UNITS OF MEASUREMENT 2.01 Understand Digital Raster Graphics

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.

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  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.

Em Space  An em space is a term derived from the width of the capital "M" on a metal character block used with early print presses, similar to the blocks shown in the picture on this page.  used to define the current point size of the font.  For example, a 12-point type has an em space of 12 points, which also means each space is 12 points.

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.

 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 Resolution

 Images can be viewed in two ways  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. Image Output Methods

 On-Screen Resolution: 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.  Print Resolution: 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. Match The Image Quality To The Delivery Method

 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 What About Color Mode?

 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. RGB 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. CMYK Color

 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. Quiz Time