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3 Final Problems

Photography in low light

Photography in bad weather

Photo forgeries

Digital Photography with

Flash and No-Flash Image Pairs

G. Petschnigg, M. Agrawala, H. Hoppe, R. Szeliski, M.

Cohen, K. Toyama

E. Eisemann and F. Durand

Photography in Low Light

Using available

ambient light:

+ natural lighting

- high noise

- color needs

white balancing

- blur

No-flash

Adding Lighting Shows Details

Using flash:

+ details

+ color

+ low noise

- flat/artificial

- flash shadows

- red eye

Flash


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Flash + No-Flash

Combine best aspects of each image

Flash

No-flash

Result

Flash + No-Flash Approach

+ original lighting+ details/sharpness+ noise removal+ color

Result

No-flash

Use no-flash image to relight flash image

(Petschnigg), or use flash image to relight

no-flash image (Eisemann)

Acquisition Process

Lock Focus

& Aperture

1

time

Acquisition Process

1/30 s

ISO 3200

No-Flash Image

Large Sensor Gain/ISOLock Focus

& Aperture

21

time


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Recombination

Intensity

Result

Color

Flash

~* ~Result

Recombination: Intensity * Color = Original

shadow removal

Results

No-flash

Flash

Results

Result

No-flash

Flash

Poor Result

Flash

No-flash


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CVPR 2009

Photographs in Bad Weather

Haze Mist

RainFog

Images Courtesy : Steve and Carol Sheldon

Low contrast

Aerial Perspective

akaAtmospheric

Perspective

Objects farther in thedistance appear less

saturated (whiter) and less

sharp (blurrier) than those

nearby

The more atmospheric

particles between the

viewer and a distant object,

the more light is scattered


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Distant Objects are DesaturatedAerial Perspective

Leonardo, Virgin and

St. Anne, 1510

Color Perspective

Distant objects tend toward blue, near objects toward red


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Heuristic: Haze-free images have higher contrast than hazy images

Medium transmission

Most local patches in haze-free outdoor images that do not

contain sky contain some pixels that have very low intensities

in at least one color channel!


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Haze-free images have most pixels in dark

channel near 0


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Daytime, outdoor

landscapes or cityscapes

from Flickr


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Results

input recovered image

Digital Image Forensics:

Detecting Forgeries

1. Detecting photorealistic graphics

2. Detecting manipulated images

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CG vs. Real: Can You Do It?

fakeorfoto.com

I got 5 out of 12 right

Chance = 6 out of 12

Digital Image Forensics:

Detecting Forgeries

http://www.life.com/archive/realfake

I got 6/10

Chance = 5/10

Detecting Forgery -- Why It Matters: Trust

Iconic Portrait of Lincoln (1860)Lincolns head on John Calhouns body

Examples collected by Hany Farid: http://www.cs.dartmouth.edu/farid/research/tampering.html

1989 composite of Oprah and Ann-Margret (without eithers permission)

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http://area.autodesk.com/fakeorfoto/http://www.life.com/archive/realfakehttp://www.cs.dartmouth.edu/farid/research/tampering.htmlhttp://www.cs.dartmouth.edu/farid/research/tampering.htmlhttp://www.life.com/archive/realfakehttp://area.autodesk.com/fakeorfoto/


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2008

1930s: Stalin had disgraced comrades airbrushed out of his

pictures

http://www.cs.dartmouth.edu/farid/research/digitaltampering/

http://www.newseum.org/berlinwall/commissar_vanishes/index.htm

2000: black students face inserted into UW magazine

http://www.cs.dartmouth.edu/farid/research/digitaltampering/

Pulitzer Prize winning photograph of Kent State killing (1970)

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http://www.cs.dartmouth.edu/farid/research/digitaltampering/http://www.newseum.org/berlinwall/commissar_vanishes/index.htmhttp://www.newseum.org/berlinwall/commissar_vanishes/index.htmhttp://www.cs.dartmouth.edu/farid/research/digitaltampering/http://www.cs.dartmouth.edu/farid/research/digitaltampering/http://www.newseum.org/berlinwall/commissar_vanishes/index.htmhttp://www.newseum.org/berlinwall/commissar_vanishes/index.htmhttp://www.cs.dartmouth.edu/farid/research/digitaltampering/


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2003: Long-time staff photographer for LA Times was fired for this one

Published photo

Kerry at Rally for Peace 1971 Fonda at rally in 1972

Caption: Actress and Anti-war

activist Jane Fonda speaks to a

crowd of Vietnam veterans, as

activist and former Vietnam vet John

Kerry listens and prepares to speak

next concerning the war in

Vietnam. (AP Photo)

Detecting Forgery: Cloning

Exposing Digital Forgeries by Detecting Duplicated

Image Regions

A.C. Popescu and H. Farid

Technical Report, TR2004-515, Dartmouth College, Computer

Science

Detecting Forgery: Retouching

Exposing Digital Forgeries in Color Filter Array

Interpolated Images

A.C. Popescu and H. Farid

IEEE Transactions on Signal Processing, 53(10):3948-3959,

2005

2005: Pres Bush scribbles a note to C. Rice

during UN Security Council Meeting

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Demosaicing Prediction

In demosaicing, RGB values are filled in based on

surrounding measured values

Filled in values will be correlated in a particular way for

each camera Local tampering will destroy these correlations

Farid: Photo Fakery

and Forensics 2009

Detecting Forgery: Lighting/Shadows

Exposing Digital Forgeries by Detecting

Inconsistencies in Lighting

M.K. Johnson and H. Farid

ACM Multimedia and Security Workshop, New York, NY, 2005


Exposing Digital Forgeries by Detecting

Inconsistencies in Lighting

M.K. Johnson and H. Farid

ACM Multimedia and Security Workshop, New York, NY, 2005

Estimating Lighting Direction

1 Method: 2D direction from occluding contour

Provide at least 3 points on occluding contour (surface

has 0 angle in Z direction)

Estimate light direction from brightness

Estimate

Ground

Truth

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Detecting Inconsistencies in Lighting

Fake photo

Real photo


Lighting: Specular Highlights in the Eye

M.K. Johnson and H. Farid, Exposing Digital Forgeries Through Specular

Highlights on the Eye,2007

Estimating Lighting from Eyes

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http://www.cs.dartmouth.edu/farid/publications/ih07.htmlhttp://www.cs.dartmouth.edu/farid/publications/ih07.htmlhttp://www.cs.dartmouth.edu/farid/publications/ih07.htmlhttp://www.cs.dartmouth.edu/farid/publications/ih07.html


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Summary

Digital forgeries are an increasingly major

problem as it becomes easier to fake images

A variety of automatic and semi-automatic

methods are available for detection of well-done

forgeries

Checking lighting consistency

Checking demosaicking consistency (for high quality

images)

Checking JPEG compression level consistency (for

low quality images)

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Documents