Shooting a real explosion in full scale or even with the use of miniatures generally adds realism to a movie’s special effects requirements.
In the past, it is almost always necessary to create practical explosions to mount scenes showcasing blasts, bombings, fires, and other elements. However, the safety, environmental, and financial issues involved in making them often result in filmmakers having second thoughts on adding explosion shots in their movies.
Now, film technology already makes it accessible and easy for productions to have safer options when producing these effects, making it unnecessary to film actual explosions.
Chroma Shooting and Post-Production Requirements
Making explosion effects for movies often requires the use of a chroma screen background where characters and other practical props and sets are placed in front of either a blue or green screen. This can be a large, flat, solid-colored board, wall, or fabric that should cover the entire background area of the visual elements seen on frame.
Some prefer making chroma backgrounds on their own, while others would rather buy them in photography and videography stores or online shops. A chroma shoot’s blue or green background gets replaced by the explosion footage by using basic chroma-keying techniques in a video-editing program such as Avid Media Composer, Final Cut Pro, or Adobe Premiere Pro. Supplemental programs for making visual effects or using ready-to-use explosion footage are common as well.
Source Materials for Explosion Footage
A source material for explosion footage may need the staging of a real-life explosion set in a controlled environment. The footage is then used as a background for the separate shot of the actors and other foreground elements.
Another option requires acquiring available footage of a real or computer-generated explosion through purchase, free download in a stock footage website, or as part of the video library of visual effects or animation software. Some filmmakers prefer digitally creating an explosion scene on their own by using a visual effects or animation software. This CG image is essentially a photorealistic rendition of an artist’s imagination of a real explosion.
A number of computer programs also allow artists to manipulate readymade explosion footage to suit the enhancements and visual flair their projects need. It is always important to note that although it is easy to find source materials for explosion scenes online or in other movies’ DVD and Blu-ray copies, using copyrighted materials without the consent of the owners is illegal and punishable by law.
Basic Post-Production Workflow
There are many different workflows filmmakers can choose from when finalizing the explosion scenes in their movies. A basic option requires importing both the explosion and chroma-shot clips into a video-editing program. The explosion footage should be placed on the editing timeline’s video track right above the track where the chroma footage is placed. Depending on the software and explosion footage used, an alpha channel may automatically be activated or the editor must create one using any applicable function in the software.
This alpha channel works as a hidden track of data that tells the program which pixels in a video file must be made transparent. Once the green or blue background is changed into the explosion scene, the edited video’s image attributes can now be properly adjusted to fit the best shot composition for the explosion scene.