Study on Chroma Key Shooting Formats

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The Quebec Film and Television Council (QFTC) is pleased to present the results of its study on shooting in different formats against colour backgrounds. The study involved 18 QFTC member organizations. This form and level of participation represents a real first for the industry, not only in Greater Montreal, but in Quebec and internationally as well. Throughout the course of our work, we were truly impressed by the devotion of the organizations involved in helping us meet the formidable challenge posed by this mandate. Over a period of 10 months, they participated actively in the shooting and postproduction phases, dedicating their personnel to testing the integration of computer-generated images into 350 mini-clips. The present document presents a detailed review of the processes employed in each phase of the project — from the original idea, through its execution and conclusion. We sincerely hope that the findings will help the Quebec visual effects industry enhance its competitiveness on the international scene. The knowledge gained will also be transferred via various academic training programs. Thus, current VFX professionals and those preparing to enter the sector will all have ready access to this new body of knowledge. In conclusion, I would like to take this opportunity to underline the quality of the work accomplished by the entire team, as well as to thank the financial backers who provided us with their invaluable support throughout the course of this project. Hans Fraikin National Commissioner and Executive Director of the Cluster

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Thanks to all our collaborators!

Public Contributors

Private Contributors With the support of:

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Table of Contents

SUMMARY ..................................................................................................................................................... 8

INTRODUCTION ........................................................................................................................................... 10

PROJECT OBJECTIVES .................................................................................................................................. 10

GENESIS OF THE PROJECT ........................................................................................................................... 10

TECHNOLOGICAL FRAMEWORK OF THE PROJECT ...................................................................................... 11

1. cameras ........................................................................................................................................... 11 A. Film Camera ................................................................................................................................ 12 B. Digital Camcorders (multi-sensor) .............................................................................................. 12 C. Digital Camcorders (single-sensor) ............................................................................................. 12 D. Framing ....................................................................................................................................... 13 E. Recording Formats ...................................................................................................................... 13 F. Recording Media ......................................................................................................................... 13

2. COLOUR BACKDROPS ...................................................................................................................... 14 A. Choice of Colours ........................................................................................................................ 14 B. Choice of Light Source ................................................................................................................. 15 C. Subject (foreground) ................................................................................................................... 15 D. Plate (background) ...................................................................................................................... 15

3. SHOOTING METHODS ..................................................................................................................... 16 A. Lighting ........................................................................................................................................ 16 B. Shot Exposure ............................................................................................................................. 16 C. Shooting Sequences .................................................................................................................... 16 D. Exposure and Duration of Sequences ......................................................................................... 17

METHODOLOGY .......................................................................................................................................... 18

1. FILM PROCESSING ........................................................................................................................... 18 2. DIGITAL DATA MANAGEMENT ........................................................................................................ 18

A. Digital Format.............................................................................................................................. 18 B. File Format .................................................................................................................................. 18 C. Distribution Media ...................................................................................................................... 18

3. Compositing .................................................................................................................................... 18 A. Analysis Grid ................................................................................................................................ 19 B. Evaluation Scale .......................................................................................................................... 19 C. Software Employed ..................................................................................................................... 20 D. Collection of Results .................................................................................................................... 20

RESULTS ...................................................................................................................................................... 21

* THIS SECTION SECTION IS AVAILABLE ON REQUEST FOR QFTC MEMBERS ONLY ........................... 21 AND AT THE RATE OF $ 500 FOR NON-MEMBERS .............................................................................. 21

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CONCLUSIONS ............................................................................................................................................. 21

* THIS SECTION SECTION IS AVAILABLE ON REQUEST FOR QFTC MEMBERS ONLY ........................... 21 AND AT THE RATE OF $ 500 FOR NON-MEMBERS * ........................................................................... 21

APPENDIX 1 – Participants AND CONTRIBUTORS ....................................................................................... 22

APPENDIX 2 – TECHNICAL CAMERA DATA .................................................................................................. 25

APPENDIX 3 – RECORDING FORMATS AND MEDIA .................................................................................... 26

APPENDIX 4 – ANALYSIS PROTOCOL ........................................................................................................... 27

1. TEST SET .......................................................................................................................................... 27 2. nomenclature .................................................................................................................................. 28 3. ANALYSIS PARAMETERS .................................................................................................................. 29 4. SCORING .......................................................................................................................................... 29 5. DETAILED ANALYSIS ........................................................................................................................ 30

A. Matte Density ............................................................................................................................. 31 B. Contour Detail ............................................................................................................................. 32 C. Light on the Contours ................................................................................................................. 32 D. Grain or Noise ............................................................................................................................. 32 E. Occlusion ..................................................................................................................................... 33 F. Transparencies ............................................................................................................................ 33 G. Suppression ................................................................................................................................. 34 H. Colour Space ............................................................................................................................... 34

APPENDIX 5 – RESULTS TABLES ................................................................................................................... 35

* THIS SECTION SECTION IS AVAILABLE ON REQUEST FOR QFTC MEMBERS ONLY ........................... 35 AND AT THE RATE OF $ 500 FOR NON-MEMBERS * ........................................................................... 35

Team list ...................................................................................................................................................... 36

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SUMMARY

Since the 1930s, the film and television industry has developed numerous techniques to “key”

an action shot in the studio into a virtual “set”. Initially known as “travelling matte”, the

technique gave rise to a number of technological developments that have allowed for the

production of major cinematographic works over more than 80 years.

Whether it is a matter of journeying in outer space, coursing through the human body, or

transporting our screen idols to exotic or perilous places, the quality of the keying, and

consequently, the “credibility” of the sequence is the product of a series of processes carried out

on the film or TV set, as well as by the postproduction and visual effects artists and technicians.

For this project, we have decided to review a selection of theses methods by creating a

sequence that reunite the most complex elements of a shoot on colour backdrops.

In view of the advancements made over the past five years with respect to cameras and image

compositing systems, we felt it was essential to put things into perspective by incorporating all

the variables that could affect the quality and effectiveness of shooting against colour

backdrops. Considering that this visual effects technique is more and more required, it seemed

important to us to test the various shooting methods (based on background colour, camera

type, type of lighting, etc.) in order to understand their impact on the expected screen results.

Over 350 scenes were shot under the direction of Director of Photography Daniel Vincelette and

Visual Effects Supervisor Jacques Levesque.

Eight different cameras were used to shoot the short sequences that, once recorded on

recognized digital media, went through the postproduction process to create the final

composited images.

Each of the scenes was subject to careful prior analysis in accordance with specifically defined

criteria by more than 15 Quebec postproduction and visual effects companies. Every sequence

was evaluated and classified so as to determine the shooting quality and ability to readily

produce a final high quality chroma-key.

With the diversity of technologies offered to today’s producers and creative personnel, it has

become important to conduct an objective review of the processes available and to provide the

rest of the film community with an up to date picture of where we are in the application of

techniques for creating images shot against colour backdrops.

This exercise enabled us not only to confirm the most beneficial and effective shooting practices,

but it also demonstrated the importance of precision and consistency when shooting, regardless

of the camera being used. At the same time, we were able to validate certain characteristics of

digital equipment that could influence the quality of the final result.

We are confident that the information contained in this report will enhance the knowledge of

craftspeople and technicians when it comes to shooting against colour backdrops. Our intention

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is also to provide them with a reference document that will help them better understand the

impact of equipment choices and to weigh the consequences of those choices on other

processes. Finally, our aim is to sensitize producers and managers to the importance of the work

carried out during a shoot, as well as to its effect on the desired results and production costs.

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INTRODUCTION

Greater Montreal has earned worldwide recognition for the expertise of its artists working in

the digital visual effects sector. In fact, a number of our craftspeople and companies have

been nominated for prestigious Visual Effects Society Awards for their work on such

successful films as Journey to the Center of the Earth, 300, The Fountain, Imax Sea Monsters,

Race to Mars, as well as the Quebec TV series, Marie-Antoinette.

This talent in the field of digital visual effects constitutes a significant asset for the

development of this industry and for positioning it on the world stage. Thus, we must

continue to work to maintain the industry’s competitive edge by rigorously stimulating

innovation.

The execution of a research and innovation project on shooting against colour screens is

the first stage of this major initiative. Taking the form of a consortium, this project involves

numerous industry players to concretize technological advancements. At the same time, it

will serve as an opportunity to test the method of innovation in partnership while acquiring

valuable new knowledge.

PROJECT OBJECTIVES

The primary objective of the study is to evaluate the best exposure ratio between

foreground and background when shooting against colour backdrops, based on colour,

lighting, the medium, and the type of sensor used.

In addition, the aim is to produce a reference document for companies and visual effects

craftspeople describing the best processes and combinations.

GENESIS OF THE PROJECT

The project stems from Jacques Levesque, who, in 2009, had the idea of producing a

reference document that could help craftspeople in the production and visual effects sector

understand the role of different variables in play when shooting sequences against colour

backdrops.

In order to accomplish this, players from the production, postproduction and visual effects

fields would all need to be involved.

The list of project participants can be found in APPENDIX 1 and includes:

companies and individuals who have contributed to and participated in the

development and coordination of this project

companies and individuals who have contributed to or participated in the

development and production of images

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companies and individuals who have conducted tests and created chroma-keys using

shot material

TECHNOLOGICAL FRAMEWORK OF THE PROJECT

In view of the scope and complexity of the various technologies generally used within the

visual effects and film production industry, it was necessary to create a working framework

that could effectively generate the desired results. To that end, the project team had to

make a certain number of choices with respect to the nature of the technologies employed

and the scale and orientations of the tests to be conducted.

1. CAMERAS

Since visual effects in professional productions call for a large variety of camera types, we

selected digital cameras of various types, as well as a film camera (35 mm) to shoot the

images and sequences for this project. Each of these cameras feature characteristics

representative of the technologies most likely to be used for shooting sequences against

colour backdrops intended for the production of visual effects.

Following is a list of the cameras selected:

CAMERA CHARACTERISTICS

ARRI 435 We shot with a 1:78 aspect ratio on three types of film

Sony PMW-EX3 Camcorder equipped with three ½ in CMOS sensors

Panasonic AJ-HPX3700 Camcorder equipped with three 2/3 in CCD sensors

Sony SRW-9000 PL Camcorder equipped with a single 35 mm CCD sensor

ALEXA Digital camera equipped with a single 35 mm CMOS sensor

RED ONE Digital camera equipped with a single 35 mm CMOS sensor

Phantom HD Gold Digital camera equipped with a single 35 mm CMOS sensor

ARRI D-21 Digital camera equipped with a single 35 mm CMOS sensor

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A. Film Camera

The film camera selected for the purposes of the project was the ARRI 435. The determining

factor for the conventional shooting rests essentially on the choice of film type. We were

looking for both a tungsten-balanced, medium sensitivity film stock and a high-sensitivity

film in order to measure the consequences of sensitivity on the rendering of composites in

postproduction.

Because some shooting against colour backdrops is also done in daylight, we selected a

daylight film as well.

B. Digital Camcorders (multi-sensor)

We chose equipment with sensors not smaller than ½ in. We also favoured sensors with

native resolution of at least 1920 x 1080 pixels.

We included both CMOS and CCD technology in order to assess whether these two types of

sensors react similarly in demanding situations like shooting against colour backdrops.

Note: We deliberately excluded certain types of digital equipment to limit the scope of the

project and avoid testing too many cameras given the constraints on our time and resources.

Thus, the digital camcorders or cameras that use sensors of less than ½ in did not appear to

us to meet the criteria of this study, which is focused primarily on large-scale projects that do

not generally tend to make use of that type of equipment.

C. Digital Camcorders (single-sensor)

These cameras are equipped with a single sensor that employs Bayer Pattern technology or

RGB Stripe colour filtration. The large size of the sensors used in these cameras (35 mm or

more) coupled with native resolution that generally exceeds the conventional 1920 x 1080

makes these cameras particularly apt for shooting against colour backdrops, and we selected

three distinct types that are representative of what is currently available on the market.

Note: The single-sensor digital cameras used for this shoot were equipped with sensors

employing CMOS or CCD technology.

Despite the fact that they are fitted with large-size sensors, we nevertheless excluded HDSLR

models because of the recording codec used in this equipment (AVCHD, long GOP, 4:2:0),

which does not meet the qualitative requirements of professional projects calling for colour

backdrops.

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D. Framing

We opted to restrict shooting to the 16:9 (1:1.78) aspect ratio. Consequently, the focal

length of the lens used on each of the cameras was selected so as to produce an image

within which objects were essentially the same height, regardless of the sensor size. A focal

length of 32 mm was used for single-sensor cameras, as well as for the film camera. A focal

length of 10 mm was chosen on the PMW-EX3’s zoom lens, while a length of 14 mm was

used for the AJ-HPX3700 2/3 in camcorder.

Other considerations:

The focus distance for all cameras was 15 feet.

The height of the camera was 39 inches.

The cameras were tilted up at an angle of 5 degrees.

E. Recording Formats

We selected a range of recording formats for digital cameras that feature the most

frequently sought after characteristics when shooting against colour backdrops.

Because certain cameras offer different forms of colour encoding and operate in linear or

logarithmic mode, we believe we chose the most representative and pertinent methods for

this type of shooting. The table in APPENDIX 2 illustrates our choices for each of the cameras

used.

F. Recording Media

Film Camera: We selected three types of film stock that are representative of the emulsion

types most likely to be used for special effects shoots involving colour backdrops.

FILM ISO CHRACTERISTICS

Kodak Vision3 5213 200T 200 Tungsten – 85 filtration for daylight sequences

Kodak Vision3 5219 500T 500 Tungsten – 85 filtration for daylight sequences

Fuji 8563 250D 250 Daylight – Used with daylight only

Multi-Sensor Cameras: We selected the following recording media:

CAMERA ISO MEDIUM

Sony PMW-EX3 400, 540 for daylight green screen SxS memory card and KiPro disc

Panasonic AJ-HPX3700 500, 640 for daylight green screen P2 memory card and KiPro disc

Sony SxS memory cards were used for the PMW-EX-3 camcorder and Panasonic P2 memory

cards for the AJ-HPX3700 camcorder for reference purposes only. Given the importance of

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4:2:2 encoding, and in order to standardize the digital recording media, we recorded the

sequences simultaneously on KiPro disc in ProRes 422 (HQ) format via the HD-SDI outputs of

the two aforementioned cameras.

Single-Sensor Cameras:

CAMERA ISO MEDIUM

Sony SRW-9000 PL 500 HDCAM-SR tape

ALEXA 800 SxS memory card

RED ONE 800 Compact Flash card

Phantom HD Gold 200 CineMag

ARRI D-21 200 HDCAM-SR tape

For the five single-sensor digital cameras (SRW-9000PL, Alexa, RED ONE, Phantom HD Gold

and D-21), we limited our choice of media to what is recommended by the manufacturers. As

such, the RED ONE uses the Compact Flash card, while the Phantom HD Gold employs

CineMag memory. In the case of the Sony SRW-9000PL, ARRI Alexa and the ARRI D-21, we

used the HDCAM-SR cassette. For the Alexa, we also recorded on SxS cards with Apple’s

ProRes 422HQ codec for reference purposes only.

AJ-HPX3700 ARRI Alexa SRW-9000PL Phantom HD Gold

RED One ARRI D-21 Arri 435 PMW-EX3

2. COLOUR BACKDROPS

A. Choice of Colours

Colour backdrops are primarily blue or green.

Consequently, we conducted all tests with these two

colours. Blue and green (Digital Blue / Digital Green)

canvasses were mounted on frames measuring 20 ft x

40 ft. All sequences were shot against a green backdrop

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during a single shooting session, and all scenes against the blue backdrop were shot during a

second session.

B. Choice of Light Source

Colour backdrops can be lit with artificial light (3200K tungsten) or daylight (5500K film /

5600K video), and these two forms of illumination (tungsten and HMI) were used on both

the blue and green backdrops. In addition, we employed Kino Flo Green 525 and Blue 420

lights to complete the tests in order to measure the impact of this narrow-band lighting,

which is supposed to contribute to the uniform dispersion of the light on the backdrop.

C. Subject (foreground)

There was a separation of the foreground from

the background of approximately 20 feet so as

to be able to light the background as needed

with sources distinct from the foreground (i.e. in

the case of UltraGreen and UltraBlue lighting)

without affecting the subject in the foreground.

The elements in the foreground were lit with

artificial light (3200K tungsten) for the shots in

tungsten light (UltraGreen and UltraBlue), and they were lit in daylight (5500K film / 5600K

video) when the background was illuminated in daylight.

The test set contained a certain number of elements that allowed us to qualitatively analyze

the ease of chroma-keying based on exposure variations. These elements include:

a slowly turning fan a white curtain hung on a frame a frosted panel a finely perforated panel two vases containing orange/yellow tinted liquid grey and colour chip charts a table identifying the test variables (camera, light source, exposure) two subjects (black male and white female) a wide red frame delineating the sampling zone

D. Plate (background)

An image including various elements

allowing for the evaluation of the quality

of the final composition with the

foreground (keying/compositing) was

selected prior to shooting.

In order to facilitate the compositing and

keying work, we placed a frame above the

subjects during shooting that identifies

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the background measurement area for the artists who have to do the compositing work

during postproduction. In so doing, our aim was to standardize the parameters for measuring

background density.

3. SHOOTING METHODS

A. Lighting

The following three types of lighting sources were used:

3200K Tungsten (quartz)

5600K Daylight (HMI)

KinoFlo (Kino 420 blue and Kino 525 green lights)

B. Shot Exposure

The primary interest of this project was to measure the impact of the exposure variation

between the foreground and the colour background (blue or green). We know that the

quality of the chroma-key and the facility with which we can obtain a desirable result is

greatly affected by this lighting ratio.

Thus, we had the option of varying the intensity of the background or that of the foreground

so as to attain a maximum overexposure of one stop or a maximum underexposure of two

stops by degrees of half a stop at a time.

In order to minimize the movement of materials and maximize the result, we opted to

modify the intensity of the foreground lighting for each shot so as to conserve the same lens

opening, maintaining the exposure of the background at the same time.

To modify the lighting, we prepared a series of neutral density filters mounted on frames

that were placed in front of the lights in accordance with the desired level of lighting. A

photometer set to incident mode was used to establish equivalent light levels from one shot

to another, and we adjusted the lens opening as needed after evaluating the image

produced on a waveform monitor. These adjustments never varied by more than one stop

from one camera to another.

C. Shooting Sequences

Sequence 1: Against a green backdrop; tungsten lighting for the foreground /

tungsten lighting for the background

Sequence 2: Against a green backdrop; daylight lighting for the foreground / daylight

lighting for the background

Sequence 3: Against a green backdrop; tungsten lighting for the foreground /

KinoFlo 525 lighting for the background

Sequence 4: Against a blue background; tungsten lighting for the foreground /

tungsten lighting for the background

Sequence 5: Against a blue background; daylight lighting for the foreground /

daylight lighting for the background

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Sequence 6: Against a blue background; tungsten lighting for the foreground /

KinoFlo 420 lighting for the background

Within each of these sequences, every camera recorded three seconds of material with

different lighting levels for the foreground (from underexposure of two stops, to

overexposure of one stop). To do this, we used a combination of neutral density filters in

front of the lights and camera lenses (1 KEY, 1 backlight, 1 ¾ back on the right) in accordance

with the desired level of underexposure or overexposure.

We produced a total of 366 shots1 of three seconds each during the course of two shooting

sessions (green backdrop and blue backdrop). Each session included three shooting

sequences (tungsten, HMI and KinoFlo lighting), during which each of the cameras (seven

video and three film) was exposed seven times.

D. Exposure and Duration of Sequences

We were looking for (and obtained) a foreground illumination level of T4 at 200 ISO so as to

get a nominal exposure of 5.6. This allowed us to obtain an overexposure of one f-stop and

an underexposure of two f-stops owing to the neutral density filters mounted on the lights.

Camera Type

Illumination

Blue Backdrop Green Backdrop

Tungsten Daylight Kino 420

Tungsten Daylight Kino 525

Kodak Vision3 5217 200T 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

Kodak Vision3 5219 500T 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

Fuji Eterna 8563 250D - 7 x 72 - - 7 x 72 -

Sony PMW-EX3 3 x 72 7 x 72 - 7 x 72 7 x 72 6 x 72

Sony SRW-9000PL 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

Panasonic AJ-HPX3700 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 5 x 72

ARRI D-21 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

RED ONE 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

1 Certain cameras did not shoot in all circumstances, as illustrated in Appendix 5.

Neutral Density

Filters

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Phantom HD Gold** 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

ARRI-Alexa 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72 7 x 72

** one sequence at 300 fps

METHODOLOGY

1. FILM PROCESSING

For the 35 mm film, the Vision Globale visual effects and postproduction house developed,

prepared and digitized the reels onto digital media. This transfer was done on an ARRISCAN-

type digitizer (2K-Log Density/DPX) at a resolution of 2K. The images were recorded on hard

discs before being sent to Technicolor for duplication and distribution.

2. DIGITAL DATA MANAGEMENT

A. Digital Format

The contents of all digital media (other than the HDCAM-SR tapes) were saved on LTO3

archive cassettes in their native format during shooting. Subsequently, the original recording

media were sent to Technicolor to be copied and transferred onto distribution hard discs.

B. File Format

Given the diversity of the acquisition formats, it was necessary to produce identical

sequences for all visual effects firms participating in the final compositing tests. Thus, the

DPX format (4:4:4 - 10 bits) was used for all the tests conducted by the visual effects houses.

The demosaicing of the raw files produced by the RED ONE camera (via the Red Rocket card)

and the Phantom HD Gold camera was done at Technicolor and DPX 10-bit sequences were

then produced.

The sequences shot on HDCAM SR were digitized using an Autodesk SMOKE workstation at

Technicolor and then converted to DPX 10-bit format.

The material recorded in Prores 422 HQ format onto KiPro hard discs (PMW-EX3 and AJ-

HPX3700 camcorders) was converted to DPX 10-bit format using a Final Cut Pro station.

C. Distribution Media

Once the sequences were converted into DPX format, 48 images of each shot were selected

and copied onto distribution hard discs furnished by the visual effects houses that

participated in the chroma-key and compositing tests.

As there was too much material to give to each of the participating visual affects houses,

Jacques Levesque produced a distribution grid, and the sequences were distributed equally

so that all parties had a mutually acceptable workload.

3. COMPOSITING

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A. Analysis Grid

The shoot executed for the purposes of this study produced a large quantity of material. The

nature of this test involved certain subjectivity in the analysis. To ensure that the results

were nevertheless significant, we needed to establish a common basis for the collection and

analysis of all these results.

It is important to remember that the fundamental objective of the project was to identify the

best exposure ratio between the foreground and background for each of the proposed

camera/colour/light combinations. To do so, a series of characteristics had to be analyzed

and the results classified so as to properly identify the best results.

We determined the following set of characteristics that the various visual effects houses had

to test and qualify:

Ease of obtaining a full key, while maintaining transparency and sharpness on contours

(matte density)

Ease of maintaining contour detail

Uniformity of light on contours

Quantity of artifacts caused by grain and noise

Accuracy of detail in angles and small enclosed spaces (holes in the grate), known as

occlusion

Quality of transparency in the fabrics and vases

Rendition of skin tones (black / white)

Preservation of tones after suppression of flare and spill

Detailed instructions were provided to the various participants, and an initial validation test

was conducted among some of them to ensure they had an adequate understanding of the

scale we had established.

Refer to APPENDIX 4 for the instructions and examples that were presented to the

participants to serve as a guide for evaluating the sequences.

B. Evaluation Scale

In order to facilitate the task of the evaluators, we proposed the following three-level

evaluation scale:

1 = Perfect

2 = Acceptable

3 = Unsatisfactory

Thus, each sequence to be evaluated was subjected to the normal chroma-key procedure,

after which the evaluator had to qualify the material in terms of the quality of the mask

produced. If a minimum of adjustment was required to arrive at a satisfactory result, a score

of 1 was assigned. However, if too much manipulation was needed to produce an acceptable

key mask, the evaluator assigned a score of 2. Finally, a score of 3 was awarded if the

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adjustment work required other tools or exceptional manipulation to achieve adequate

compositing.

We recognize that it is very rare and unusual for an experienced artist not to be able to

produce acceptable keys and composites from sequences that fall well short of the

requirements for shooting against colour backdrops. The purpose of this project was not to

see if we were able to use all the sequences shot (regardless of the quality and exposure of

the original images). Rather, the intent was to determine as of what exposure level the artist

would need to foresee employing additional exceptional measures to deliver a quality

chroma-key.

C. Software Employed

It is acknowledged that image compositing and keying is a job that requires talent and skill,

as well as an extensive knowledge of digital imagery in order to get good results. There is a

wide and diversified range of tools (software, specialized applications, etc.) available to do

this work, and they are used on different operating systems and platforms that also vary in

terms of cost and productivity.

It was impossible for us to impose one sole platform or single keying or compositing software

application on the firms that chose to participate in this project. Moreover, we had agreed

that the goal of this exercise was not to evaluate the tasks but, rather, the results.

The following software tools were employed for the evaluation of these tests:

KEYLIGHT (keyer) on NUKE (compositor) (The Foundry)

KEYLIGHT (keyer) on SHAKE (compositor) (Apple)

MASTER KEYER (keyer) on SMOKE (compositor) (Autodesk)

IBK - Image Based Keyer (keyer) on NUKE (compositor) (The Foundry)

D. Collection of Results

To offset the inherent subjectivity of the project, each sequence was tested by at least two

different artists and the results compared. After several weeks of work, the analysis tables

containing the artists’ subjective evaluations were compiled by Jacques Levesque. A certain

number of measures appeared to deviate from the results obtained elsewhere. Therefore,

we opted to counter-verify some sequences by redistributing them and validating the

results. In the majority of cases, it turned out that erroneous analysis parameters had been

used, and we were able to validate the results. However, the subjective nature of this type of

analysis had to allow for a certain variance in the results.

Several artists called for a more “subtle” evaluation scale including five instead of three

scoring levels. Nevertheless, we maintained the three-level scale because a greater number

of levels would not have enabled us to establish a clear and defined enough threshold of

acceptability for exposure levels.

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RESULTS

* THIS SECTION IS AVAILABLE ON REQUEST FOR QFTC MEMBERS ONLY

AND AT THE RATE OF $ 500 FOR NON-MEMBERS

CONCLUSIONS

* THIS SECTION IS AVAILABLE ON REQUEST FOR QFTC MEMBERS ONLY

AND AT THE RATE OF $ 500 FOR NON-MEMBERS *

22

APPENDIX 1 – PARTICIPANTS AND CONTRIBUTORS

Mel’s Cité du cinéma

MTL Vidéo

Autodesk

Centre NAD

Institut National de l’image et du Son

Le Groupe numérique

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Vision Globale

Technicolor

Alchemy 24

Boogie Studio

Digital Dimension

Oblique FX

Modus FX

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Mokko

Mr. X

Rodeo FX

Steering Committee

QFTC Representative: Christian Beauchesne Project Manager: Jacques Levesque

Production: Visual Effects:

Paul Hurteau François Lord

John Kennedy Jean-François Bachand

Daniel Vincelette, csc, DP Dominic Mercier

René Villeneuve Marcus Schioler

Sébastien Moreau

Alain Lachance

Ara Khanikian

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APPENDIX 2 – TECHNICAL CAMERA DATA

TECHNICAL CAMERA DATA

Model Sensor Resolution Sensor Size

ARRICAM /ARRI 435/ARRI 535 n/a 35 mm – 1: 1.78

24.90 mm x 18.70 mm*

Sony PMW-EX3 CMOS 1920 x 1080 ½ in 7.18 mm x 4.03 mm

Sony SRW-9000PL CCD 1920 x 1080 24.90 mm x 18.70 mm*

Panasonic AJ-HPX3700 CCD 1920 x 1080 2/3 in 9.40 mm x 5.30 mm**

ARRI D-21 CMOS 2880 x 1620 24.90 mm x 18.70 mm*

RED ONE CMOS 4520 X 2540 24.2 mm x 12.5 mm

Phantom HD Gold CMOS 1920 x 1080 25.6 mm x 25.6 mm

ARRI-Alexa CMOS 2880 x 1620 23.760 mm x 13.365 mm

* ANSI Super 35 silent camera aperture

** Typical ⅔" video camera sensor

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APPENDIX 3 – RECORDING FORMATS AND MEDIA

RECORDING FORMATS

In the table below, when more than one recording format and/or medium were used, the

format that was the subject of analysis is indicated in italics. The other formats were only

used for the purposes of content validation.

CAMERA RECORDING FORMAT (codec/rate/sampl.)

ARRI 435 Kodak Vision3 5217 200T 35 mm film digitized on ARRISCAN at 10 bits

ARRI 435 Kodak Vision3 5219 500T 35 mm film digitized on ARRISCAN at 10 bits

ARRI 435 Fuji Eterna 8563 250D 35 mm film digitized on ARRISCAN at 10 bits

Sony PMW-EX3 XDCAM-EX, HQ (1920 x 1080/23.98P) on SxS memory card in MPEG-2 4:2:0 35Mbit long GOP format

AND

1920 x 1080/23.98P ProRes HQ 4:2:2 encoded from the camcorder’s HD-SDI output on an AJA Ki-Pro recorder

Sony SRW-9000 PL

1920 x 1080 HD 4:2:2 (23.98P) Rec 709 from the camcorder’s HD-SDI output on an AJA Ki-Pro recorder

AND

1920 x 1080 S-LOG Gamma (23.98Psf) 4:4:4 RGB on HDCAM-SR tape

Panasonic AJ-HPX3700

1920 x 1080 /23.98P AVC-Intra 100 422 10-bit on P-2 memory card

AND

1920 x 1080 /23.98P Rec 709 from the camcorder’s HD-SDI output on an AJA Ki-Pro recorder

ALEXA 1920 x 1080/23.98P on SxS memory card (ProRes 444 HQ)

AND

1920 x 1080 LOG-C Gamma (23.98Psf) 4:4:4 RGB on HDCAM-SR tape

RED ONE 4K 16:9 23.98P on CF memory card (REDCODE 36)

Phantom HD Gold

1920 x 1080/23.98P in Cine 14-bit 4:4:4 format

ARRI D-21 4:4:4 RGB 1080/23.98P on an HDCAM-SRW-1 recorder

27

APPENDIX 4 – ANALYSIS PROTOCOL

1. TEST SET

The test set contained a certain number of elements that allowed us to qualitatively analyze the

ease of chroma-keying depending on exposure variations.

The set contained the following elements:

Slowly turning fan

White curtain mounted on a frame

Frosted panel

Finely perforated panel

2 vases containing orange/yellow tinted liquid

Grey and colour chip charts

Board identifying the test variables (camera, light source, exposure)

2 subjects (black man and white woman)

Large red frame delineating the sampling zone

The different exposure versions had to allow for visualizing a foreground with non-varying

luminosity and a background that illuminates/dims in accordance with the established exposure

ratio.

Slight variations of foreground lighting are possible and normal. These should in no way

influence the analysis, the exposure ratio remaining as established.

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2. NOMENCLATURE

A specific nomenclature was adopted in order to facilitate the manipulation of images and the

collection of information. The elements of this nomenclature are emulsion/camera, backdrop

colour, lighting type and exposure value.

Films:

Kodak Vision3 5213 (200T) 5213

Kodak Vision3 5219 (500T) 5219

Fuji Eterna 8563 (250D) 8563

Digital Cameras:

Sony PMW-EX3 ex3

Sony SRW-9000PL 90pl

Panasonic AJ-HPX3700 3700

ARRI D-21 d21

RED ONE red

Phantom HD Gold phd

ARRI-Alexa alex

Colours:

Blue b

Green v

Light Sources:

Kino Flo k

Daylight d

Daylight with 85 filtration df

Tungsten t

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Exposures:

Backdrop underexposed 2 stops m20

Backdrop underexposed 1.5 stops m15

Background underexposed 1 stop m10

Background underexposed .5 stop m05

No underexposure or overexposure par

Backdrop overexposed .5 stop p05

Backdrop overexposed 1 stop p10

The elements above are identified as follows:

Sensor_Colour_Light Source_Exposure

Examples:

Kodak 5213 film against blue backdrop lit by Kino with backdrop underexposed 1

stop: 5213_b_k_m10

Sony 9000PL camera against green backdrop lit by tungsten with backdrop

underexposed .5 stop: 90pl_v_ t_p05

3. ANALYSIS PARAMETERS

The shooting done as part of this study produced a large quantity of material and the nature of

this test involves certain subjectivity in the analysis. In order to ensure that the results are

nevertheless significant, we had to establish a common basis for the collection and assessment

of all these results.

The fundamental objective of the project was to identify the best balance between foreground

and background exposure for each camera/colour/light combination proposed. As such, a series

of characteristics had to be analyzed and the results classified so as to determine the best end

product.

4. SCORING

In the case of every exposure, we assigned a score of 1 to 3 for each point analyzed:

1 = Perfect — will provide excellent final results

2 = Acceptable — should be quite alright with a bit of tender loving care

3 = Unsatisfactory — I would rather not have to work on this

30

Thus, the table identifies the combination with the least amount of points as being the winning

combination. A column has also been included to allow for the identification of a preference in

the event of a tie.

It is important to remember that the goal here is not to aim for composites that reach a “final”

level. Compositors should refrain from using the various tools of the trade to get around

shooting flaws. We are looking for the combination that provides the best starting point, while

knowing full well that we have tools at our disposal that can be used to make all kinds of

improvements.

We will carefully look at the matte (alpha) generated, as well as the composite on the backdrop

provided that also served to design the lighting for the shoot. Rendering the sequences is not

essential to the analysis of all the points we wish to observe, but it certainly cannot hurt.

To help distinguish the exposures that would be more difficult to characterize, it is strongly

recommended to try composites against different solid backdrops (white, grey and black). This

variation of backdrops will help bring out specific nuances.

5. DETAILED ANALYSIS

We identified the following series of characteristics to test/qualify:

Ease of obtaining a full chroma-key while maintaining transparency and sharpness on

contours

Ease of maintaining detail on these contours

Uniformity of light on the contours

Quantity of artifacts caused by grain and noise

Accuracy of detail in angles and small enclosed spaces (holes in the grate)

Quality of transparency in the fabrics and vases

Preservation of tones after suppression of flare and spill

The procedure followed must be as standardized as possible. It is important that the backdrop

zone sampled is the same for each of the seven exposures of a series, and an average must be

determined in this zone so as to eliminate the variations caused by grain or noise. The frame

already present in the image delineates a zone, but an area that is a little more restricted can be

selected.

31

To judge each on the same basis, it is important to do a new sampling for each of the seven

exposures.

The parameters of the chroma-key software must only be minimally used. If desired, a slight

adjustment to eliminate the grey pixels of the matte between the subjects should suffice for the

principal points to be analyzed.

The analysis table includes the following aspects to evaluate:

A. Matte Density

The idea here is to compare the density of the full

portions of the matte, the density of the

transparencies, and that of the fine details on the

contours. Is the matte density proportionally

representative of the transparency value suggested by

the image, or do we lose the nuances passing abruptly

from black to white?

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B. Contour Detail

Are details readily conserved around the hair or the lace curtain? This aspect is analyzed in

parallel with density. As needed, the key can be adjusted a little to determine to what extent the

search for detail hampers matte density and vice versa.

C. Light on the Contours

Set lighting should be quite close to the backdrop

selected, and the light sources should justify the

light variations on the foreground. A bright or dark

uniform line on the contour of an element is

dubious and caused by backdrop luminosity. What

happens to contour luminosity with different

backdrop luminosities? Are certain contours too

dark or too bright for no reason?

D. Grain or Noise

Grain or noise should be evaluated on sequences of moving images. Are the fine details of hair

lost in the grain? Is it possible to get a nice transparent transition in the blurred motion of the

fan, or does the grain create too much chatter?

How do you perceive the grate and moving curtain? Does the visible noise hamper your

discernment of the motif? If the impact of grain or noise is not evident enough to judge, try

adjusting the key a little as you did for density and fine detail.

33

E. Occlusion

Similar to the details in hair, is it easy to conserve the round shapes and little angles in the

grate’s perforations? Is the matte uniform across the entire grate, or are certain sections more

degraded than others? Does the attempt to remove the matte’s grey pixels change the look of

the grate accordingly?

F. Transparencies

The transparent panel has various ranges of luminosity along with a particular texture, and it

allows the curtain to be made out behind it. Are we successful in conserving that? The vases

filled with liquid are not 100% transparent. Do we succeed in maintaining the nuances?

34

G. Suppression

Suppression serves to eliminate spill and flare caused by the colour backdrop used. As in the

case of the skin, can the colours in the set be readily conserved?

The distance used during our shoot was quite ideal and could likely make this step difficult to

assess. There is minimum spill and not much flare.

In the series of exposures tested, it is only the +1.0 version that generated questionable results,

possibly due to the flare produced by the high luminosity of the backdrop.

H. Colour Space

It is suggested to process the image in accordance with currently applied standards.

Those conducting the tests on Nuke, for example, are advised to linearize (linear to light) the

images prior to processing because this is the normal and standard process for this software. If

Autodesk software like Smoke or Flame is used, it is recommended that the processing be

carried out on the images in their original colour space, even in the case of images encoded in a

logarithmic colour space.

35

APPENDIX 5 – RESULTS TABLES

* THIS SECTION IS AVAILABLE ON REQUEST FOR QFTC MEMBERS ONLY

AND AT THE RATE OF $ 500 FOR NON-MEMBERS *

36

TEAM LIST

PRODUCTION

Producteur Christian Beauchesne Producteur John V. Kennedy Directeur de production Derek Kennedy

RÉALISATION

Réalisateur Jacques Levesque Script Fransca Waltzing Casting Cécile Barreau

ÉQUIPE EFFETS VISUELS

Superviseur VFX Jacques Levesque Équipe VFX Jean-François Ferland Christian Morin Jonathan Piché-Delorme Guylaine Dutil Ara Khanikian Philippe Désiront Alexandre Tremblay André Montambeault Laurence Berkani Benoit touchette Louis-Simon Ménard Benoit Martel Sébastien Dostie François Lord Raphaël Hubert Danny Bergeron André Geoffroy Alain Lachance Ève Brunet Yanick Wiliski

37

Marc Bourbonnais Martin Lipman Isabelle Langlois Annie Alix Sébastien Moreau

DÉPARTEMENT ARTISTIQUE

Accessoiriste de plateau Yves Fontigny

CAMÉRA

Directeur de la photographie Daniel Vincelette

Directeur de la photographie Paul Hurteau 1

e assistant à la caméra Martin Lebel

2

e assistant à la caméra Chloé Giroux-Lachance

2

e assistant à la caméra Marie-Pierre Gratton

Apprentie à la caméra Catherine Motard Apprentie à la caméra Guillaume Sabourin D.I.T. Yann Mongrain

ÉLECTRO

Chef électricien Christophe Pommiès Best boy électricien Jean-Francois Landry Éclairagiste Julien Brisebois Éclairagiste Maxime Robert-Lachaine Éclairagiste Guy Beaudet

38

GRIP

Chef grip Paul Duschesne Chef grip Christian Bergeron Best boy grip Claude Sauvageau Grip Jean-François Gingras Grip Jean-François Larivière

MAQUILLAGE/COIFFURE

Chef maquilleur Richard Bouthillier Chef maquilleur Chantal « Kim » Frenette

RÉGIE

Régisseur de plateau Stéphane Desharnais Assistante de production plateau Marie-Josée Trottier Assistante de production plateau Guillaume Dubois Cantinier Christian Marion

POST-PRODUCTION

Technicolor François Garcia Milaine Gamache Vision Globale Christophe David

CONSULTANTS

Groupe Numérique René Villeneuve

39

MTL Vidéo Paul Hurteau Nicolas Fournier Christian Navennec AQTIS Anne Mathieu