UNITS OF MEASUREMENT
2.01 Understand Digital Raster Graphics
What Unit of Measurement to Use
Quiz Question: List as many units of measurement that
you can think of as a class.
Did you have more than one from the list below?
•
•
Inches
Pixels
•
•
Points
Picas
We generally pick what we are comfortable with, but
in Graphic Design it should be based on need.
Inches
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The standard unit of measurement for the United
States and U.S. standard sized papers.
What is 8.5” x 11” called? 11” x 14”? 11” x 17”?
 Letter,

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Legal, and Tabloid
Letter size is standard for most printers, resumes,
and other common documents.
Works well when defining document sizes for print.
What most of us are comfortable with.
Pixels


The most common unit of measurement for computer
screen display.
Generally represented by one dot that is
illuminated on a computer screen.
 Many


pixels make up an image or images.
A precise measurement system for web-design.
Lacks flexibility as screen sizes change.
Points



The standard unit of measurement for typefaces.
1 point represents 1/72 of an inch.
Therefore text formatted with a font size of 72 pt is
about one inch.


However, variations occur due to font designs.
Standard size for print paragraphs = 12 pt (Generally)
Picas

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Quiz time: What is 11 inches divided by 3?
Quiz time, part two: What is 72 divided by 3?
One pica equals 1/6 of an inch. Six picas per inch.
Often used in print design, since it is easily divisible.
Picas work well when applying the Rule of Thirds.
IMAGE RESOLUTION
AND
COLOR MODE
Begin with the End
When talking about image
resolution and color mode to choose
when designing, you have to think
about what the desired output will
be.
 Web? Or Print?

What is resolution?

Resolution is a measure of the amount of detail that
is stored in a digital image.
 Higher
resolution means higher quality.
 But is high resolution always a good thing.
 Lower
resolution means lower quality.
 But is lower resolution always a bad thing.
Image Resolution

Resolution is measured in PPI, or pixels per inch
(the number of pixels contained in one inch).
 The
higher the PPI, the better the quality.
 The higher the PPI, the larger the file size.

Image editing software can be used to change
the resolution of an image.
Image Output Methods

Images can be viewed in two ways


Monitors



On a screen or monitor or by printing it on paper
Monitors are low resolution devices, most display 72 ppi.
Additional image resolution will increase file size, without affecting display
quality.
Printers


The resolution at which printers can print is measured in Dots Per Inch (DPI).
Printers are high resolution devices and require high resolution images in
order to print images clearly without pixelation or blurriness.
Match The Image Quality To The
Delivery Method


Images that will be displayed on a monitor do not need a high
resolution.

Using a low resolution means smaller file sizes.

Images with small file sizes load quicker.
Images that will be printed need a higher resolution.

Images with 300 PPI are better for printing on more sophisticated
printers and will produce higher-quality photographs.
What About Color Mode?


Color Modes: a mathematical model that describes the way
colors can be represented as numbers or percentages,
typically with three or four values.
There are many types of color modes, but generally you will
work with two when editing raster images.
 RGB Color
 CMYK Color
RGB Color

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RGB: assigns an intensity value to each pixel
ranging from 0 to 255 for each of the red, green,
and blue components in an image.
If all RGB values are 0, you get black.
If all RGB values are 255, you get white.
On-screen display is represented by RGB, therefore
RGB color is best used for images that will be
displayed on a monitor or webpage.
CMYK Color


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CMYK: assigns a percentage value for each of the
process inks. Cyan, magenta, yellow, and black.
If all percentages are set to 0, the result is white. If
all percentages are set to 100, the result is black.
An image should be converted to CMYK before
exporting for images that will be
sent to print.
Quiz Time
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An image is being designed that will be display on
the new company website. What color mode and
what resolution should the image have?
RGB color and 72 ppi.
A poster is being created that will have 500 copies
printed to promote the upcoming concert. What
color mode and resolution?
CMYK color and 300 ppi.