1. 2.01 Understand Digital Raster Graphics
Units of Measurement
2.01 Understand Digital Raster Graphics

2. 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
Points
Pixels
Picas
We generally pick what we are comfortable with, but in Graphic Design it should be based on need.

3. Inches
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, 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.

4. 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.

5. 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)

6. Picas 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.

7. em Space
em generally means the point size of the font in question, which is the same as the height of the metal body a font was cast on
The letter "M", on the left in Perpetua and on the right in Calisto, inside squares of one em on each side

8. Percentage
Defining sub elements of a web page as a percentage to the width of the entire web page, allowing for responsive layouts as screen sizes to change

9. Image Resolution and Color Mode

10. 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?
Teacher Note: The purpose of any business document is to convey a message. Students should make sure any images they use help them to convey their message. If the images do not make the message easier to understand, then they are confusing the message and should not be used.

11. 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.

12. 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.

13. Image Output Methods Images can be viewed in two ways Monitors
On a screen or monitor or by printing it on paper
Monitors
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.
Teacher Note: Graphics displayed on a computer monitor can be set to 72 PPI because most monitors will only display 72 PPI. However, you need higher resolutions for printing images. 150 PPI is sufficient for desktop printing; 300 PPI for high quality printing. However, the larger the PPI, the larger the file size will become.

14. 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.

15. 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

16. RGB Color
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.

17. CMYK Color
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.

18. Quiz Time
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.