True blue

From multi-million-dollar movies to student shorts, bluescreen work is now one of the most important tools in the visual effects artist's armoury. The technique allows a filmmaker to shoot foreground action against an evenly lit coloured background - usually blue or green - then replace these background areas with another image during compositing. While this second image can be a live-action plate, the technique is now commonly used to integrate actors and sets seamlessly into an all-CG environment. The technique was recently taken to its natural conclusion in movies such as Sky Captain and the World of Tomorrow, in which all the action was shot against coloured screens, which were then replaced with digital backgrounds.

But while all that is actually required for the technique is a length of blue fabric and a desktop compositing package (for details, see our 'Bluescreen on a budget' tutorial from issue 60, or download it here), to achieve truly polished results requires skill and experience.

So this month, we've asked three VFX artists to provide their tips for creating better blue and greenscreen effects. We'll start by answering one of the questions most commonly asked about this kind of work - what determines the choice of a blue or green screen in the first place, and can you use other coloured backgrounds? - before moving on to crucial considerations such as lighting setup, screen placement, and ways of avoiding pitfalls such as unwanted reflections and colour spill. On the way, we'll be revealing a number of tricks of the trade, such as using reflective foil on the floor of a set or employing a waveform monitor to check the evenness of the lighting on the screen. Finally, we'll look at those situations in which it's best to avoid bluescreen work entirely and rotoscope footage by hand.

Spanning the entire course of a shoot, from creating the set to processing the resulting footage, these production-proven techniques should prove applicable for a wide range of projects, and for an equally wide range of budgets - from independent shorts to professional ad, film and promo work.

Click here to download the tutorial for free