue color background is simply a matter of applying a filter and adjusting the parameters for maximum effect.

The following task-based description refers to any of the chroma keying filters, including the Blue Screen, Green Screen, Chroma Key CPU, and Chromakeyer YUV effects.

To apply one of the chroma key filters

Tip

• To work correctly, the clip with the chroma key filter must be the uppermost clip on the Timeline tracks.




Figure 14.35. Adding a chroma filter to the Timeline.




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To use the Blue or Green Screen filters



Figure 14.36 ).

Figure 14.36. The Green Screen Key parameter interface. This is a Realtime filter.






Adjusting the threshold produces the most noticeable difference when you're fine-tuning your chroma effect, but don't ignore the other settings as you adjust this clip (Figure 14.37 ).

Figure 14.37. Before and after adjusting the Green Screen parameters.







Chapter 9.

To use the chroma key filter

Tips

• Hold down the Ctrl key and left-click in the drawn area to move it around (Figure 14.39 ).

  Figure 14.39. Hold the Ctrl key to move the selection area.

  
  

  

• Hold down the Alt key and draw inside the area to subtract areas from your original drawing.

• Hold down the Shift key to add to the areas of your original drawing.

To use the Chromakeyer YUV filter

Tip

• The disc parameter expands the selection area of the color picker.