Digital Post Production for Film
A Chapter for the Ninth Edition of The American Cinematographer Manual
by Bill Feightner, Executive Vice President, Technology, EFILM, LLC
Robert L. Eicholz, Vice President, Corporate Development, EFILM, LLC
Computer technology has been used since the late 1970’s to enhance film images in post
production. In 1982, Disney’s breakthrough animated movie Tron (Bruce Logan, ASC)
stunned the film industry by demonstrating just how far digital technology had evolved.
Today, filmmakers and movie-goers alike take sophisticated special effects for granted.
Recently, with the advent of the Digital Intermediate process, digital technology’s impact on
filmmaking has taken another important step forward. This process, in which entire films are
digitized, provides a whole new set of creative tools, allowing cinematographers unprecedented
latitude in controlling and refining the final look of their film images.
A complete description of Digital Post Production for Film would fill many volumes. This
chapter provides a high-level overview, and focuses on current and future industry trends.
REPRESENTATIVE DIGITAL SERVICES OVERVIEW
A large, worldwide industry has formed to serve filmmakers’ digital post production needs. The
digital services offered fall into three broad categories:
1) Acquiring and Digitizing Images
2) Enhancing and Manipulating Digital Images
3) Delivering Images
1) Acquiring and Digitizing Images
To manipulate images in the digital realm, those images must first be converted to industry-
standard digital formats. Traditional film must be scanned, and video-originated material must go
through image processing.
Film Scanning
Film scanning is the process of converting analog film images to the digital realm. Once images
are in a digital format, post-production artists can manipulate them with computers (Figure 1).
Conceptually, film scanners work much like desktop scanners. That is, a light is shined through
each frame and the image captured and digitized on a CCD array, which translates the light into
the computer bits and bytes needed to store and manipulate the image digitally.
The devices currently in use for digitizing film can be divided into two categories: Telecine and
Film Scanner. Both devices allow the film negative to be digitized, though there are considerable
differences. A telecine device runs at real time without mechanical pin registration and is
generally designed to give on-the-fly interactivity while the film is loaded. Most of these designs
FIGURE 1 – Film Scanning (Digitizing)
Digital File
(e.g. Cineon)
Delivery Medium
(e.g, FireWire Drive)
Processed Film
Negative
Film Scanner
(e.g.,ARRIScan)
are based on HD technology and are not able to scan the full resolution, dynamic range, and color
pallet available on the negative film. A true film scanner on the other hand is a stable high quality
digitizer with no interactive controls generally scanning at slower rates allowing the film to be
mechanically pin registered.
The scanning parameters for a true film scanner are set before the film is loaded and are
repeatable across multiple scanner units. They are designed to capture the full resolution,
dynamic range, and color pallet available on the negative film for subsequent manipulation in the
post production process. This is usually done with tri-linear CCD imaging arrays with one for
each color. The combination of the spectral response of the illuminant, often Xenon, spectral
notch filtering, and the response of the arrays, are tuned so that the scanner sees the negative the
same way that print film does in standard laboratory printing.
Other important aspects of modern film scanners technology includes:
Scanning Speeds and Pin-Registration – Because of the need for steady images in
Digital Intermediate and Visual Effects, pin-registered scanners are required for most
applications. Pin-registration mechanisms are designed mechanically to close tolerances,
so that each frame is scanned in exactly the same position as all other frames. This
process reduces or eliminates the “weave” that sometimes results from non pin-registered
scanners. The disadvantage of pin-registered scanners is that they typically scan at
slower rates than non pin-registered scanners. When some degree of image weave is
acceptable, non pin-registered scanners do offer a very fast and economical alternative.
Figure 2 provides a comparison of Scan times associated with various scanners.
In visual-effects, pin-registration of these elements is critical, because effects applications
involve multi-layer compositing of foreground and background elements. Practice has
shown that the critical tolerances of camera and optional-printer movements must be
maintained in the operation of digital film scanners. This registration tolerance is +/-
.0001 inches (2.5 microns) which translates to ? pixel in 4K sampled images. This
ensures that element-to-element registration is transparent to the critical observer. With
the emergence of high quality digital cinema projectors accurate registration on non-
effects shots will be equally important since there is no projector weave to hide non pin-
registered scans.
Resolution – The first generation of scanners generally scanned a 35mm frame at
2K (2048x1566 pixels) or 4K (4096x3112) (Figure 2). A common
misconception is that a high-quality 2K resolution image is scanned at 2K.
According to the Nyquist Frequency Rule, the theoretical maximum resolution a
digital capture devise can resolve is only half of its sampling rate. Therefore, to
achieve a true high-quality 2K can, the film image must actually be “double over-
sampled” at 4K, and then mathematically “down-sampled” to 2K.
Figure 2 – Scanning Rates and Resolutions Table
2K (double oversampled) 4K
Target Digital File Resolution 2048 x 1556
(82 pixels / mm)
4096 x 3112
(164 pixels / mm)
Scan Rate – Current
Generation Scanners
(Pin-registered)
Frame: 2-4 seconds/frame
1000’ Reel: 13.3 hours
Frame: 4-8 seconds/frame
1000’ Reel: 27 hours
Scan Rate – Next
Generation Scanners
(Pin-registered)
<1 Frame/Second
1000’ Reel: 4-5 hours
< 1 Frame/Sec
1000’ Reel: <4-5 hours
Scan Rate – Non-pin-
registered
8 - 24 Frames Per Second
< 20 minutes-1 hour
Dustbusting – Inevitably, even after extensive film cleaning and using scanners in sealed
positive-pressure “clean rooms”, some dust particles are scanned and digitized. These
image flaws are removed in a highly labor-intensive process called “dustbusting”. While
several automated systems help find dust particles, a human being must still examine and
fix every frame to ensure that dust particles to not end up on the final digitized image.
More automated detection processes, based on Infra-Red detection, are on the horizon
(see next section).
Scanning: Next Generation - A radical new design from ARRI will become available
middle of 2004. It will differ significantly from the traditional approaches. It will have
specially tuned LED arrays as the illuminant which matches the response of the negative
film. LEDs with associated control electronics do not have the flicker and stability
problems associated with Xenon or incandescent light sources. It will employ a single
CMOS two dimensional scanning array. While the negative is pin registered in place a
snap shot of the entire negative is taken at one time instead of moving the film past a
single line tri-linear array. The two dimensional CMOS technology is much faster
allowing a single chip to make multi-level RGB samples for increased contrast sampling
ranges and less noise. A forth infra-red channel is included for dirt detection.
Sophisticated internal auto calibration will allow device independent scanning parameters
to be loaded across multiple scanners with the same results.
2) Enhancing and Manipulating Digital Images
Once film images have been digitized, a wide variety of services is available to enhance and
manipulate the images. Some of the most important include:
Color Correction – Digital Color Correction, or Digital Color Timing is the process of
manipulating color digitally to achieve the desired look for film projection, digital projection and
video display. Traditional Color Timing is a photochemical process at the laboratory.
Cinematographers view work prints of their films, and adjust color by “calling lights”, meaning
adjusting the way film is printed to achieve the desired look. In Digital Color Timing, this entire
process is done with computer software.
Digital color correction allows the following benefits over traditional laboratory timing:
? Instant Feedback - In a typical digital color timing session, cinematographers see their
films projected digitally, and instantly see the result of their decisions. By contrast, in
traditional Color Timing, one or more days elapse between the color timing session and
viewing of the results.
? Keying and Matting – In digital color timing keys and mattes provide the ability to apply
different changes across each frame. For example, eyes of a subject can be made
brighter, and then tracked through an entire scene, with the rest of each frame unaffected
by this change. In traditional Color Timing, any changes made must be applied to the
entire frame.
? Additional Options – Digital color timing provides many additional options not available
in traditional Color Timing to enhance images, including image sharpening, defocusing
(smoothing), contrast adjustments, color changes, and others.
Digital Assembly – Traditionally, filmmakers cut their original negatives to assemble their final
film negative. Increasingly, filmmakers submit their original camera negatives to their digital
laboratory. Appropriate selects are scanned digitally with handles. These selects are then
assembled digitally into the final cut, using an electronic Edit Decision List (EDL).
Digital Titles and Opticals – Opticals, such as a fade out from one scene, and a fade in to a
subsequent scene have been traditionally done manually, using complex mechanical devices. In
the digital realm, all opticals can be completed quickly and seamlessly, with the ability to quickly
view the result and make changes.
3) Delivering Images
Once digital images have been a finalized, they can be delivered in various digital and analog
formats:
Film Recording – Film recording is the process of recording digital images on film (Figure 3).
All images are recorded to fine grain intermediate film stocks, either from Kodak or Fuji.
FIGURE 3 – FILM RECORDING
Processed Film
Negative
Film Laboratory
Film Recorder
(e.g.,ARRILaser)
Unprocessed Film
Negative
Digital File
(e.g. Cineon)
Laser technology is currently the only available technology that can completely fill the wide color
gamut, high contrast range, and high resolving power of motion picture film. In the past before
laser technology was readily available, other film recording technologies were used, but they fall
short of today’s demanding quality expectations.
Kodak manufactured the Lightning Film Recorder, the very first laser film recorder. This system
uses three lasers (red, green, blue) to expose film negative in 10 bit log space. This recorder is
still in use today.
With an installed base worldwide of 130 recorders, ARRI Laser currently the sole manufacturer
of laser film recorders. Even with the many advances in this field, film recording is still a
relatively slow process. In fact, with only one recorder, it would take -days to film out an entire
feature film. Figure 3 provides a summary of recording times.
Figure 4 – Laser Recording Table
2K 4K
Target Digital File Resolution 2048 x 1556 full aperture
(82 pixels / mm)
4096 x 3112 full aperture
(164 pixels / mm)
Individual Frame Recording
Time
Frame: 2.1 seconds
Frame: 4.2 Seconds
1000’ Reel (28 minutes)
Recording Time
9.3 hours 18.6 hours
Film (7 full reels) Recording
Time
65 hours (one recorder) 130 hours (one recorder)
The most common resolution for film recording is 2K. However, in July 2004, Sony Pictures
scanned and film recorded Spiderman 2 (Bill Pope, ASC) entirely in 4K at EFILM, LLC in
Hollywood. As disk drive and computer processing costs continue to decline, industry observers
expect 4K to become the new standard.
Another related trend is multiple negatives. Cinematographers using 4K images are
encouraged to consider recording multiple negatives, as any benefits of using 4K resolution can
be eliminated by the traditional Negative – Interpositive – Internegative – Print process and its
associated multi-generational image quality loss (see Future Trends below).
Other Delivery Media – In additon to film, digital images are delivered on a wide variety of
other formats, including:
? Tape (e.g., D5, D1)
? Disk Drives (e.g., FireWire technology)
? Digital Cinema Masters for digital projection (e.g., QuVIS)
? Video Masters (for subsequent conversion to NTSC, DVD, PAL, DVD, and other common
formats)
INDUSTRY SERVICES, PRODUCTS, AND MARKET SEGMENTS
The Digital Post Production services described above are combined into service lines for various
purposes. The most common are Special Effects, Tape to Film, and Digital Intermediate.
Special Effects – Special effects are now included in virtually every motion picture. The
special effects process begins with digitization of original images. Film-originated images are
scanned, generally on a 2K pin-registered scanner (Figure 5). The images are subsequently
manipulated by computer software programs and then output to film. Because of the precise
nature of digital manipulation, use of a pin-registered scanner to produce steady images without
weave is mandatory. Video or 24P-originated images are imaged processed and / or transferred
to the appropriate digital format.
FIGURE 5 – Special Effects
Digital File
Processed Film
Original Camera
Negative
Film Scanner
Image Processing
or
Lab
Processing /
Negative
Digital Image Manipulation
- Compositing / Roto
- CGI
- Color Correction
Film
Recorder
Tape Input
(e.g. HD Cam, 24P)
Even average feature films typically contain 75 – 150 special effects shots. Effects-laden films
can contain 500 –1000 or more shots. A recent trend is toward special effects shots that do not
look like special effects. Common examples include:
? Wire and negative scratch removal
? Addition of rain, snow, and other weather elements
? Changing seasons with color changes
? Changing day scenes to evening scenes
Tape to Film – As a result of the increasing quality and decreasing costs, many independent and
even some mainstream filmmakers now originate on video and digital 24p cameras, rather than
film. Recent examples include Once Upon a Time in Mexico (Robert Rodriguez,
Cinematographer) and Star Wars: Episode II - Attack of the Clones (David Tattersall, ASC).
Like Special Effects, the Tape to Film process involves acquiring images, manipulating and
enhancing them, and recording to film (Figure 6). There is a growing trend at film festivals to
forego the film print and instead project digitally, thus eliminating film entirely. This trend is
expected to continue and expand.
FIGURE 6 – TAPE TO FILM
Digital File
Tape Origination
(eg HD Cam, 24P )
Image Processing
Digital Image Manipulation
- Compositing / Roto
- CGI
- Color Correction
Film
Recorder
Lab
Processing /
Negative
Image
Translation
or
Digital Cinema
Master
(e.g., QuVIS /
QuBIT)
Digital Intermediate – Digital Intermediate uses a comprehensive suite of services to create
Digital Master of entire films (Figure 7). In this process, entire films are scanned (or imported in
the case of 24p digital capture), assembled, color corrected, and then recorded back to film from
the final Digital Master. In addition, the Digital Master is used in a computer-based translation
process to create a video master, which is used to create video and digital cinema masters.
Kodak invented the concept of Digital Intermediate with its Cineon system. This process
envisioned full 2K or 4K pin-registered scans and laser film recording, using the Cineon digital
file format to capture and manipulate film’s full dynamic range. The first digital intermediate
film Pleasantville (John Lindley, ASC) was completed by Kodak’s Cinesite in 1998. Then in 2001
EFILM, LLC in Hollywood completed the world’s first full 2K digital intermediate, We Were
Soldiers (Dean Semler, ASC). This ground-breaking film, which was also the world’s first film to
be completed without traditional laboratory Color Timing, proved that digital intermediate could
produce images acceptable to filmmakers and moviegoers worldwide. Following We Were
Soldiers success, the Digital Intermediate market exploded. By 2004, approximately 25% of the
major Hollywood releases used the Digital Intermediate process. By 2005, this will increase to
approximately 50%.
FIGURE 7 – DIGITAL INTERMEDIATE
High
Resolution
Scan
Digital Mastering Process
Create Digital Opticals
Conform Scans, Vfx,
Opticals to EDL
Dust Bust
Digital Color Time
Title
“The Digital Master”
Video Masters
Laser Record IP
Digital Cinema
Visual Effects 2D / 3D
Off Line Edit: EDL
Telecine Camera
Digital Projection
(Calibrated)
Viewing
TECHNICAL ASPECTS
Image Capture and Standards
Modern motion-picture original negative stocks capture images with red, green and blue records
representing more than an eleven stop scene exposure range. The negative captures more latitude
than can be reproduced on the print. The characteristic curve for the digitized film negative as
well as a projected print film is illustrated in Fig. 8. By adjusting the respective red, green, and
blue printer lights, the lab timer can set the exposure range of the negative that the print will see.
It is important to maintain this extended latitude during the Digital Intermediate process. The
scanner should be zeroed on the D-min of the specific film stock that is being scanned. The
typical industry scanning metric of choice is logarithmic with 10 bits allocated to a 2.0 plus
density range. With a typical exposure, a 90% white card will produce a digital code value of
approximately 685, with 2% black falling at approximately 180 code values. The range of code
values above 685 provides headroom for specular highlights and light sources, or extra latitude
for overexposure in shots that pan or move from shadows to bright sunlight.
FIGURE 8 –RELATIVE LOG EXPOSURE
Rel Log Exp
0
250
500
750
1000
-2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50
1
0
-
b
D
i
g C
ode
Va
l
u
e
Printing Density
Projected Film Print
The color fidelity of the original film images is maintained by digitizing the film in terms of
printing density. In order that the scanner “see” the film the same way in which it was printed in
dailies, the spectral response of the digital film scanner is designed to match that of the motion-
picture print film in standard printer (Fig.9). This ensures that the digital record contains the same
color characteristics as the original negative film. It should be noted that printing density is
similar to (but not exactly the same as) the status M density filters used to measure negative films.
The 10-bit log Cineon digital film format has become the de facto standard for the scanning and
exchange of images between digital film facilities. Digital film scanners and recorders
manufactured by several companies have been designed to this standard. Most of these scanners
FIGURE 9 –SPECTRAL RESPONSE OF TYPICAL DIGITAL FILM SCANNER AND
STATUS M
Wavelength (nm)
0
0.5
1
1.5
2
2.5
3
3.5
350 400 450 500 550 600 650 700 750
S
p
e
c
t
r
a
l
R
e
s
ponc
e
Status M
Scanner
support selectable sampling resolutions of 4096 (4K) or 2048 (2K) across the width of a 35mm
full-aperture image. To understand the impact of sampling resolution on image sharpness, one
can look at the system Modulation Transfer Function (MTF) for a series of sampling resolutions
as shown in Fig. 10. This shows significant MTF gains when going from 1K to 2K, but
diminishing returns as the sampling resolution is increased from 2K to 3K, with very little gain
above 3K. In current practice, most shots are scanned and processed at 2K except when digital
zoom or repositioning is required when a shot might be scanned at 4K and resized to 2K for
processing and final output. Although processing images at 4K is expensive, and while most
additional detail in 4K digital images is lost in film printing and projection, resolutions higher
than 2K for scanning and archiving will ultimately gain momentum. It is important to note the
growing trend of producing multiple digital printing negative which can allow these increased
2K plus resolutions to actually be seen on the cinema screen.
FIGURE 10 –MTF RESPONSE VS> SAMPLING RESOLUTION
Frequency (c/mm)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0204060
R
e
l
a
t
i
v
e
R
e
s
ponc
e
1K
2K
3K
4K
5K
Displaying Digital Film Images
The intent of displaying the digital images is usually to emulate how the audience will see the
final delivered product. Extreme care must be taken to assure accuracy.
Large screen projectors have difficulty emulating electronic display devices. This is because of
film’s inherent wide color gamut, high contrast range, high resolving power, and complex non-
linear inter-color effects due to the complex chemical processes which produces the color images.
CRT displays most often used to date, lack the color pallet available on film and allow only a
subset of the total film colors to be displayed. To make this subset of colors come close to
matching film, complex three dimensional color mappings are needed to impart the non-linear
transfer function of projected film. CRTs are not inherently stabile devices so they must be
calibrated often. Monitors such as those from Barco and Sony have internal stabilization
electronics and built in calibration systems to assure stability. The viewing environment is also
critical and should match the darkened cinema.
Digital projection technology has matured to a point that it can come close to emulating projected
film. To date the DLP TM from Texas Instruments can attain a contrast ratios of over 2000:1 with
a color pallet approaching film. With the extremely stabile digital light valve technology, along
with the built in color management systems, predictable stabile images are assured. Also,
complex three dimensional color mappings are needed to impart the non-linear transfer function
of projected film. The size of the digitally projected image can also match its film counterpart.
Most important when digitally previewing film images is that the entire system be end to end
calibrated, including the film processing laboratory, to assure accuracy. If the images are
destined for delivery to other display venues, then the ability to emulate these devices is
important. If the destination is to multiple display venues, then the ability to translate the look of
the delivered images into each device’s look space is required.
Quality Control and Calibration
Digital filmmaking requires quality control of the end-to-end process to ensure that the digitized
images can be seamlessly intercut with live action. Maintaining the technical specifications of
contrast range, color fidelity, resolution and registration are part of the process. With many of
today’s feature-film productions farmed out to multiple postproduction facilities for visual
effects, the consistency from shot to shot and from facility to facility is also very important. The
best way to achieve this is to standardize on a common file format for interchange and to work
with one service provider for the digital film scanning and recording operations. The Cineon 10-
bit file format has become the current de facto standard for image exchange. Many new file
format standards are in the works and show much promise.
While it is possible with a calibrated monitor to get an approximation of how the final film print
will look on the projected print, different display technologies are needed. In order to achieve
accurate simulation, full closed loop system calibration including the processing laboratory is
required. This includes daily scanner, display, recorder, and sensitometric control of the
processing laboratory. In order for the display device to match a print at a given laboratory,
multidimensional spectrographical characterizations of the resultant negative and print are
required in order to develop multi-demitional lookup tables for the display devices.
INDUSTRY TRENDS
Technical and business process advancements continue to accelerate in Digital Film Post
Production. Some of the more interesting current trends include:
? 2K to 4K: While the difference between 4K and 2K images is subtle to some
moviegoers, there are differences. As a result, 4K is expected to become the industry
standard for mastering and archiving.
? 2K Projection: Many post production facilities and theaters are already converting from
1K to 2K projection with new projectors based on Texas Instrument’s DLP system, such
as Barco’s DP100 and Christie’s CP2000. Because the new 2K projectors offer both
better resolution and contrast (2000:1 plus) at no additional cost over their 1K
predecessors, this trend is likely to accelerate.
? Multiple Digital Negatives: Increasingly, studios are creating multiple negatives for
their features. Using Kodak’s Estar negative, this allows laboratories to strike prints off
of multiple original digital negatives. By contrast, the traditional Negative, IP, IN, Print
process results in three generations of image degredation. By filming out multiple
negatives, all theater prints become “show prints.” The image improvement is
significant, even to less experienced movie goers. This trend is rapidly accelerating,
resulting in a corresponding need for capacity increases at digital post production
facilities.
? Auto-Assembly: Early digital intermediates were scanned from cut negative. For many
features, this is no longer true. Increasingly, production companies submit EDL’s, which
are used to electronically assemble scanned selects. A side benefit of this process is that
because the negative is not handled in an editing room, the film is less vulnerable to dirt,
dust, and scratches.
? Digital Cinema Previews: With the advent of auto-assembly, and quality 2K digital
projection, some studios are electing to do a series of digital cinema previews prior to
locking their films. Using revised EDL’s, features can be re-edited, re-color corrected,
re-assembled and then previewed digitally at multiple locations.
? Reduced Special Effects Costs: Recent significant reductions in special effects tool
costs have reduced overall costs for visual effects. Tools such as Discreet’s Inferno,
operating on SGI IRIX hardware are still common throughout the industry. However, a
new generation of PC-based tools such as Apple’s Shake, with powerful PC-based
renderfarms such as Apple’s Xserve promise quantum leaps in price-performance.
? Digital Archiving: As the number of digital masters increases, so does the need to
consider the archiving implications. Unlike film, digital masters on tape are vulnerable to
changing technologies rendering formats obsolete and possible corruption of digital files.
Studios are researching the best approaches to ensure that their digital assets can be
preserved just as long as their archived film. Because this is a technically complex issue,
many industry groups and corporations are working standards and solutions. Within the
next few years, a new generation of companies and services will evolve to serve the
digital archiving needs of studios.
Bill Feightner, Executive Vice President, Technology is an Associate Member of the ASC. Mr.
Feightner was one of the founding owners of EFILM, and is in charge of envisioning,researching,
developing, and implementing all aspects of EFILM’s Digital Laboratory Services.
Robert L. Eicholz, Vice President of Corporate Development at EFILM, oversees management
and operation of EFILM’s technical groups, including software development, engineering, and
imaging.
This chapter contains several excerpts from a similar chapter written by Glenn Kennell (Director
of Technology Development, Texas Instruments DLP Cinema) and Sarah Priestnall (formerly of
Kodak’s Cinesite) for the previous edition of the ASC Handbook.
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