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ACM202
what is a digital photograph?
Session 1, 2013
Alison Bennett
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The dematerialisation of the photograph
for the first time in history
the image is a dynamic system.
- Rush, M 2005, New Media in Art, Thames & Hudson, London, UK, p. 181
The photograph is no longer a
physical object but a collection ofnumbers translated at recall
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WHAT IS A DIGITAL IMAGE?
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A digital image is
a grid of pixels
With the technology back then,you had very limited palette in
which you were able to draw a
character. If you look at the
original Mario face, you had just 7
pixels to draw his face. My goal
within that limited palette was to
create a character that was as
distinct as possible. Because of
that, he had some of his now-
distinct features such as his big
nose.
Read more: Exclusive Interview
With Nintendo GamingMastermind Shigeru Miyamoto -
Popular Mechanics 18 December
2009
http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/4334387http://www.popularmechanics.com/technology/gadgets/video-games/43343877/27/2019 Week one lecture notes
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A digital photograph is a fine grid of pixels
giving the illusion of continuous tone
12x16 pixels 800x900 pixels
http://epicrapbattlesofhistory.wikia.com/wiki/File:ERB_Mario_Bros.png
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pixel is short of picture element
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A picture made of
elements is not a new
idea: eg Mosaic
Mosaic portrait of a lady, PompeiiMuseo di Capodimonte
7
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Computers are basically
binary switch machines:
on or off; 1 or 0A fax or a photocopy: black or white
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Bits & pieces
BIT is short for Binary Digit: 1 or 0 (On or Off)
Bit Depth refers to how much tonal range is
available for each pixel.
A 1-Bit image is just black and white, like a
photocopy no grey.
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8 bit RGB vs bitmap
8 bit RGB bitmap
10
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The challenge of digital photograhy
To create the illusion
of continuous tone
vs. posterisation
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The illusion of continuous tone
Graduated tonal range VS Posterisation
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Levels of tone
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Levels per bit
Bit Depth Colours Available: 1-bit: black and white / on or off / 1 or 0
2-bit: 4 levels of tone per channel
4-bit: 16 levels of tone per channel
8-bit: 256 levels of tone per channel 16-bit: 32,768 levels of tone per channel
24-bit: 16.7 million levels of tone per channel
Each step in bit depth doubles the number oflevels of tone available within that colourchannel.Eg. 7-Bit = 128 levels
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Remember our challenge: Continuous tone
Human perception
requires at least 200
levels, steps in tone, to
create the illusion of
continuous tone
Therefore 8bit is the
most efficient bit depth
7bit=128 levels;
8bit=256 levels
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8bit: 256 levels of tone
16
White: 255Black: 0
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Material to virtual
How do we get from
continuous tone, as weperceive it in the world,
to digital photographicrepresentation?
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What goes on inside the camera?
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The sensor
The sensor is either
a CCD charged
coupled device or
a CMOS'Complementary
Metal-Oxide
Semiconductor'.
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2009: Nobel
prize for Physics
In 1969 Willard S. Boyleand George E. Smithinvented the firstsuccessful imagingtechnology using a digitalsensor, a CCD (Charge-Coupled Device).
The CCD technology makes use of thephotoelectric effect, as theorized by AlbertEinstein and for which he was awarded the 1921years Nobel Prize. By this effect, light istransformed into electric signals. The challengewhen designing an image sensor was to gatherand read out the signals in a large number ofimage points, pixels, in a short time. The CCD isthe digital cameras electronic eye. Itrevolutionized photography, as light could nowbe captured electronically instead of on film. Thedigital form facilitates the processing and
distribution of these images.
http://nobelprize.org/nobel_prizes/physics/laureates/2009/info.pdf
http://www.npr.org/templates/story/story.php?storyId=113527362
http://nobelprize.org/nobel_prizes/physics/laureates/2009/info.pdfhttp://nobelprize.org/nobel_prizes/physics/laureates/2009/info.pdfhttp://nobelprize.org/nobel_prizes/physics/laureates/2009/info.pdfhttp://www.npr.org/templates/story/story.php?storyId=113527362http://www.npr.org/templates/story/story.php?storyId=113527362http://www.npr.org/templates/story/story.php?storyId=113527362http://www.npr.org/templates/story/story.php?storyId=113527362http://nobelprize.org/nobel_prizes/physics/laureates/2009/info.pdfhttp://nobelprize.org/nobel_prizes/physics/laureates/2009/info.pdf7/27/2019 Week one lecture notes
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Sensor & the Bayer Array
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Online video: pixel colour
http://www.youtube.com/watch?v=2-stCNB8jT87/27/2019 Week one lecture notes
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The difference between what you see and
what the camera sees
How you see an image How your camera sees the image
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eye more sensitive to mid tones
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What is light?
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Mid tones within the green band
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Additive RGB colour mixing
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White is all colours combined
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Colour film was made up of 3 layers
recording a tonal image of that colour
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Digital colour works much the same way
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Photoshop channels of RBG:
B&W channels determine the intensity
of primary colour for that sub-pixel
Notice that
the channels
are B&W?
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Getting in close: sub pixels
Have you got up close to the bigscreen in Fed Square?
33
RBG Channels:
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RBG Channels:grey scale of colour intensity: 0-255
a filter of how much of that colour channel to let
through
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RGB Colour: note B&W filters in Channels256 levels of Red x 256 levels of Green x 256 Levels of Blue =
almost 17 million possible colours
RED
R: 255
G: 0B: 0
GREEN
R: 0
G: 255B: 0
BLUE
R: 0
G: 0B: 255
Magent
a
R: 255
G: 0
B: 255
Cyan
R: 0
G: 255
B: 255
Yellow
R: 255
B: 0
G: 255
Channels
like B&W
filters
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FYI:
Seth Lambert
RGB Numbers of a 2 DPI Self-Portrait2005
320 individual sets of numbers
indicating the Adobe Photoshop color
values of the pixels of a 2 DPI
photograph of myself. The number
sets are selections from screenshots of
the Photoshop file. The original pixel
grid that makes up the digital
photograph is maintained in my final
grid of numbers. 1 pixel number set is
equal to 1 inch.
http://www.sethlambert.net/failures7.
php
http://www.sethlambert.net/failures7.phphttp://www.sethlambert.net/failures7.phphttp://www.sethlambert.net/failures7.phphttp://www.sethlambert.net/failures7.php