Matakuliah
Tahun
: UO666 / DKV Visual FX
: 2009
The Art Of Compositing 01
Pertemuan 06
Digital Keying
Keying is such a vital area of visual effects,
research continues to both improve the
quality of the key and easy of use of the
module.While it is not strictly keying in
the greenscreen sense - there are a
host of new matte generating tools that
extract mattes via a range of different
technologies.
Bina Nusantara
Green or Blue?
The age old question is should one shoot against
blue or green screen. Many factors influence
the decision, the most obvious being what
colours are represented in the foreground
subject. For a while prior to the Vision 2 stocks
- the film stock itself was grainier in the blue
channel, and hence green screen grew in
popularity. One urban myth is that human skin
contains a lot more green than blue and so
blue screen should be better, in fact this is
only true of blond hair - which is often better
shot against blue - but human skin while not
equally balanced in its green and blue
components - easily keys from either blue or
green screen.
Bina Nusantara
The State of the Art Technology by
Zmatte
The standalone Zbig Software was available on the market since 1998 as
a chroma key/compositing program and as a plug-in for many standard
programs, (Fusion, Illusion and others)
A unique feature of Zbig Software is the automatic and dynamic
application of background color reflections onto the composed
foreground, resulting in an extremely convincing composition.
Bina Nusantara
The State of the Art Technology by
Keylight
The keyer is effectively a colour difference keyer, so it works better on primary colour, and
according to the Foundry's Bruno Nicoletti "to work well it needs a high primary saturation"
in the keying background. Keylight's strength comes from the algorithm that allow the spill
removal to become an intrinsic part of the process. Recently, it has been upgraded to a full
float implementation on Shake, but this is only currently as a plugin. The version shipping
with Shake 4 now respects Float and no longer clamps to 16 bit. Even with Keylight's great
foreground colour correct, in a floating pipeline in Shake, it is often only used for key or
matte generation and not for the key & comp of the foreground and background. The work
of CFC in pioneering their compositing pipeline caused them to get a technical
achievement award in 1996. Keylight anecdotally is thought to be best on transparent items
such as sheer fabric - glass ware and say soft hair. There is now Linux & Burn support for
Keylight. When using the Keylight controls fg bias work best with near neutral colours.
Nicoletti has also written a great new 64 bit version of Keylight for Discreet (A M&E)
products which also has improvements to the matte processing and colour correction tools.
Bina Nusantara
The State of the Art Technology by
Primatte
Primatte today runs on a wide variety of OS - LINUX, OSX, NT IRIX etc.
Primatte is one of the most widely available plugin keyers, from Flame,
Smoke to Fusion, Shake, Quantel, AE, Photoshop, Nuke and others.
When using Primatte's controls the fgbias effect the f/g colour & Matte
opacity, the key controls are the shadow gain, mid gain and highlight
gain.
For a full discussion of Primatte listen to our fxpodcast with Scott Gross of
IMAGICA Corporation of America by clicking the links at the top of this
page. Scott has been involved with Primatte from the beginning and he
explains not only the keyer's approach but much of its history.
Bina Nusantara
The State of the Art Technology by
Ultra Keyer (Fusion keyer)
- Five modes of spill suppression to eliminate difficult reflection halos.
- Animated garbage mattes for isolating rigging and set elements.
- Adjustable edge gamma and fringe color correction.
- Matte thresholding for semi-transparent region replacement.
- Matte blur, gamma, and contrast control for post key processing of the
matte.
- Advanced color selection includes a more varied range than traditional
"select" and "soften" style keyers
Bina Nusantara