Nelson Zagalo from the University of Minho in Portugal gave a presentation on compositing at the University of Maribor in Slovenia. Compositing involves combining visual elements from different sources to create a single image, often making elements appear part of the same scene. It is used for special effects in film and to connect real and artificial images. Traditional film techniques included physical compositing, multiple exposures, rear projection, and matting. Digital techniques include blend operations, keying, alpha channels, mattes, masks, nesting, color correction, and motion tracking. Zagalo provided examples of how these techniques have been used in famous films.

1. Universidade do Minho
Compositing, composing worlds
Nelson Zagalo, University of Minho, Portugal
13th May 2011, University of Maribor, Slovenia

2. Nelson Zagalo
Contact me
nzagalo@ics.uminho.pt
www.facebook.com/nelsonzagalo
My Work
nelsonzagalo.googlepages.com
www.engagelab.org

3. Film Compositing
King Kong (1933) Superman (1978)

4. Defining compositing
What is it?
Compositing is the combining of visual elements
from separate sources into single
images, often to create the illusion that all those
elements are parts of the same scene.
What do we use it for?
. to create special effects in visual arts;
. to help us connecting real images with
artificially created ones;
. to correct photographic mismatches (e.g.
color);
. to change or substitute backgrounds;
. to change or substitute foregrounds;
. to create illusion of depth.

5. Compositing techniques
Film (analogical)
1. Physical compositing
2. Multiple exposure
3. Rear projection
4. Matting
Digital
1. Blend Operations
2. Keying
3. Alpha Channels
4. Mattes
5. Masks
6. Nesting
7. Color Correction
3d Compositing
8. Motion tracking and match moving

6. F1. Physical - Glass, Statues, Paintings
The Fiendish Plot of Dr. Fu Manchu (1980)
Clash of the Titans (1981)

7. F2. Multiple exposure
Multiple exposure of Alfred Hitchcock directing during
rehearsals for Shadow of a Doubt (1943).
video
L´Homme Orchestre, George Melies, 1900

8. F3. Background projection
North by Northwest, 1959
2001, Space Odyssey, 1968
Sunset Boulevard, 1950

9. F4. Matting
The Birds, 1963 video

10. Compositing techniques
Film (analogical)
1. Physical compositing
2. Multiple exposure
3. Rear projection
4. Matting
Digital
1. Blend Operations
2. Keying
3. Alpha Channels
4. Mattes
5. Masks
6. Nesting
7. Color Correction
3d Compositing
8. Motion tracking and match moving

11. Digital Advantages
video
Omaha beach scene “making of”, belonging to the BBC series “Timewatch:
Bloody Omaha”. Created by Colin Thornton, Neil Wilson and Steven Flynn
from Compost Creative.
3 persons + 4 days + 1 camera + pop up greenscreen + after effects

12. D1. Blend Operations
Multiply
Screen
Overlay
Darken
Lighten
Difference
Exclusion
Luminosity

13. D1. Blend Operations

14. D2. Keying
AE: Color Key, Edge Thin, Color Tolerance, Luma Key, Matte Choker
Color Key
Luma Key
Edge Thin
Color Tolerance
Matte Choker

15. D2. Keying
The Chronicles of Narnia (2005)
King Kong (2005)

16. D2. Keying
Preserve
reflexes
The Saint (1997)

17. D3. Alpha
32-bit image carries a fourth Alpha channel that stores transparency (or
alpha) data. The alpha channel’s 8-bit data is reserved to give an image or
video clip shape and transparency when composited.
Software as Photoshop creates content on transparent backgrounds
retaining background transparency when imported into motion applications.
This is because an alpha channel matte is automatically generated.
Object on
Alpha Channel Final composition
transparency

18. D3. Alpha

19. D4. Matte
Luma Mattes
luma mattes
External image that is used to make portions of another
image transparent. Luminance mattes should not be
confused with alpha mattes, which are internal mattes that
are derived from alpha channels.
Both alpha channel mattes and luminance mattes can be
composed of solid shapes, feathered
shapes, gradients, typography, entire images.
solid mattes
feathered mattes

20. D4. Matte
video

21. D5. Masks
Masks are defined by splines - paths that consist of interconnected
points that form a line segment or curve, around the subject, an art also
knoww as Rotoscoping. Masks can be animated.

22. D5. Masks
Forrest Gump (1994)
video

23. D6. Digital Color Correction
Color grading is the process of altering and enhancing the color of a motion picture, television
image, or still image either electronically, photo-chemically or digitally.

24. D6. Color Correction
High Dynamic Range images
Before After
High Dynamic Range images (HDRi) are a set of techniques that allow a greater dynamic
range of luminance between the lightest and darkest areas of an image than current standard
digital imaging techniques or photographic methods
Mente Magica - http://mentemagica.com/wp/2009/12/31/hdr-reactor/

25. D7. Nesting and Parenting
Nesting – means building compositions and put them inside other compositions.
nesting

26. D7. Nesting and Parenting
Parenting - permits the association or control of animation settings through different layers.
video
Parenting
From “Animated type tutorial 3: anchor points and parenting”, by Gareth Smith, http://vimeo.com/22582326

27. Compositing techniques
Film (analogical)
1. Physical compositing
2. Multiple exposure
3. Rear projection
4. Matting
Digital
1. Blend Operations
2. Keying
3. Alpha Channels
4. Mattes
5. Masks
6. Nesting
7. Color Correction
3d Compositing
8. Motion tracking and match moving

28. D8. Motion track and match moving
Motion tracking and Match moving, are techniques that allow the insertion of computer
graphics into live-action footage with correct position, scale, orientation, and motion relative to
the photographed objects in the shot.
video video
2d Tracking – track objects only 3d Tracking – track camera position
Can be done in After Effects. It’s different from
Parenting in the sense that parenting only synchronizes
layers, albeit Tracking synchronizes content within the
image.

29. D8. Motion track and match moving
It is not related with motion capture, and needs special software as Boujou or NukeX to
extrapolate three-dimensional information from two-dimensional photography. Tracking
information is then transferred to computer graphics software such as Cinema 4d, 3ds Max
or Maya and used to animate virtual cameras and CGI objects.
video video

30. D8. Match moving
video

31. Compositing break down for "The Third & The Seventh", a short-film entirely modeled in 3d, which has gone
through intense compositing.

32. Bibliography
Ron Brinkman, Art & Science of Digital Compositing, Morgan Kaufmann, 2008
Richard Rickitt, Special Effects: The History and Technique, Billboard Books, 2007
Krasner, J., Motion Graphic Design: applied history and aesthetics, Elsevier, 2008
References
Leow Wee Kheng, Digital Compositing, CS5245 Vision and Graphics for Special Effects, National University of
Singapore, www.comp.nus.edu.sg/~cs5245/lecture/compositing.pdf
Matte Shot - a tribute to Golden Era special fx - http://nzpetesmatteshot.blogspot.com/2010/11/leigh-took-matte-
painter-portrait-of.html

33. Universidade do Minho
Compositing, composing worlds
Nelson Zagalo
nelsonzagalo.googlepages.com
engagelab.org