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The Great Frame Rate Debate Bruce Jacobs - Moderator Mark

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The Great Frame Rate Debate
Bruce Jacobs - Moderator
Mark Schubin
Larry Thorpe
Doug Trumbull
QG
WGBH Public Television Quality Workshop
1
Film Tradition
п‚ћ
Camera exposed 24 frames each second
п‚ћFast enough for illusion of motion
п‚ћ
Shutter normally open ВЅ the time = 1/48 second
п‚ћLonger shutter = more blur, less judder
п‚ћShorter shutter = less blur, more judder
п‚ћ
Projector shutter closes twice for each frame = 48 fps
п‚ћAvoids flicker (if projection is dim)
QG
WGBH Public Television Quality Workshop
2
US Broadcasting Tradition
п‚ћ
Camera exposed 60 fields each second
(An Interlace “field” is an inferior ½ “frame”)
Couldn’t “store” image and display twice, like film does
п‚ћOriginally the rate was the power line frequency
п‚ћAvoided flicker on early CRTs
п‚ћNoticeable flicker on later large/bright/sharp CRTs
п‚ћ
No shutter needed
п‚ћ1/60 second exposure
QG
WGBH Public Television Quality Workshop
3
US Broadcast Film Tradition
п‚ћ
Film frames are shown 3 times, 2 times, 3 times…
It’s called “3/2 pull-down”
Two film frames come out even with five video “fields”
QG
WGBH Public Television Quality Workshop
4
The New World
п‚ћ
Digital cameras can do anything
п‚ћ24, 30, 60 frames per second, and more
п‚ћWidely varying shutter speeds available
Our broadcast distribution is constrained to 60
п‚ћ Internet distribution can be anything?
п‚ћ New TVs interpolate frames!
п‚ћ
QG
WGBH Public Television Quality Workshop
5
Production Decisions
Why 24 fps?
п‚ћ Why not?
п‚ћ What do I need to know to make it work?
п‚ћ Why not 30 fps, and avoid pull-down?
п‚ћ Should I consider other frame rates?
п‚ћ What about 3D?
п‚ћ When should I use unusual shutter speeds?
п‚ћ
QG
WGBH Public Television Quality Workshop
6
The “Film Look”
Issues Related to Shooting at
Lower Picture Capture Rates
Larry Thorpe
QG
WGBH Public Television Quality Workshop
7
HD Image Acquisition
п‚ћ
Sought-for Creative “Look” encompasses:
п‚— Lighting
п‚— Focal Length
п‚— ND Filtering
п‚— Depth of Field
п‚— Aperture
п‚— Frame Rate
п‚— Shutter
п‚— Resolution
п‚— DSP Processing
24 Hz Image Capture
is a Historical Aberration…..But,
п‚ћ
24-frame motion picture film was born exclusively in the context
of movie sound
п‚ћ
This frame rate was perpetuated by the escalating constraint of
motion picture film cost escalations with increased frame rate
п‚— Failure of SMPTE 1988 agenda for 30-Frame film standard
п‚ћ
Over many decades cinematographers honed the art and
science of motion picture capture within the constraints of this
severe temporal sub-sampling
 A much-loved “Look” emerged and is globally entrenched
Motion Judder is More Visible
п‚ћ
The faster the image motion
п‚ћ
The sharper the image in motion
п‚ћ
The brighter the Scene content
п‚ћ
The brighter the viewing screen
Cinematographer “Handles” to Manage Judder
IMAGE FORMAT SIZE
ND
Filter
Optical
Low-Pass
Pre-Filter
Sample
&
Hold
Amplifier
Beam
Splitter
Lens
IR
Aperture
CCD
CMOS
Imager
ND Filter
A/D
Post
Filter
Imager
Drive Circuits
Shutter
Frame Rate
Motion of the Camera (Pan, Tilt, and Dolly)
A/D
A/D
Art of the DoP: Meticulous Control of Camera Movements
Art of the DoP: Shoot with Short Depth of Field
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