This document discusses several key digital imaging fundamentals in Photoshop, including benefits of higher megapixel counts such as more detail and ability to digitally zoom, pixel aspect ratios, anti-aliasing techniques, primary colors in RGB and CMYK systems, color and alpha channels, grayscale vs bitmap modes, understanding Lab color and histograms.
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Chapter03
1. Ch 3: Digital Imaging Fundamentals
Photoshop CS6 Essentials
By Scott Onstott
2. Ch 3: Digital Imaging Fundamentals
Benefits of More Megapixels
• Larger DSLR sensors capture millions
more pixels (megapixels) compared to
point-and-shoot cameras
• More megapixels means you have
more detail and less noise
• You can digitally zoom in to large
images and the details remain crisp
• More megapixels also means more
data, larger file sizes, and more RAM
required
3. Ch 3: Digital Imaging Fundamentals
Pixel Aspect Ratio
• Pixels can have non-square aspect
ratios
• Use square pixels for print and for the
Web
• Video clips often use non-square
pixels
• You can change the pixel aspect ratio
using the View menu and in the File >
New dialog box
4. Ch 3: Digital Imaging Fundamentals
Aliasing and Anti-Aliasing
• Aliasing is the stair-stepping artifact
that occurs in grids of pixels
• Lines are not aliased when you draw
them horizontally, vertically, or at 45
degree angles
• Off-angled lines exhibit aliasing which
can be reduced by dithering the edge
(blue line at right) with intermediate
values
• Anti-aliased edges appear blurry
compared to aliased edges but the
stair-stepping is removed
5. Ch 3: Digital Imaging Fundamentals
Primary Colors
• Red, Green, and Blue are the primary
additive colors
• Cyan, Magenta, and Yellow are the
primaries of subtractive colors
• CMY are secondary colors in the RGB
system
• RGB are secondary colors in the CMY
system
• Black (abbreviated as K) is added to the
subtractive system, making CMYK the 4-
colors used in offset printing
10. Ch 3: Digital Imaging Fundamentals
Understanding Histograms
• Histograms help you see how well the
dynamic range is being utilized
• Histograms are made of black vertical bars
representing how many pixels are in the
shadows, mid-tones, and highlights
• Blank areas at the edges of a histogram show
there are values (blackest blacks or whitest
whites) that aren’t being used
• Gaps or spikes in a histogram show that
information has been “destroyed” by being
pushed beyond certain mathematical limits