Production Technologies

1
Production Technologies

• The Central Role of the Lens in
• HDTV Imaging

Laurence J. Thorpe Broadcast Communications Cano
n U.S.A.
2
Broadcast Transmission Systems

• Signal Integrity
• Quality of Service
• Channel capacity
• Transmission Impairments
• Noise
• Interference
• Fading
• Ghosts
• Reflections
• Bit Error Rates

3
The HDTV Lens as Transmission System

• Optical Image Integrity
• Quality of Service namely, Quality of Image
• Channel capacity namely, Sensitivity
• Transmission Impairments
• Fundamental Optical Limitations
• Distortions
• Aberrations
• Ghosts
• Reflections

4
HDTV Lens as Transmission System
5
HDTV Production

• Creative Role
• of the
• HD Lens

6
Role of the HDTV Lens
Lighting
Scene
Digital Camera
Lens
Represent In digital domain
Capture on Digital Media
Create The Optical Image
Digital Recorder
Image is completely defined at this point
7
Creation of the Optical ImageMultidimensional
Aspect of the Optical Image

• Shaping the Image
• Angle of View
• Framing of a chosen image segment from object
  scene
• Zoom
• Real-time dynamic adjustment to Angle of View
• Depth of Field
• Expressing a 3-D representation on a 2-D image
• Perspective
• Further creative adjustment to sense of picture
  depth

8
Creation of Optical ImageMultidimensional Aspect
of the Optical Image

• Qualifying the Picture
• Contrast
• Tonal Reproduction
• Color Reproduction
• Lens Transmittance Characteristic
• Picture Sharpness
• Resolution what is this in the context of
  distant viewing ?

9
Quality Optics for HDTV

• The
• Lens-Camera
• Imaging System

10
Role of the Digital Camera
Optical Representation Of the Object Scene
Digital Modification
Digital Representation According to ITU 709
RGB Digital Processing Facilitates adjustments
to meet the prescribed HDTV Production Standard
Opto-Digital Transformation
RGB Digital
Imaging System
Digital Representation Of the Optical Image

• Detent Settings
• ITU 709 High Def Standard

11
Role of the Digital Camera
Optical Representation Of the Object Scene
Digital Modification
Digital Representation According
to Creative Aesthetic Desires

• RGB Digital Processing
• Facilitates adjustments to
• Tonal Reproduction
• (Gamma and Knee)
• Color Reproduction
• (Colorimetry)
• Picture Sharpness
• (Image Enhancement)

Opto-Digital Transformation
RGB Digital
Imaging System

• Adjustable Settings
• Creative Control

Digital Representation Of the Optical Image
12
The Science of Optical Design

• Is a Science of Optimization
• Dealing with Multiple Variables
• Multiple Picture Attributes
• Multiple Aberrations
• These Parameters are Dynamic in that they vary
  with
• Zoom
• Focus
• Iris

13
HDTV Studio Zoom Lens
14
HDTV Studio Zoom Lens
Variator
Compensator
15
HDTV Zoom Lens
Wide Angle
Mid Zoom Range
Telephoto
16
The Science of Optical Design

• Multiple Attributes
• Contributing to
• Overall
• Image Performance

17
Image Performance Parameters

• Sensitivity
• The inherent Optical Speed of the lens (the
  channel capacity)
• Picture Contrast
• Tonal Reproduction (integrity of the grey scale)
• Reproduction of Dark portions of the scene
• Handling of strong light sources
• Color Reproduction
• Color Gamut
• Picture Sharpness
• Horizontal and Vertical Resolution
• Limiting Resolution
• Resolving Power

18
The Science of Optical Design

• Multiple Impairments
• Attempting to Detract
• from Overall
• Image Performance

19
Lens Aberrations

• For a single Lens Element
• There are FIVE aberrations
• for monochromatic light
• Mathematically predicted by
• a German scientist Seidel
• in 1856

20
Five Aberrations of Seidel

• Spherical Aberration
• Parallel light at lens edge converges to focal
  point nearer to lens than
  light passing through center
• Coma
• Comatic aberration is a phenomena visible in the
  periphery
  of an image light rays entering the edge of the
  lens at an angle
  converge in the form of a comet
• Astigmatism
• Off-axis subject point appears as an ellipse
• Curvature of Field
• Focusing on a flat object field produces a
  bowl-shaped optical image
• Distortion
• Geometric distortions of the pincushion and
  barrel form

21
Optical Limitations Aberrations

• Optical Physical Limitations
• Diffraction imposes a fundamental limitation to
  MTF
• Relative Light Distribution Light fall-off from
  picture center
• Focus Breathing Angle of view changes with
  focus control
• Distortions Aberrations
• Spherical
• Curvature of Field
• Coma
• Astigmatism
• Geometric
• Chromatic Aberrations (Lateral and
  Longitudinal)
• Flare, Ghosting, and Veiling Glare
• Unwanted stray rays stimulated by highlights

Focusing Distortions
22
Quality Optics Optimizing Multiple Variables
Increasing Costs
Perfect Lens

• Total Lens
• Performance
• Maximum Attributes
• Minimum Impairments

HDTV Lens
SDTV Lens

• Collective Technology Refinements
• Collective Manufacturing Processes

23
HDTV Lens-Camera Resolution

• Concept
• Of
• Modulation Transfer Function
• (MTF)

24
Modulation Transfer Function (MTF)

• The Contrast of these Spatial Frequencies
• Diminishes as the frequency increases
• The Behavior of that Contrast with Frequency
• Described by the Modulation Transfer Function

25
Image Resolutionas Described by MTF
Characteristic
100
Modulation Transfer Function (MTF)
MTF
Lens Contrast
Limiting Resolution
Lens Resolving Power
Video TVL / ph Optical LP / mm

26
Concatenation of MTF(Provides System MTF)
Human Visual System
Camera Sampling
Display
Lens
MTF 1 X MTF 2 X MTF 3 X MTF 4
27
Typical 1920 (H) x 1080(V) HD Camera and Lens
872 TVL/ph
SMPTE Specified Filter
Carrier
30 MHz
100
Lens
Horiz MTF
50
45
HD Camera
2160
1080
Horizontal
800 Ref Measurement
TVL/ph
Nyquist Limit
28
HDTV Resolution

• Picture
• Sharpness

29
Picture Sharpness

• Visual Picture Sharpness
• Is
• Proportional to the
• Square of the Area under the MTF Curve
• Otto Schade Snr
• RCA Research Labs

30
Picture Sharpness
100
Modulation Transfer Function (MTF)
Contrast Level
2
MTF
Limiting Resolution
Video TVL / ph Optical LP / mm

Spatial Frequency
31
Image Resolution
100
Most important region of the MTF curve
Picture Sharpness
Least important region
Contrast Level
Image Texture
Resolving Power
Picture Definition TVL/ph
Line Pairs/mm

32
The Importance of In-Band MTF
872 TVL/ph
100
30 MHz
Carrier
Lens-Camera Typical Spec
Horiz MTF
50
2160
1080
TVL/ph
Horizontal
800 Ref Measurement
200 400 600
Nyquist Limit
33
The Importance of In-Band MTF
872 TVL/ph
100
30 MHz
Carrier
Lens-Camera Typical Spec
Horiz MTF
50
Unspecified but Vitally important To Picture
Sharpness
1920
800 Ref Measurement
1080
TVL/ph
Horizontal
200 400 600
Nyquist Limit
Fs
34
The Studio LensOptimization of Picture Sharpness
High MTF Across Image Plane

• Minimum
• Defocusing
• Distortions

• High Contrast
• Flat
• Relative
• Illumination

35
Relative MTF of HDTV and SDTV 2/3-Inch Studio
Lens Measured at Picture Center Wide-angle _at_
F-4.0
169 5.5 MHz SDTV Band-edge
100
SDTV
MTF
LP/mm Line-Pairs per Millimeter
20 40 60 80
36
Relative MTF of HDTV and SDTV 2/3-Inch Studio
Lens Measured at Picture Center Wide-angle _at_
F-4.0
169 5.5 MHz SDTV Band-edge
100
Bandpass Of Interest
SDTV
MTF
LP/mm Line-Pairs per Millimeter
20 40 60 80
37
MTF of 2/3-Inch HDTV Studio Lens Measured at
Picture Center Wide-angle _at_ F-4.0
100
HDTV
MTF
20 40 60 80
LP/mm
38
MTF of 2/3-Inch HDTV Studio Lens Measured at
Picture Center Wide-angle _at_ F-4.0
1080/60i HDTV Band-edge
100
HDTV
MTF
20 40 60 80
LP/mm
39
Relative MTF of HDTV and SDTV 2/3-Inch Studio
Lens Measured at Picture Center Wide-angle _at_
F-4.0
169 5.5 MHz SDTV Band-edge
1080/60i HDTV Band-edge
100
HDTV
Bandpass Of Interest
Bandpass Of Interest
X 2.7
MTF
SDTV
LP/mm Line-Pairs per Millimeter
20 40 60 80
40
MTF of 2/3-Inch HDTV Studio Lens Measured at
Picture Center Wide-angle _at_ F-4.0
Optical Reference
Camera Reference
1080/60i HDTV Band-edge
100
HDTV
MTF
56 LP/mm
20 40 60 80
74 LP/mm
LP/mm
41
MTF of 2/3-Inch HDTV Studio Lens Measured at
Picture Center Wide-angle _at_ F-4.0
Optical Reference
720P Camera Reference
720/60P HDTV Band-edge
100
HDTV
MTF
56 LP/mm
20 40 60 80
49 LP/mm
LP/mm
42
Relative MTF of HDTV and SDTV 2/3-Inch Studio
Lens Measured at Picture Center Wide-angle _at_
F-4.0
169 5.5 MHz SDTV Band-edge
1080/60i HDTV Band-edge
Optical Reference
100
HDTV
SDTV
MTF
56
LP/mm Line-Pairs per Millimeter
20 40 60 80
43
Picture Sharpness and MTF

• MTF is Dynamic
• Across the
• Image Plane

44
169 HD Lens MTF Measurements
7.0 mm
5.4 mm
Corner
Middle
2.0 mm
3.9 mm
Center
9.6 mm
3.5 mm
45
Lens MTF across Image Plane(Measured at 56 Lp/mm
or 600 TVL/ph _at_ f-4.0)
100
90
80
70
MTF
Center Middle Corner
46
Lens MTF across Image PlaneMeasured at 56 Lp/mm
(or 600 TVL/ph) _at_ F-4.0
100
90
HDTV
80
70
SDTV
MTF
Center Middle
Corner
47
Picture Sharpness and MTF

• MTF
• Varies with
• Focal Length

48
Variation of MTF with ZoomMeasured at Picture
Center 56 Lp/mm _at_ F-4.0
100
90
HDTV
80
70
MTF
SDTV
Focal Length in mm
Wide 15 30 45 60
90 120 Tele

49
MTF Profile with Focal Length(Measured at 56
Lp/mm)
100
90
Mid-range
80
Telephoto
70
Wide-angle
MTF
Center Middle
Corner
50
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51
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52
Picture Sharpness and MTF

• MTF
• Varies with
• Object Distance

53
Variation of MTF with Object DistanceMeasured at
Picture Center at 56 Lp/mm _at_ F-4.0
100
HDTV
90
80
70
MTF
SDTV
Object Distance in Meters
0.6 1.0 2.0 3.0 5.0 10.0 50.0
Infinity
54
Picture Sharpness and MTF

• MTF
• Is Dynamic
• With
• Aperture Setting

55
MTF as a Function of Aperture The Perfect Lens
(Diffraction Limited)
30MHz 872 TVL/ph
HDTV Passband
Optical Reference
HD Reference 27.5MHz 800 TVL/ph
100
F 2.0 F 4.0 F 8.0 F 16.0
Modulation Transfer Function (MTF)
SDTV 400 TVL/ph
20 40 60 80
Lp/mm
74 Lp/mm 800TVL/ph
56 Lp/mm 600 TVL/ph
30 Lp/mm
TVL/ph
(1080-Line System)
56
MTF Profile with Focal Length(Measured at 56
Lp/mm)
Iris Wide Open
100
90
80
Wide-angle
70
Mid-range
Telephoto
MTF
Center Middle
Corner
57
MTF Profile with Focal Length(Measured at 56
Lp/mm)
100
Aperture F- 4.0
90
Mid-range
80
Telephoto
70
Wide-angle
MTF
Center Middle
Corner
58
HDTV Lens

• Light Management
• Within the
• Lens Transmission System

59
Light Management

• Spectral Transmittance
• Sensitivity
• Color Reproduction
• Relative Light Distribution
• Chromatic Aberrations
• Lateral
• Longitudinal

60
HDTV Lens

• Spectral
• Transmission

61
Lens Spectral Transmittance
62
Lens Spectral Transmittance
63
Spectral Transmittance

• Lens
• Color Reproduction

64
HDTV Color Reproduction
Sample Hold Amplifier
CCD Imager
Lens
Digital Processing
Beam Splitter
A/D
Lens Prism Imager
Spectral Spectral
Spectral Linear
Matrix Transmittance Shaping
Response
X
X
X
65
Studio Tungsten 3200 degree
IR Cut Filter


Generic Camera Prism
CCD Imager
66
Many Variables relating to Color Reproduction

• CAMERA PRISM IMAGER
  LENS
• Canon Fujinon Matsushita
  Sony Toshiba Angenieux Canon Fujinon
• Hitachi
• Ikegami
• Panasonic
• Sony
• Thomson

67
Testing the HDTV Lens

• Relative Light Distribution

68
Specification of Light Distribution
Image Height
5.5mm
2.7mm
5.4 mm
4.8mm
9.6 mm
69
Lens Relative Light Distribution

• The Lens F-Number
• Indicates the Amount of Light collected at the
  Center of the Image
• Natural Vignetting
• Off-axis Points do not receive this same Amount
  of Light
• Cosine 4th Power Law light reaching the image
  margins decreases
• as the 4th power of the Cosine of angle of
  view
• Optical Vignetting
• Oblique light rays are presented with a lesser
  lens opening than on-axis rays
• Mechanical or Hard Vignetting
• Caused by extensions added to the lens lens
  hoods, matte box holders etc

70
Lens Light Distribution
71
Lens Light Distribution