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Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 [email protected] 1

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Page 1: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Computer Science E-7Exposing Digital Photography

Lecture 6: The HistogramOctober 19, 2009

[email protected]

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Page 2: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms General Histogram

Image from http://en.wikipedia.org/wiki/Histogram

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Page 3: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Digital Photography

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Black WhiteSome

Many

Page 4: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Total Underexposure

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Page 5: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Total Overexposure

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Page 6: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Well-exposed samples

Photo by Dan Armendariz, 2009309s, ISO 100

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Page 7: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Well-exposed samples

Photo by Dan Armendariz, 20071/1000s, ISO 400, f/5.6

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Page 8: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Well-exposed samples

Photo by Dan Armendariz, 2007

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Page 9: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms

Under-exposure

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Photo by Dan Armendariz, 2005

8.0s, ISO 100, f/8

Page 10: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms

Over-exposure

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Photo by Dan Armendariz, 2005

15.0s, ISO 100, f/16

Page 11: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Exposure Compensation

Photos by Dan Armendariz, 2005Left: 1/80s, ISO 400, f/2.8, 0ev. Right: 1/80s, ISO 800, f/2.5, +1.3ev

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Page 12: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Over- & Under-exposure

Photo by Dan Armendariz, 20061/80s, ISO 400, f/10

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Page 13: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Bits and Bytes Refresher

Bit 0 or 1

Byte 8 bits

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Page 14: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Bits and Bytes As related to histograms

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Black White0 255

Page 15: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Bits and Bytes Bit Depth

JPEG

Red Green Blue

8-bit 8-bit 8-bit

0 255 0 255 0 255

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Page 16: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms What about color?

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Red Green Blue

?

Page 17: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

The Eye Luminance Detection

Image from http://en.wikipedia.org/wiki/Trichromacy

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Page 18: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

The Eye Luminance Detection

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Red Green Blue

Page 19: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Luminance Calculation

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Luminance ≈ 0.3 R + 0.59 G + 0.11 B

Page 20: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Luminosity Histograms DIY!

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Page 21: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Luminosity Histograms DIY!

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Page 22: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Luminosity Histograms DIY!

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Page 23: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms More than just Luminosity...

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Lum

R

B

G

Page 24: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Luminosity, Colors, & RGB

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Lum

Colors

RGB

Page 25: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Luminosity, Colors, & RGB

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Images from http://www.cambridgeincolour.com/tutorials/histograms2.htm

Page 26: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms Luminosity, Colors, & RGB

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Images from http://www.cambridgeincolour.com/tutorials/histograms2.htm

Page 27: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Histograms What is Black and White?

Photo by Dan Armendariz, 20061/80s, ISO 400, f/10

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Page 28: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Dynamic Range The Eye

Image from http://en.wikipedia.org/wiki/Fovea

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Page 29: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Dynamic Range Digital Cameras

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Pixel (“Bucket”)

Photons (Light)

Collected Light

Page 30: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Dynamic Range Simplified Calculation

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Dynamic Range =Biggest Signal (full “bucket”)Smallest detectable signal

Page 31: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Dynamic Range In Scenes

Photo by Dan Armendariz, 20061/80s, ISO 400, f/10

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Page 32: Computer Science E-7 Exposing Digital Photography · Computer Science E-7 Exposing Digital Photography Lecture 6: The Histogram October 19, 2009 danallan@mit.edu 32. Created Date:

Computer Science E-7Exposing Digital Photography

Lecture 6: The HistogramOctober 19, 2009

[email protected]

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