Seeing, Adapting to, and Reproducing the Appearance of Nature

Seeing,
Adapting to, and
Reproducing the
Appearance of Nature
Mark D. Fairchild
Rochester Institute of Technology
College of Science
Munsell Color Science Laboratory
The HDR
Photographic Survey
Not THAT HDR ....
Objectives
Online High-Dynamic Range Image Database
Calibrated Images
Colorimetric Scene Measurements
In Situ Color Appearance Scaling
Pleasant Scenes (Psychophysics)
Technical Challenges (Rendering)
40 Scenes ...
Inspiration
19th Century Photographic Surveys of the American West
William Henry Jackson, Mt. of the Holy Cross
www.cis.rit.edu/fairchild/HDR.html
Procedures
Calibrated/Characterized Nikon D2x
9 Exposures, 1-Stop Increments (typical)
Assembly into Linear HDR Image (CS2)
OpenEXR, 32-Bit Floating Point
Scene Colorimetry, Appearance, Other Data
Mirror Ball Image
All Details Online
OpenEXR
<www.openexr.com>
OpenEXR is a high dynamic-range (HDR) image file format developed by Industrial
Light & Magic for use in computer imaging applications.
OpenEXR is used by ILM on all motion pictures currently in production. The first
movies to employ OpenEXR were Harry Potter and the Sorcerers Stone, Men in Black
II, Gangs of New York, and Signs. Since then, OpenEXR has become ILM's main
image file format.
OpenEXR's features include:
• Higher dynamic range and color precision than existing 8- and 10-bit image file
formats.
• Support for 16-bit floating-point, 32-bit floating-point, and 32-bit integer pixels.
The 16-bit floating-point format, called "half", is compatible with the half data
type in NVIDIA's Cg graphics language and is supported natively on their new
GeForce FX and Quadro FX 3D graphics solutions.
• Multiple lossless image compression algorithms. Some of the included codecs
can achieve 2:1 lossless compression ratios on images with film grain.
• Extensibility. New compression codecs and image types can easily be added by
extending the C++ classes included in the OpenEXR software distribution. New
image attributes (strings, vectors, integers, etc.) can be added to OpenEXR
image headers without affecting backward compatibility with existing OpenEXR
applications.
Measurement Map
5
6
4
1
3
2
Camera Characterization
Nikon D2x
Linear HDR Image Data
12-Bit RAW --> 16-Bit TIFF --> 32-Bit OpenEXR
3x3 Matrix from Linear RGB to CIE XYZ
Verified in a Second Research Project
Mean ΔEab = 2.5 (Max = 5.5)
Example Data Sheet
Some Applications
HDR Rendering Algorithms (Tone Mapping)
Image Appearance Models (e.g, iCAM)
Psychophysics
HDR & Extended Gamut Displays
Camera Metering Patterns
Image Rendering (Lighting)
...
...
...
Examples
9-Stop Mosaic
Linear OpenEXR
Locally Rendered
9-Stop Mosaic
Linear OpenEXR
Locally Rendered
Rendering Comparison
Linear
CS2 Local
iCAM06
Comparison 2
Linear
CS2 Local
iCAM06
Mirror Balls
Website
<www.cis.rit.edu/fairchild/HDR.html>
Image
Appearance
Modeling
iCAM06 Framework
+
Details
Adjustment
-
Details-layer
400
Independent Gain Control
350
Photoreceptor Responses
1.00
0.90
Relative Response
0.80
0.70
0.60
0.50
0.40
0.30
0.20
XYZ
Base-layer
250
200
150
100
50
0.10
RGB Input
300
−1
0.00
chromatic adaptation
390
440
490
540
590
640
690
Wavelength (nm)
0
−2
−1
0
1
0
1
1
2
3
3
5
4
5
6
7
8
Log(I)
tone-compression
Tone-compressed
“White”
Inverse
Output Model
RGB Output
Inverse CAT
IPT Uniform Color Space
Surround Adjustment
Colorfulne
ss
Bilateral Filter - Blur, but preserve large, edge transition
Subtract filtered base layer from original to get detail layer
Adapt base layer with blurred image (iCAM)
Recombine with detail layer
Detail-combined
+
+
Chromatic Adaptation
A Cyan Filter
Adaption: Color
Adaption: Blur (Sharpness)
To See and To See ...
Rafael Gomez Valverde, To Look and To Look
To See and To See ...
Rendering Choices
Device Characterization
Perceptual Modeling
Who Does This?
What Do Your Images Really Mean?
Light & Color In Nature
Light can be measured physically.
Color is a human perception...
Thank You ...
Thank You ...
Thank You ...